Home Forums Hunting & Shooting Gunsmithing Acraglas

What's the difference between a Brownells accurizing kit and the gel accurizing kit.

The gel is a thicker viscosity and most people find it a bit easier to work with because it isn't running and dripping all over the place. Other than that the two products are virtually the same in the end result.

Thanks.

Yep. The gel is like working with peanut butter while the regular stuff is like chocolate syrup. Should I have posted this in the Cooking section?

RH

Give devcon plastic steel a try it the best I have seen

I have used several types/brands of epoxy, and to say that one is the "best" depends on the application. As others have mentioned, texture and viscosity are two significant characteristics. Of course, personal preference is important. Acraglas Gel is not my first choice for a bedding compound. I find it more like taffy than peanut butter, sticky, and it is a bit softer than others because it is filled with nylon particles. Devcon steel has a gritty, grainy feel to it, and may rust under some circumstances. For a steel filled bedding compound, Brownell's Steel Bed is my preference. It's smoother than Devcon, and it may be stainless, but I'm not sure. Devcon aluminum putty is another good bedding compound, but I don't know how well it holds up to heavy recoil. It used to be very popular with the benchrest crowd. For a general nice handling bedding compound, Marine-Tex grey is good stuff. Original Acraglas is too runny for general bedding, but that very characteristic makes it useful for applications such as a final skim coat. It seems to harden well in thin layers, something that is not the case with all epoxies. You can also customize its texture and color by adding your own fillers and dyes.

Epoxy - the greatest invention since sliced bread and canned beer.

Paul

I have started to like Brownells Steel-Bed also due mainly to the one-to-one mixing ratio.

Devcon also sells their product with stainless steel particles in it if you're worried about rust forming.

Epoxies are funny stuff sometimes. The higher tech stuff is not designed for most of us mortals since the mixing ratios are EXTREMELY critical to strength. Brownells has done extensive tests and studies over the years and all of their Acra products are designed to be less critical in that area.

You can't really go wrong using any of Brownells Acra products, Devcon liquids or putty, or Marine Tec.

You would be smart to stay away from the Home Depot stuff like JB Weld...IMO. I know guys who have used it, but based on my own tests I won't. It's brittle, it shrinks, and it's far more susceptible to crumbling than the above named products.

Rick, looks like we're pretty much in agreement.

I'm not familiar with tests that Brownell has done, but it's always been my understanding (and experience) that original Acraglas is pretty fussy about precise mix ratios. I always try to follow the manufacturer's instructions to the letter. Since I often use small quantities of Acraglas, and because it's so danged expensive, I usually measure it out with syringes absent the needle. Very accurate and no waste.

You can also make leftover mixed epoxy last awhile by putting it in the freezer, although it will still harden, just slowly. A day or two seems to be the max of its useful life.

Paul

That's why I said that sometimes epoxy is funny stuff.

Some brands dictate that you measure by volume...others are by weight.

As far as I know, Brownells Acra products are about the only ones designed specifically for bedding rifles. Not to say the others don't do just as good a job...but it's always nice to know that you can call Brownells about the stuff and get specific answers as they relate to bedding a rifle. Try doing that with Devcon or Marine Tec.

My gunsmith only uses Devcon,it's get hard as steel when it completely cures.

Devcon has always been my favorite...but I'm slowly turning towards Brownells Steel-Bed because of the easier mixing ratios.

I use Devcon 5 min epoxy to secure the pillars prior to bedding.

I'm not trying to be a jerk here, but when I've observed a gunsmith hook his thumbs in his suspenders and announce "Ah use Brand X in my shop, exclusively", I usually go elsewhere. It suggests to me that the man isn't particularly flexible or innovative, and he's trying to justify himself by suggesting to the customer that his way is the best or only way. In my experience, the best gunsmiths are inveterate experimenters, with a variety of tools and materials in their shops.

And I'm not clear on why "hard as steel" should be a criterion for a bedding compound. If that were the case, top gunsmiths would be milling bedding blocks out of solid steel. Plus, some metal filled epoxies have a tendency to chip or "sugar".

I'm not a gunsmith, but one time, in what turned out to be an expensive experiment, I bedded a rifle in Devcon titanium putty. It worked well, and talk about hard! My goal was to save a bit of weight, but my sense is that much of the weight of the bedding compound comes from the epoxy base, not just the metal fill. It didn't seem all that light. I also found that the titanium had a rather short working time, less than I've experienced with Devcon steel and aluminum putties. An expensive learning experience!

As an aside, there's a well-respected accuracy gunsmith in this area who charges extra to add a skim coat to a bedding job. IMO, this is wrong. All epoxies shrink, some more than others. The main purpose of a skim coat is to produce a close fit after the main bedding has cured. A gunsmith should offer only top quality in a functional area like bedding. Again, JMO.

Paul

Paul,

"Properly" bedding a rifle is not quite as simple as many would have you believe it is. There are many factors involved and the material being used is but one of them. IMO, proper technique is far more important than what particular bedding material is used.

Some of the poor techniques that can result in a less than satisfactory job no matter what brand is used (not in any particular order.):

1. Poor preparation of the stock that gives an uneven base for the epoxy resulting in thin and thick spots in the critical bearing areas.

2. Poor mixing of the epoxy. To include inaccurate mixing ratios, contamination of the epoxy, introduction of air bubbles from over-eager mixing, etc.

3. Too much, too little, or uneven compression used on the barreled receiver when the epoxy is setting.

4. Not leveling the stock in your vice. (Gravity Works!)

5. Not allowing the epoxy time to fully cure.

6. Not testing the bedding job afterwards with a dial indicator or an "educated hand" while loosening and tightening the guard screws and looking for movement of the barreled action.

I'm sure others could add to this list, but these are just some of the things I have been guilty of myself in the past while learning and that I have seen in others work that has come into my shop.

In addition to all of the above you can also run into problems when your bedding job includes pillars if you don't know what to look out for. The store bought pillars that have the radius pre-cut for round bottom receivers will NEVER fit all receivers properly. It is also real easy to get pillars cocked off to one side or the other which results in a less than even compression surface for the receiver and bottom metal.

All of these pitfalls are preventable...but a guy has to understand that there is a bit more to the job than just hogging out some stock material, whipping up some epoxy and slopping it in the stock, and sticking the barreled action into the stock overnight.

As for "skim-bedding" I totally agree with you if the smith is charging extra to skim bed (fix) his own bedding job. I usually recommend skim bedding those stocks that come with the aluminum bedding blocks since the blocks seldom (if ever) fit the receiver the way they need to.

Rick,

An excellent, informative summary. Your candor about learning through experience speaks well for your professionalism.

Bedding is sorta like scope mounting - not as simple as it may seem, with differences in quality of results dependent on how it is done and attention to details.

Paul

Anyone who has never screwed something up has never done much.

I was once told that the difference between a professional and an amateur is that the professional has learned how to fix/hide his mistakes.

Bedding rifles and installing scopes isn't some esoteric skill but it does take a bit of learning and understanding of what it is you are trying to accomplish.

Just a personal pet-peeve of mine...but the comment that it's "just" a hunting rifle drives me right up the wall. Bedding and scope mounting, IMO, should be done with the same care and attention to detail no matter what the rifle is to be used for so the owner is confident that the rifle is giving him all that it's capable of.

After all...shooting is allot more fun it the bullets are going where you intended them to go.

Rick:

Is there a distributer or company that sells all of the Devcon Epoxy?

Hardware stores around here carry it, but only in the 5 minute stuff. No steel or aluminum filler.

I usually buy mine at my local Rutland tool supply, but Brownells also carries it.

If you go to their web site they have a link to distributors, and also allot of good info about epoxies with spec sheets, etc.

http://www.devcon.com/

1234567,
Good point in bringing up the Devcon sold at most of the hardware stores. It is not the same as the high end devcon stuff, it will show significantly more compression and brittleness.

Rick,
What problems do you see with JB weld? It was recommended by Darrell Holland and he thinks enough of it to package it with his bedding kits. I have bedded several rifles with it (about a dozen) and not run into any problems. I have/had the tech specs on it somewhere and it compared very favorably with the better Devcon products.

As you've seen, Devcon is a big company with various product lines. The consumer-type products that you find in hardware stores are not the same as the industrial grade epoxies used in gun work.

The last time I bought Devcon (the titanium adventure) I found it at Grainger Supply. If you live in or near a city of any size, there might be an industrial supply company that carries such things. Otherwise, as Rick said, you should be able to mail order it. Last time I looked, Brownell's carries maybe one or two of the Devcon epoxies, but not a variety.

Like I said before, and the way Rick is leaning, if I wanted a steel-based bedding compound these days I'd look no further than Brownell's Steel-Bed.

Paul

I've been doing business with Brownells for over 40 years and one of the main reasons is because of their incredible customer service and knowledgeable/helpful tech people. They have been a tremendous help to me over the years whenever I had a problem or stupid question I needed answered. It's just nice to have people who understand firearms on the other end of the line and have actually done what you're having a problem with and can give you some handy pointers.

With their variety of Acra products and more recently the Steel Bed I really don't think there is much need to go elsewhere. They will have a product that will be suitable for just about anything and everything a smith would use epoxy for be it bedding or just around the shop on holding jigs and fixtures.

How well does Acraglas hold up to bore solvents? I read somewhere Acraglas will soften up if exposed to bore solvents after awhile.

Prefer Marine Tex over Acraglas myself.

MtnHtr

I guess it depends upon one's definition of "awhile."

I've also never really understood how one goes about getting bore solvent soaked into the bedding of their rifle.

A real good way to do your own tests of epoxies is to get a plastic ice cube tray and fill that sucker up with every type you want to test. Then take the epoxy cubes and soak them in bore solvents...bang on them with a hammer...try to crush them in a vice...etc.

I have been using Marine Tex from Brownells lately and I like it better than anything else that I have used and I have used about all of them...It is a 5x1 mix and thats a tad more trouble but short cuts never work best in gun making anyway..

Even with a bore guide it only takes a little bit of solvent to run down thru the front guard screw threads and into the bedding. Solvent is pretty thin and tends to migrate thru the tightest spots. I would rather have a solvent proof bedding compound like Marine Tex and not take chances. I usually place a small piece of cotton under my bore guide just in case.

Try placing a drop of solvent inside your action just in front the chamber, wait a few minutes and pull the action.

There are a few gunsmithing/bedding videos where the author states the bedding should always be checked for solvent contamination. It's more common than you think.

MtnHtr

Maybe off topic, but does anyone know the type of glue used to glue brake pads to brake shoes for cars and trucks?

This stuff seems to be heat resistant and about everything else resistant.

You ever consider turning your rifle upside down when running wet patches? Back in the dark ages when I was a 17 year old recruit at MCRD our Drill Instructors taught us that trick to keep solvent out of the action and stock of our M14's.

Wasn't it Will Rodgers that said the problem with common sense is that it ain't all that common?

It's normally a silicon based adhesive and it acts as a dampener and heat block as well as an adhesive.

Great for brake pads...but not exactly what is needed for bedding a rifle stock.

The R&D for stock bedding material was done a long time ago so there isn't much use in trying to reinvent the wheel.

Which is why I started with Brownell's products and stayed there. Decades of user feedback and adjusting the formulations to get the best results. (And you get the same formulation every time.) Not that there is anything wrong with Marine Tex and other proven by experience compounds. I just haven't found a reason to change, much less try stuff not in widespread use.

I agree...but I'm not trying to be an ad for Brownells.

As I stated earlier, any of the top of the line epoxies such as Marine Tex, Devcon or any of Brownells products will do a fine job for you.

Hell, back in the 1960's Marine Corps armorers in Vietnam even used the epoxy from AMTRAC repair kits to bed sniper rifles and a whole bunch of dead gooners can attest to it's effectiveness.

Me neither - just that they've never come up short on me and it's been pleasant to do business with them. There have been some that I'd rather not talk about.

If you look at the spec sheets for all epoxies (including Acra Glass) it will say that they "resist" certain chemicals, solvents and other substances. "Resist" is the operative word here and I guess that can be open to debate on what that actually means in the real world.

RickB,

Guess myself and others have been cleaning our rifles incorrectly all these years! How do you clean/push the cleaning rod thru the rifle when it's resting upside down in a gun cleaning cradle?

Guess all the fellas at the club/range lack common sense?

MtnHtr

Rick:

I didn't mean for using as a bedding material. Maybe I should have explained further.

My question was actually asking about it being a very strong and heat resistant adhesive, like it could be used to glue ribs on barrels, or glue double rifle barrels togather, or glue sights on.

Any place where you wanted something to stay put but wouldn't want the heat from brasing or soldering.

How does your cleaning rod know if the rifle is sitting right side up or upside down, or even on it's side??? The barrel is still on a horizontal plane no matter which way the rifle is laying.

As for your last statement, I would say yes if they can't figure out how to keep from soaking their stock and bedding material with bore solvent.

Both Loctite and Permatex (owned by Devcon) make retaining compounds that work great for those types of uses.

RickB,

You missed my question but that's okay.

MtnHtr

Does this answer your question?

I just happened to have this in photobucket but if you'd like I will snap a picture of me doing the same thing on one of my rifles and post it for you. Seriously, it ain't real hard to do and it takes care of any worries about getting solvent where you don't want it.

By the way, the Corps uses Devcon as a bedding material for the M40's.

LOL....


I've never had any need to go with a different product than Acra glass gel.. At times it's wise to mix in some powdered steel, depending on the caliber/stock etc., but it's one helluva good product..

Main thing, like RickB says, is to make sure it's fully cured (usually one full week) before using the rifle. To date, I've not had the usual solvents do any damage to the bedding, but then I don't use some of the real funky stuff either and I'm careful to clean up fully when done.

40 years, huh? WOW.. Beats me by double.. Best to ya..

Was at West Marine this morning and picked up some stuff that looks like it might be handy. It's sold under the West Marine brand name (who knows who makes it) and it's a Penetrating Epoxy kit used to seal and repair wood on boats.

It claims to REALLY penetrate deeply into the wood...and it adheres to fiberglass, cured epoxies, and all woods.

Sounds like it might work well for painting barrel channels etc.

I'm gonna do some tests and see if the stuff lives up to the advertising.

The qualities you want in a bedding epoxy (no matter which one you like) are a very low percentage of shrinking and a very high compression strength.

Stock bedding is not really subject to any shearing forces but it is subjected to compression and shock and that's where some products rise above the others.

Marine-Tex does not list either the shrinkage rate nor the compression strength...only the shear strength and tensile strength of the cured product.

Brownells lists the shrinking specs but not the compression strength of their products.

Devcon, by far, has the most extensive tech specs of any epoxy I have used. The compression strength of Devcon Titanium putty is 18,800 psi!

Not really, just flipping the rifle upside down is not failproof. I'm not saying you are wrong but I have never seen anyone clean their rifles that way especially at the range with a scoped rifle.

The Varmint Hunter Magazine, Jan 2000

Some Thoughts on Load Development - Part III by Steve Timm
What To Do If The Rifle Won't Shoot Accurately
"If the rifle has been in service for a while, take a dental probe and check that the synthetic bedding compound is hard. Sometimes sloppy cleaning procedures allow solvents to creep into the bedding. The solvents of course, attack the bedding compound and eventually leave it with a puttylike consistency. If the compound is soft or questionable in any way, then replace it"

Now before you say any more wise-a$$ comments check this out:
Bartlein Barrels on Breakin/Cleaning



Do these folks lack common sense for cleaning their rifles in the upright position? I clean my own rifles upright, muzzle slightly down and simply stuff a small piece of cotton under the boreguide/chamber area as a precautionary measure. But some folks might not know that solvent can creep into their rifle bedding and may be ruining their bedding job.

MtnHtr

Like I said, I was taught that in boot camp 45 years ago and never really knew that it was all that esoteric or unknown. Shows you how naive and out of touch I am I guess.

I clean scoped rifles like that all the time and have never really thought it was weird or difficult at all.

Now...before you say any more wiseass comments...get down and give me fifty private for insulting the Corps!

Sir, Yes Sir!



MtnHtr

See there...you do actually have a sense of humor!

I like Acraglas gel mixed with powdered aluminum and Marine Tex for the skim coats. I have never tried the expensive Devcons as this aforementioned work fine.

Mel Smart- who started what is now Serengeti used red-box acraglas and used steel wool as "rebar" in the stock. I have found that red-box acraglas with Kevlar chips added makes for a fantastic bedding job and looks good too- it's just a lot of work to cut up that Kevlar small enough to use it that way. I sent Mel a lot of it and he loved it. Used up until he died.

There's a lot of good products out there for bedding. Richard's Micro fit isn't one of them!

I'm not trying to be contentious, or shill for Devcon, but I doubt that Devcon is more expensive than the Brownell's products when you consider the cost per quantity in the standard containers of each. IIRC, Brownell's is a few ounces, whereas Devcon putty comes in one pound cans. Brownell's also sell in bulk quantities.

Epoxy ain't cheap, and if you buy Brownell's in the kits, you're paying for the packaging and little doo-dads. I'm just an amateur who does an occasional job, so the cost differential doesn't drive my preferences anyhow. I've been happy with both brands mentioned.

I've never used Micro-Fit, but thanks for the heads up.

Paul

FWIW...I believe that Devcon is the only epoxy out there with a Mil-Spec rating. I'll leave that up to each person to gauge the value of that when making their choice, but what it means to me is that their products have undergone and passed an independent battery of tests that can be viewed and evaluated as to their relevance for your intended use. With the other products you pretty much have to rely on the manufacturers advertising claims and word of mouth from users.

The trouble with word of mouth, IMO, is that you seldom know what criteria the speaker is using when claiming that Brand X is the "best." I have heard people claim that JB Weld is the greatest stuff around for bedding but when pushed for an explanation the low cost and availability seems to always be the deciding factors for their evaluation.

I've done a few with JB and never had any problems. Only reason I used it was because it was recommended to me for being easy to work with and not prone to voids/air bubbles. Haven't used it on any hard-recoiling rifles. That being said, I have a box of Devcon steel putty on my bench for a tryout.

Air bubbles and voids are the result of poor mixing and application procedures...and have nothing to do with the material being used.

This is sort of what I was referring to by "word of mouth" endorsements for a product.

I agree with the first part of your statement, but not the second. I have found that the texture and consistency of the mix do make a difference, and that's I why I developed a dislike for Acraglas Gel many years ago, because of its stringy, taffy-like texture. The thicker compounds seem more likely to trap an air bubble than the more fluid mixes like original Acraglas. One thing I have found that helps is to load your epoxy into a fairly large syringe, and carefully inject it into the bottom of the recess, gradually moving toward the top. Of course, you still have to watch for bubbles, and deal with them on the spot.

I do agree that technique matters, a lot.

Paul

I just did a Savage rimfire using Devcon Plastic Steel Putty. It costs $32 a lb. here in Canada. You can find it at industrial supply places. It works very well, and compared to fiberglass resins I've used in the past, it is a pleasure to work with. It does not flow much at all on it's own. I used my reloading powder scale to measure the putty and hardner to get the mix right. If you want to read the gory details, I documented the process here.

http://www.rimfirecentral.com/forums/showthread.php?t=223949

The specs on the Devcon are here:

http://www.devcon.com/prodfiles/pdfs/fam_tds_101.pdf

Yes, it is a bit gritty if you rub it between your fingers, but it moulds to a glass like finish equal to what is against it when it sets up. There is no doubt that is what I would use again next time.

Ron

Rick:

I have used both Devcon and JB Weld. The Devcon I used in the past was white, and 24 hour cure. I would still use it, but none of the hardware stores in my area carry it any more. I don't think it had any steel filler or any other filler in it.

JB Weld is plentiful, and I use it now. The grey kind that dries overnight.

But, although I have bedded rifles and shotgun stocks with it, I use it for another purpose.

I make knives, and I glue the handle scales onto the full tang of the knives. I also use rivets, but I use glue 'just in case'.

Occasionaly, I make a slight error and have to remove a handle. I clamp the blade, point down, in a vice and drive a chisel down between the steel tang and the handle material. Most of the time, the wood, or whatever handle material I use breaks before the glue comes loose from either the knife tang or handle, then I have to grind the glue off.

These two glues are the only two I have used that bond this well, and that includes Accuglass and all other brands of epoxy glue that I have tried, which has been several.

When I grind the handle material down to the steel, sometimes I get careless and grind too much, getting the steel extremely hot. I don't know how hot, but too hot to hold. So far the Devcon and JB have held, even after heating. IIRC, JB will hold up to 300 degrees F.

If I did this with other epoxys, and I have, including Accuglass, the knife and handle seperates before it even gets warm.

It has been my experience that very few glues, of any type, will securly bond metal, except these two. Accuglas might, but the heat resistance, for my purposes, is lacking.

Before applying the glue to BOTH surfaces, I degrease both surfaces with rubbing alcohol, and let dry.

I realize that bonding strength does not necessarily make for a good bedding material, nor the other way around, but I wouldn't hesitate to use either epoxys for either purpose, and I have and do.

As far as the 5 and 30 minute clear stuff, in either brand, for my purposes they could quit making it and I wouldn't miss it.

In a perfect world bedding should allow the receiver to do it's flexing when the shot goes off...and then let the receiver settle back to the exact same place it was before the shot was fired (every time). To do that it needs to have very good resistance to compression and impact. Shearing strength (which is what you describe with your knife handles) isn't really a factor with rifle bedding.

Just about all the epoxies will withstand temporary heating to 250�-300� F without any problems.

The five minute epoxies are handy for "tacking" pillars in place so you can move right on to bedding without having to wait overnight for the pillars to be solidly anchored in place.

I've been reading this thread with interest and don't want to hijack it, but does anyone know where to find a good tutorial on bedding? Thanks!

Anyone tried the "blackmax" cyano-glue?

This is the best one I know of. In it there is a discussion of the pros and cons of the different bedding materials, and release agents.

http://www.6mmbr.com/pillarbedding.html

Ron

Thanks, Ron. Now THAT'S a good tutorial. Unlike the one-size-fits-all-exclusively smiths I mentioned in an earlier post, this guy explains the how and why of what he does and recommends. His comments about soft brown bedding compounds and not trying to get by on the cheap with epoxies are especially worth reading and heeding.

Also, Rick made a good point about mil-spec standards for epoxies.

dennisinaz, with due respect to what appears to be have been a close relationship between you and the deceased founder, and with the current owners of Serengeti, if I was prepared to spend thousands on a high-end rifle and learned that the makers were bedding with Acraglas and steel wool "rebar", I would go elsewhere post haste. Ditto on the kevlar fill.

It's not that homebrewed epoxy fillers don't work, I've used them myself, but for the main bedding I wouldn't trust fillers added to the mix. I'd be concerned with uniformity, among other things. I have much more confidence in manufacturered products with the filler added by the factory, to consistent specifications.

As the saying goes, YMMV.

Paul

All jokes about "military intelligence" aside...the advantage to Mil-Spec testing is that they conduct the tests under every conceivable environmental condition on the planet. Having a product tested in extremes of temperature, humidity, altitude, etc, can be very helpful when making a decision.

Devcon has been making epoxies for the military and the aviation/aero-space industry since the 1950's when the technology started...and that says something to me.

Everyone should make their own decisions, but having all the specs available sure helps you to make "informed" decisions.

Exactly!

So, does Brownell's manufacture their own epoxies or merely repackage someone else's? If someone else�s, who�s and what product?

As for JB weld, I've used it once for a temporary job on an action that was waiting for another mcmillan. Compared the specs with the various devcons and as I recall the compression strength was less though still substantial and shrinkage numbers the same or less.

I doubt very seriously that Brownells actually "makes" anything they sell. Like most businesses they contract for the manufacture of their name brand products using their specs.

It says allot about Brownells that they carry, in addition to their own Acra Brand, both Devcon and Marine-Tex.

Where did you find the compression strength of J-B Weld? Their web site lists the specs...but there is no spec for compression strength. Their specs also say it has "zero" percent shrinkage. That's actually a bad thing for rifle bedding because you are constraining your receiver in the stock.

Perhaps compressive strength?
Tensile strength: 3960 psi
Adhesive strength: 1800 psi
Flexural strength: 7320 psi
Compressive strength: 10733 psi
Shore D hardness: 85 (1 week)
Shrinkage: 0.0%
Tube size (each): 28.4g, 100mm x 20mm.

As to shrinkage I recall the others I looked into went further than one decimal so I am thinking if JB went went a couple more decimals there might be a number.

I was going by the info on their web site which does not list a compression strength that I could find anywhere.

http://jbweld.net/products/jbweld.php

Acra-glas comes with a little pouch of fiberglass flock. This is to thicken it up and give it more tensile strength. Mel told me that he found that using Kevlar or carbon fiber in lieu of the fiberglass make it that much better. I'll put a mix of Acra-glass and kevlar fibers up against your Devcon any day!

Mel showed me his method for using steel wool to bed and seemed to be the cats a$$. He said that the bedding held up very well and was easy to make look good- remember, he was only bedding walnut stock- not synthetic like we mostly do today. I'm not sure that uniformity has anything to do with a good bedding job. I have seen excellent bedding jobs that comprised three different materials. Nothing uniform about that!

Manufacturers give us what we want to pay for, not necessarily what is best. I suspect that if you added a pouch of kevlar fibers instead of fiberglass flock, you would price the bedding kit out of reach of many who use it.

Although I don't use that method anymore (too time consuming) I never had a problem with it. Mel was an old guy 10 years ago and maybe just didn't want to come into the 21st century!

All this has me wondering just how much compressive strength do you need? Walnut has always worked pretty well except for splitting (which is another issue) with a compressive strength on the order of 7,600 psi for American grown species (USDA Forrest Service). Now Devcon specs its 2 Ton Clear Epoxy at 11,000 psi and I'd suppose it's a good quality standard grade epoxy.

Seems to me that getting the mixing ratios as close to perfect as you can (and mixing thoroughly) to get the best mechanical properties is more important than what you stuff into the mix. (I see that Brownells says adding powdered steel to Acraglas Gel increases compressive strength a whopping 10 percent.) That does help to get a consistency that lets you apply it for best results. For product specifications I'd be more interested in shrinkage and lot-to-lot repeatability. Once I get a product to perform with a specific technique I don't want anything to change.

I've used Acraglas and it works fine, but I like using a 2:1 slow curing liquid epoxy... I mix it thoroughly, then add Cabosil as a thickener to turn it into a gel. I add whatever color I want and it's good to go.

I do use JG Weld for attaching scope bases/screws to the receiver. It's a relatively weak epoxy as epoxies go, and is perfect for this application.

The supposed attributes of different products have little meaning unless they were all tested using the same criteria...and that criteria is relevant to the intended use.

Say epoxy A's compression test used a 6 inch thick block and epoxy B's test used a 1/16 inch thick block and each of them withstood 10,000 psi before failure. Which one is stronger and more appropriate for rifle bedding?

Some serious gnat straining going on here...

When someone recommends brand X as being great I've found that it's often instructive to find out how they arrived at that conclusion so you can make your own decision as to how that relates to your particular needs.

If that's "straining gnats" then I guess I'm a first class "gnat strainer."

I imagine there is an ASTM standard for testing epoxy, there is for everything else. Of course there's no guarantee that stated figures were arrived at through the standard method, but a reputable manufacturer would be foolish to cook the numbers.

In any event compressive strength is compressive strength no matter what size if the material is homogeneous and the stress is evenly distributed and there are no unaccounted for external variables. (What you want in a testing standard.)

"...and the criteria is relevant to the intended use."

That's a good point, impact resistance and creep would be concerns in choosing a bedding compound. That's where experience with a material is probably the best measure as what you'd expect to be the testing standard would be quite different than the conditions in a bedded rifle. A good reason to stay with materials that are known to work well.

Getting the ratio of resin to hardener as exact as possible (and thorough mixing) is important. Mechanical properties fall off quickly as you diverge from the proper ratio, more or less quickly depending on the system. I think that's where people get poor results with a known-good product.

+1 on that, Brad!

However...since we're already in the gaack, I just wanted to say a few things. I'm a mechanical engineer and work in the composite material industry and the company I work for has developed many different polymer materials for use in reinforced composites, i.e. carbon, glass, Kevlar, etc. fibers and I was in charge of the testing group for some time, so have experience in testing in compression, tension, and shear of all types of composite materials. What I want to relate to everyone is compressive strength is not really what you're after here. What you want is a material with a high compressive modulus. In simple terms, modulus is defined as the stress divided by the strain at any given point. Or in other words, it is the slope of the linear portion of a stress-strain curve that you would get when you perform a compressive test on any material. I don't want to bore you by going into further engineering details on this since if you're really interested you can find this info on the net very easily I'm sure. To illustrate why compressive strength is not what you want I would tell you that I can give you two different materials, each with the same (equal) compressive strength, but one material will compress (strain) under load significantly more than the other before it fails. For bedding materials, we want a very stiff (meaning strains or compresses very little) material so that upon firing the rifle, the bedding material will move (strain) as little as possible. If it moves alot, we might as well not have bedded it at all. Typical unreinforced epoxies usually have a compressive modulus of around 1-3 Mpsi. For comparison, 6061 Aluminum has a modulus of about 10Mpsi, Titanium alloys around 16Mpsi, and steel around 30Mpsi. So you can see that if you combine any of these metallics in particle form to an epoxy, you can increase the modulus quite abit and given the same volumetric quantity for each, you'll increase the modulus more by using the steel. However, you'll also increase the weight more by using steel than by using aluminum. Also, since we are dealing with a particle reinforced material, the strength of these "metallic composites" will still be dominated by the epoxy matrix, thus you won't see a very large change in the strength of the material.

We can also use non-metallic fiber particles in a similar manner to increase the modulus of the bedding material and also to keep the weight down. One must remember that the fibers we're talking about such as E-glass, carbon fiber, and kevlar, by themselves have pretty much zero compressive strength and stiffness...sort of like pushing a rope. Therefore, typical properties of just the fibers themselves are given in terms of tensile strength and tensile modulus, but if these fibers are reinforced with an epoxy matrix, we would expect the compressive properties to be similar to the tensile properties for continuous fibers. So, for comparison purposes, I'll note that the tensile modulus of glass fibers are around 10Mpsi, carbon fiber can run anywhere from 8Mpsi on up to 100Mpsi, with most typical carbon fibers used in industry around 50-60Mpsi. Kevlar modulus runs around 18Mpsi. Since it would be very difficult to use long, continuous fibers for bedding a rifle, most people use chopped or milled fibers (very short) to add to the epoxy for bedding, thus the mention by many of using chopped Kevlar or glass to add to their bedding epoxy. Since we can't use continuous fibers for bedding, and since we can't align the chopped fibers in the proper orientation to take advantage of their strength in their axial direction, the benefits in modulus that we get by using chopped fibers in a bedding epoxy are not quite what you would expect based on the modulus numbers given above. While we will see some increase in modulus by using these fibers, it probably won't be much better than if you add a mettalic, since a metallic is a homogenous material and has the same properties in all directions, unlike the fibers. This is why you don't hear of everyone using chopped carbon fibers in epoxy for bedding compounds even though carbon has a much higher modulus than the other materials mentioned.

As a side note, you can also see from the numbers above the reason why we all like the carbon fiber reinforced stocks since the use of carbon fibers in continuous form greatly "stiffens" the stock due to it's very high modulus. The stock makers can orient the fibers in the correct direction and thus take advantage of carbon's high modulus. Coupled with carbons light weight, it's the best material by far for this application. Since the amount of bedding compound you're adding to the stock doesn't amount to much in terms of weight, whether or not you use metallics or non-metallic particles makes little difference. For this reason, I went with stainless steel particle reinforced epoxy when bedding my .416 Rem.

Sorry for my long winded writing, but I hope some find it useful and that this doesn't stir up too much of a hornet's nest. Perhaps everyone is asleep by now!

No matter how much compression strength the epoxy or glass bedding has, it still amounts to a very thin layer of bedding compound on top of a piece of wood (assuming you are bedding a wooden stock), which has an even lower compressive strength.

Even if the epoxy or glass doesn't compress, the wood under it acts as a compressionable cushion, which amounts to about the same thing. The only advantage to glass and epoxy bedding that I can see is that you have an almost perfect and stress free molded fit between the wood and metal. If the wood warps, so will the thin layer of bedding compound that is bonded to it, with resulting uneven stress placed on the metal parts.

In my opinion, that is why piller bedding works so well. The action is resting on two metal pillers, and even aluminum has greater compressive strength than bedding material, and the action parts are held securely by steel screws.

No matter how much the wood and bedding material shrinks, expands, shifts, compresses, cracks, breaks or warps, the action is still resting securely on the pillers.

As I said earler, I'm not trying to promote Devcon, so it isn't "mine". And it isn't a question of the fiberglass flock that comes with the Acraglas kit vs. whatever filler somebody else wants to add, I simply stated my preference for compounds that come with the filler already mixed, i.e. putty. For a metal based epoxy I have come to prefer Brownell's Steel-Bed, because I like the texture and the fact that it is filled with stainless steel.

I've been fooling with this stuff since the 1960s, when original Acraglas was the first or certainly the most touted bedding material. Later, it fell out of favor as a PRIMARY bedding material, and most builders of competition rifles went to Devcon or a similar material. I'm not aware of any such rifle makers or stockers who currently use original Acraglas for primary bedding areas. Do you know of any smiths who build HP competition, or benchrest rifles, who use original Acraglas? Military armorers? If you are happy with it, that's fine. I still like and use original Acraglas with and without fillers, but not as a primary bedding material.

Paul

Of course but remember what you're coupling the force into. Would modulus make a meaningful difference so long as it was the same or greater than the stock behind the bedding? (Walnut on the order of - wood is so variable - 1.7Mpsi, your shoulder a bunch less and not a fixed point) And elasticity? Does it matter that the bedding compresses tiny a bit so long as it does so consistently and returns to its former dimensions?

Useful stuff I think. The better you understand the materials, the mechanical system you're building, and the better you define what that system should do, the better the results.

Brad, all of the good products seem to work fine. But I don't know everything, sooo far from it. I'm interested if anyone can make a case for something different.

123...,

I think you're getting to the meat of the nut, just what do we want the bedding to do. I want the recoil lug to transmit force to the stock evenly across its entire surface. A complete, even contact between the lug and the stock. I want consistency, the contact points between the action and the stock should be exactly the same from shot to shot. For pillars I want changes in stock dimension and action screw force to not strain the action. Other than that who cares what the bedding compound does.

These quotes above, I think, have hit on what is actually going on and what the bedding should do. The modulus of the bedding compound is probably not that important since the forces will be transmitted back to the wood or synthetic stock, but we do want the bedding to be at least as good and hopefully better than the stock material to minimize any movement and maximize the transfer of forces. It seems pretty obvious to me now that there are a wide array of materials and methods for bedding stocks and most people seem to be having good success with their respective method, so I suppose that illustrates just how non-critical the actual material used for bedding truly is. It's more critical how the rifle is bedded as opposed to what material is used to bed it.

I'm not trying to take away from the discussion, just opining that there's really little real-world difference between most epoxies for the very simple/non-demanding requirement of bedding a rifle.

I've got far more expereience with epoxy than I care to remember. Once upon a time I installed commercial grade epoxy floors for an enormous variety of uses. Everything from fully grounded epoxy flooring for McDonald Douglas aircraft assembly to the Anhueser Busch Brew House floor to Operating room floors, and everything in between.

Said all that to say, I'm seriously familiar with epoxy! Few realize, but there are only three makers of epoxy in the entire world. The stuff is sold and re-labelled/blended as other products. JB Weld, for instance, is really a trowel-on epoxy made to be mixed with sand for chemical resistant applications. I know that because I troweled hundreds of gallons of the stuff in slit trenches at a Dow Corning Chemical plant. Would add, the way we bought our epoxy was in 55 gal drums!

Bottom line, nearly ANY epoxy is rigid enough to give perfect results in a rifle... the application just isn't very demanding. Pillars in conjunction with nearly any decent epoxy will get the job done.

My .02

Sorry Brad, but do a google search for Manufacturers of Epoxy and you will find FAR more than three companies just in the USA...let alone the entire world. China has a ton of them.

I would also disagree that rifle bedding is a "low-demand" application considering the force it must withstand from the recoil of a high powered rifle cartridge being delivered in milliseconds.

Can't say the current state of affairs as to actual mfg's... a few years ago there was just three. There are a LOT of "blenders" that call themselves manufacturers but aren't.

As to a rifle's bedding being a high demand application, I think that's nuts...

One caveat to Brad's message: Cheap, off-brand stuff may not be so good. Who knows how old the resin is, how it was stored, how many hands the resin has been through, or if it was rejected for poor quality somewhere along the line and sold off cheap. Same for hardener components. And who knows if the formulator put together the system looking for good quality or just used the cheapest available components. Good enough for the dollar store and usual consumer use but that's about it. Stick to reputable brands.

Absolutely... tried to convey that point but prolly wasn't too successful. Devcon, Acraglass, Marine Tex, the chit in a five gallon bucket in my garage that's been around fifteen years and has been used on a couple dozen rifles... all good.

This stuff just isn't that hard, but some seem determined to make it so...

So it seems the only concensus is there is no concensus. With that out of the way has an epoxy every been produced/blended for the specific needs of bedding rifles or are we just using what makes us feel warm and fuzzy inside?

I prefer the devcon putty as number one because Im not comfortable with the 5:1 mix on Marine Tex. I have bedded most with JB weld and do not feel the need to dremel everything out and have not seen any problems through a few thousand rounds. I know a couple dozen rifles does not match the thousands a professional is doing but it seems if something was going to go bad based on the bedding product it would have popped up by know.

Ultimately, within reason, the guy doing the bedding is probably more important than the compound selected.

I don't think it can be said any better than that.

Well, Devcon has been manufacturing (not just blending) epoxy for 50+ years...JB Weld is a family owned business that's been manufacturing their own epoxy for over 30 years...should I go on? By the way...JB Weld was invented by a guy in his home shop and his first customers were auto repair shops. Your statement that it was originally designed to be mixed with sand for chemical resistance is total hog-wash.

I will agree that technique is huge part of the game...but not all epoxies are appropriate for all jobs. Devcon alone manufactures a vast array of different types of epoxies designed for specific applications.

You have no idea what you're talking about...

Well...you were totally wrong about the number of companies manufacturing epoxy, and you were totally wrong about JB-Weld...so who is it that's uninformed?

http://jbweld.net/aboutus.php

http://www.devcon.com/corporate/index.cfm

Checkmate!


Brad's move!

MtnHtr

PS. Humor intended post!

You just don't get it... JB weld IS NOT mfging epoxy... they're buying the raw materials and blending them. They can technically call it "manufacturing" because they're changing the raw material, but they're not doing the initial refining. They're buying the raw material and repackaging it.. so yeah they're a manufacturer, but they're buying their raw material from a supplier who's getting it form the source manufacturer.

That's about the silliest argument I have heard in awhile. Sorry... but JB-Weld, Devcon, and many others do "manufacturer" their own epoxy products.

There are 100's of companies world wide that manufacture the raw materials to make epoxies. These companies DO NOT make or sell epoxy...they just make the materials that other companies (like JB-Weld and Devcon) use to make epoxy. Dupont is probably one of the largest and well known of these companies.

There are also 100's of companies around the world that buy those raw materials and formulate and manufacture the finished products that are sold every day around the world under various brand names.

Do you think McMillan actually manufactures the fiber glass used in their stocks...or that Remington makes the steel used in their rifles?

Gents, this has been an interesting and informative discussion, but it's getting pretty deep, at least for me.

Now, I've just been doing something I should have done long ago, making up a finish test walnut board. I've made four sections, and rubbed in Acraglas and G-1, while heating it. Going to try a variety of coats, then oil finish on top. This stock finishing business is akin to alchemy. Maybe I should wear a pointed wizard's hat, and apply the finish by the light of a full moon!

So much to learn.

Paul

So you're saying they're refining petroleum into epoxy, correct?

As old Struther Martin said to Paul Newman..."What we have here is a failure to communicate."

Brad...Epoxy that we buy is a formulated product made of various ingredients, not a product refined from petroleum. Like just about every manufacturer of any product in the world, the companies that "formulate" and sell the finished product do not manufacture all the ingredients used in their finished product...and the companies that manufacture the ingredients to make epoxy do not normally manufacture and sell epoxy as a finished product.

Each company making and selling epoxies has their own formulas they use to produce the finished product...and they formulate them to meet the needs for specific purposes. The epoxies you used for floor coverings were formulated to be highly resistant to abrasion and cracking so they would hold up under people walking on them all day long. Other epoxies are formulated to be totally sterile and non toxic so they can be used in food processing equipment. Heat cured epoxies are formulated to be more heat resistant than those that cure at room temperature, etc, etc.

Epoxies, just like paint, are formulated for specific purposes. The paint you use in your living room wouldn't perform too well on the engine block of your car.

http://en.wikipedia.org/wiki/Epoxy

My information is obviously old... when I was buying epoxies by the thousands of gallons there were three primary suppliers in the world. We bought from what we thought of as "blenders"... obviously things have changed!