Home Forums Hunting & Shooting Gunsmithing Strengthening forend

I'm pillar bedding and then glass bedding a rifle. I'm going to build tape up on the barrel and bed the channel so it's free floating.

It's a factory wood stock. I want to keep the forend from bending around so much. I've read about people milling in carbon or aluminum shafts and then bedding the channel. I'd imagine 3/4 of that is they are readily available for free.

Has anyone ever just laid in some carbon fiber fabric under the barrel? I'd imagine it'd work. The one big downside is that if I screw this all up, that isn't coming out....

Any thoughts?

Thanks!

Would help some but the stiffness really comes from the composite structure. Lay up carbon flat. Not so stiff. Take the same amount and lay it up as a box, foam or air core. Now you have something. You can see the same thing with paper rolled into a tube. I like carbon arrow shafts, already made up and I have a lifetime supply from repairing arrows for 4-H.

Nighthawk beat me to it. The tubular shape of the arrow shaft is inherently structurally strong; carbon fibre merely packages this strength in a very light material. As regards "I screw this all up, that isn't coming out.", that'll be equally true no matter which route you take!

Get the latest issue of Rifle magazine. There's a pretty good article in it that addresses this very subject. I'm not 100% in agreement with the author, but then again I rarely agree 100% with anybody- but he covers the basics pretty well.

I will have to look at that... who is the author?

Can't say for the current ones but when Browning introduced the BBR in the late 70's they had a piece of u-shaped aluminum channel inletted into the forearm.

Aluminum... the answer to the stock builder question no one should be asking...

I worked in the Browning Gunsmith Shop during the time the BBR was rolled out, I saw thousands of them.

Gil Sengel. Like I said, pretty fair article, but I got the feeling he isn't a pro in the strict sense of the word, but more a good reporter on the subject.

And I have seen a ton of broken/cracked fore ends on them. In late winter here it is ridiculously dry indoors and the aluminum does not give when the wood shrinks around it. Because the shrinking wood is not a uniform piece it shrinks around the aluminum and focuses the forces from the inside out to the inside corners... cracks happen...

Thank you, the name rings a bell.

Besides the aluminum channel in the forearm, the BBR was not a design I was very impressed with. Definately not a worthy successor to the Safari/Medalion/Olympian rifles which preceeded it. Kinda like Browning's post'64 in a way, how they've survived and even have a following is beyond me.

To be fair, the BPS, Buckmark, and Clitoris are good designs...

If the BPS were a good design why were they recalled shortly after introduction for trigger, safety and cracked stock issues. I repaired hundreds for these issues, modified the trigger mechanisms, cocking pieces and glassed the locking lugs they're just a mass produced tube action and not a very high quality one at that. You'd think that Browning aiming for the upper end of the sporting market could come up with something much better than that.

What pump shotgun isn’t a “mass produced tube action”? I’ve seen far less BPS problems than I have 870, Mossberg, and M12 problems.

Remington probably makes as many 870s in a day as Browning imports BPSs in a year...

I have quite a bit of experience with a number of BPSs over the last 25 years without issue... so maybe they got it right in the end?
😉

If the wood stock isn't stiff enough to hold shape, throw it away and get a decent piece of wood. I have never had an issue with the forearm of factory wood stocks being flimsy. Tupperware (injection molded stocks) that's a different matter.

If I needed to stiffen a forearm, the best way is to use a solid carbon fiber pultrusion rod bedded in epoxy with chopped glass added to thicken the epoxy.



All the fibers run the length of the rod so it has the maximum stiffness. I'd use at least a 3/8" diameter rod, 1/2" would be better.

An embedded rod or tube probably won't do as much for stiffening as will a layer of CF on the barrel channel (forming itself into a channel). But that would tend to cause problems when the wood shrinks and swells, while the CF does not.

I mistakenly typed BPS, the shotgun is a good design and not one requiring much in the way of repair. What I meant to post was the BBR the replacement for the Safari/Medallion/Olympian.

I agree with you.

Strange as it might seem, hollow forms can be stronger than solid forms.

That makes way more sense and I agree.

That is probably true, but way too esoteric an argument in this bailiwick...

the hollow form has more surface area ,+ that makes it stiffer

Not in any engineering that I have seen...

In general, stiffness increases in wood as a function of the width multiplied by the square of the depth and all calculations flow from the cross sectional area of the "beam."

It is true you can lighten a structure a great deal by coring it... provided you increase the depth of the beam enough to make up the losses in cross sectional area.

I would love to see an example of a homogeneous beam less stiff then a cored beam of identical material and external dimension.

Yeah, the solid would be stronger but not by much. The outside edge of the beam, furthest from the neutral point is where tension and compression are the highest (and where spreading over area comes in). Tension and compression diminish the closer to the neutral axis. I would guess by square law but I don't know.

Anyway the gory details don't make much difference in strengthening a forearm beyond a solid beam will add a lot of weight with little gain in stiffness.

Sorry, but your answer proves you do not understand how it works... My previous post should give you an idea, but if you do not understand it instantly there is an issue with your background and you might need some help figuring it out. You are WAY off base with what you propose. The solid would be MUCH stiffer. You have to take advantage of a cube function to gain much by coring and that requires an increase in depth externally.

A solid beam fore end cannot be matched by a hollow beam unless you add significant depth.

And do not gloss over the fact many circumstances find serious value in balance in the weight in the fore end...

If you'd actually paid attention to what I wrote you would see that I'm agreeing with you and saying the same thing except in a more generalized way. We don't all work with just wood. As far as weight and balance goes, my closing sentence is a pretty clear hint that it is a major consideration.

Okay, starting with the start and working down the line...

The solid would be stronger... but by a LOT... not the "little" you suggest. Would be happy to play the math for you to understand...

You do not understand the concept of squares versus simple multiplication... period. It is huge.

Bullshit! A solid bean can add little weight, might even lose significant weight, but solids do not mean an increase.

Looking at the "Range" in math terms shows your statement is so far out there it is beneath ridiculous.

So, please, carry on!

You obviously have no understanding of what I wrote, or pretend so, so there's no point in going further.

Bending Resistance - Hollow tube vs. Solid Rod A 3 page pdf

This part of your statement is correct. It is the extreme fibers that take most of the load. Hence the thicker the beam, the stiffer it gets.

A hollow form OF THE SAME WEIGHT will be stiffer because the extreme fibers will be farther apart. However the inner fibers, the "core" keep the extreme fibers from collapsing.

pal, added a link to my last post which makes for a nice explanation of what's going on. Not sure if we're on the same page but the material on one side of the beam is all in tension and the material on the opposite side is all in compression. How much is a function of distance from the neutral axis. (an exponential)

I understand EXACTLY what you wrote and the pdf you posted.

What I wrote explains why your answer is a goofball answer in the situation of a rifle fore end. Got it?

With the same weight in the same material you can make a tube stiffer than a solid rod. You will notice I stated that is a function of the fact deflection in the same material is a function of the depth of a beam squared multiplied by the width. The deflection resistance is higher in a tube of equal weight because its depth is greater...

Now, to do that the tube has to be significantly larger in diameter. A fore end is only so large. In the same outside dimension ( the ONLY valid case in a fore end) the more carbon fiber you put in there the stiffer the fore end will be, period!

If you engineered an intricate web of carbon in the fore end you can save weight and it will be stiff enough... but voids will make it less stiff, period.

I know you understand...

Henceforth refer all engineering questions to Sitka. (Just kidding. Really.)

some one said a fluted rifle barrel is stiffer than no flutes? more surface ? it would surely be lighter how can lighter be stronger I don't know makes my head hurt to think about such things.

If a fluted barrel is the same weight as a non-fluted barrel and the same bore diameter and length it will have a larger diameter and will be stiffer.

As we get close to solid, we gain very little.... that is why birds have hollow bones.
That is why your fishing pole is hollow.

I am not an engineer not even real dam smart.
A pipe is stiffer than a similar OD solid.
The pipe will resist deflection better, until it
fails, which willeads be catastrophic. The solid willike
bend much easier, but will take more effort to have a total
failure.


For use as a stock stiffener, a good tube will be stiffer, lighter,
and will not be exposed to the forces that would ruin it.

Had a cool old FN Mauser custom 300 Win Mag back in the day with a really nice stick of walnut, it was bedded and floated and began to warp to the side a bit, took it to my 'smith, he milled out a channel in the forend, placed a 6" solid aluminum piece of square bar stock in the channel with epoxy compound, immediately placed the rifle in a vice, used some other attachment to push the forend straight with the barrel, let sit for a couple of days, it was still perfectly straight when I sold it.

At least you provided the disclaimer.

NO! The pipe is not stiffer than a solid bar of the same diameter.

Reading this thread I believe many are confusing stiffer with stronger.
They are not the same.

A 1/4" glass rod is stiffer than a 1/4" steel rod, but the steel rod is stronger.

A solid bar is far stronger then a hollow tube of the same diameter, but the tube will come back straighter if it's bent unless it's bent far enough to kink.

A bar takes more force to bend, but doesn't return to straight as well, ............. alloys being equal between the two.

Welded pipe is often made from 1018 steel and so is hot-rolled as a rule.
If anyone want to test this to be sure, (and not have to believe when they see on the internet my post included), just go get a 1" diameter water pipe (called 3/4" in the plumbing industry) and a 1" hot rolled steel rod. Get them both 4 feet long.

Now clamp them 1 foot from the end in a vice on a heavy duty bench or put them into a buried pipe in the ground 1 foot deep and pull. See which one you can bend easier.

The pipe will flex with just a little effort and come back to straight (or mostly straight.) When you go past the point it can resist, it will kink and break over.

The bar will not bend easily at all, but when (or if) you do get it to bent, it will stay bent about 50-60% of whatever bend you put in it.
Try it yourself and see.

None of this is related directly to the OP question, but may explain the debate so it's easier to understand.
Some are saying "stiff" when they mean "strong", and vise-versa

Young's modulus is the stiffness and for a given material, comparing different shapes of the same weight, the modulus will generally be proportional to strength.

In the elastic region we sometimes call this a spring where in Hooke's law, the stiffness is proportional to the spring constant.

For the same material, comparing hollow tubes to solid cylinders, stiffness is a very good way of comparing strengths.

In accuracy, the stiffness is what counts. Recoil does not break guns, it bends them.

You cannot make an object stronger or stiffer by removing material. Using hollow tubes and flutes allows gains in strength and stiffness relative to mass, not diameter. A solid cylinder of a given outside diameter will be stronger than any tube of that same diameter assuming like material composition. The thicker the walls of a tube, the stronger the tube- again, given the same outside diameter. When the walls get so thick that they touch in the center and you now have a solid cylinder, it has become as strong as possible at that diameter.

True, but fluting allows one to increase OD without an increase in weight.

Rifle barrels are not center-loaded... it is the weight of the barrel itself and the action of pressure behind the bullet straightening the barrel.

That causes the barrel to vibrate as the pressure pulse moves down the barrel..

Yup.

I went through all this with a BC stock and it stiffens the fore end but there was still flex through the action area. I just decided to live with it but if I were to do it over again I wouldn't. I would get a new stock instead or just buy a V-Block bedding cradle and inlet that in. The full length ones stiffen the action and magazine area too. But for the cost and time for this better to sell and start over.