Home Forums Hunting & Shooting Gunsmithing Reinforcing a sporter stock forend

I've got a sporterized M96 mauser whose stock in front of the action is pretty flimsy and makes contact with the barrel. I am going to float the barrel and want to reinforce the stock so it won't move on the forend. Do I need to imbed an aluminum rod (allthread) to stiffen it or will bedding compound along a deep channel suffice?

GarryVA had a pretty good idea.
https://www.24hourcampfire.com/ubbth.../Bedding_Actions_Which_Areas#Post4573484

Although I don't think I'd hog out the barrel channel as much as he did, but I like the aluminum rod he used to strengthen up the forend. BSA.

Yea, I'm kind of thinking that I need metal and that bedding compound won't provide the stiffness I need.

Thanks for the post.

I have hollowed fore ends to thin shells and filled them with sections of broken fishing rods bedded in epoxy fluffed with microballoons. It is extremely stiff and reduces weight...

A piece of aluminum as long as the example in the photos does not move like the wood does with temperature changes and would worry me...

Many of the light to standard sporter weight factory wood stocks I've floated have had flimsy forends. If nothing was added, you'd have to float a huge channel to reduce contact which further weakened the forend. Ideally, having an aircraft grade chassis inletted into the stock that runs from the rear tang at the wrist all the way through the forend to the front swivel stud would probably be superior to anything from an engineering standpoint. You can machine or purchase a manufatured aluminum chassis and inlet it yourself along the lines of the Accurate Innovation stock, but that would be a complete waste of money on a factory stock in my opinion.

My normal technique is to inlet and custom fit a machined aluminum stiffener that runs from the front swivel all the way through to the recoil lug at the lug mortise. This stiffener is both mechanically tied as well as epoxied into its inlet for the full length. In addition, I'll tie this stiffener through the bedding into either a machined or a poured pillar that runs from top to bottom. To maximize sealing the forend with an exact amount of float which I pre-determine, I open the forend an exact amount to leave a complete skim coating of bedding epoxy within the entire channel. This combined with pouring the shank pad so that it only extends to the knife edge balance point of the barreld receiver less stock, maximizes bedding strength and durability while minimizing the total added weight. These are techniqes I picked up and adapted from training at Quantico. My main change is that instead of using a foundation bedding with Titanium Devcon with a skim bedding of Marine-Tex, I use Marined tex for the entire bedding. This saves money and has been proven by extensive testing from quite a few of the major players to withstand severe recoil from even the big calibers.

Installing a barrel stiffener to a floated factory wood stock can greatly improve the dynamics of the wood forend. If done properly with a bit of thought, it can be done with a minimal amount of weight change. If done poorly with little thought, you may end up adding a ton of weight with little added stability and little added stiffness.

Best:)

I had the same dilema with a commercial FN 98 thin forearmed pencil barreled 30-06. I debated on full length bedding vs action only. One problem I wanted to solve was the flex in the forearm. The barrel channel was originally cut by hand and just forward of the barrel/action joint there was a lot of clearance. It was tight at forearm though.

What I ended up doing was to bed the action and halfways up the forearm. That extra clearance underneath the chamber when filled with epoxy solved the flexy forearm problem. Basically, it added a "C" shaped epoxy reinforcement. The "C" shape is very resistant to bending and flexing. I sanded a taper (about an inch or so) at the end of the epoxy to eliminate the abrupt edge/pressure point. The barrel is free floated forward from the bedding.

This worked out perfect for my rifle and it shoots better than ever.

Thermometers often use bimetal strips to show accurate temperature changes... the idea of intentionally building one in makes me shake my head, particularly for a free floated barrel. Particularly in the length involved I see sressses being built and fail to see the need for all but extreme cases of repairing bent fore ends... and there I see far better materials available.
art

I don't have access to broken fishing rods, and damn near cry should I break one of my good ones. I use stiff spine carbon arrow shafts where Art uses rod pieces. Lighter than solid aluminum or epoxy and you don't have to entomb them though it looks pretty, just glue securely. If you do entomb, adding microballoons will save a lot of weight (relatively speaking). I'm told you can get microballoons at hobby shops catering to model aircraft builders which is more convenient than aircraft supply companies or the like.

Goodwill type stores usually have plenty of cheap rods hanging about... Far cheaper than good arrow shafts. Not bedding the shafts in fluffed epoxy reduces their stiffening ability a huge amount. Doing it without filling leaves the potential for water to get into the fore end and stay there... And several other bad things.

I can assure you that those predictions are off. This has been done, and this has been used and tested on multiple applications; It works.

That particular rifle noted was used for testing and experimenting with the Ruger Compact Magnum 338RCM. The original intent was to retain and float the factory compact stock. The Compact Magnum forend was way too flimsy, with too little available space, for a scavenger fishing rod technique to be successful. You'd add too much weight and waste too much of the limited space to see any improvement. By the measurements taken, without laying up a custom shaped fiber insert, fishing rods would not fly and would be a poor choice for the intended goal.

The factory Compact wood is only so stable compared to a laid up stock with a solid fill material in the action area. No matter what stiffener material was used, it needed to support the entire forend throughout its length. This bedding technique with the machined aluminum pillars, the machined aluminum stiffener, and the mag box/trigger inlet reinforcements, turned out far stronger and far more stable than the original format while keeping the compact stock light. It ended up weighing less than a standard fill McMillan while having a very strong and stable forend that supports floating under rough use. This rifle was run hard for a year in hot, cold, dry, and wet conditions to include complete submergence. The rifle has held sight adjustments for under MOA, and the rifle holds consistent action screw torque. It has since undergone its first yearly LTI and the bedding was found to be true, straight, and stress free without needs for corrections or skim bedding. The rifle returned to a proper stress free torque, and it repeated POI back into the same MOA test groupings without needs for corrections. I think it completely fair to say that this bedding system has proven well, with this particular rifle proving to be outstanding. In addition to this rifle, it also has worked equally well on other applications prior to and after this rifle.

To add to the bedding technique, this stock was completely refinished, to include checkering, using Acraglas. Though I intend to switch to a slower curing epoxy, I�m confident, based on damage I since repaired from bashing rocks, that I obtained good penetration from the faster Acraglas. With a good coat of wax, it has held up well, for wood, during exposure to inclement weather and wide temperature swings. But, I�d like to double penetration in the future to better hold up to the more common dings and scratches I get when afield.

Outside of starting from scratch with a better piece of wood, this modified factory stock is on track to seeing many years of reliable service with repeatable accuracy.

Best:)

Interesting. I came up with an idea while staring at the ceiling fighting insomnia one night. That's to cut carbon bow building laminate strips to build a made-to-fit tapered box beam with medium density urethane foam-in-a-can in the middle. Certainly could be made stiff enough!

Over the top for most applications I can think of but I may try it some day just because.

Gary
Aluminum moves far more than wood in a simple temperature swing of 50F... We hunt in temperatures with easily 120F temperature changes and I know one rod reinforced fore end that has been shot at 109F (LA gator) and -40F (caribou)...

Rods can be as thin as needed and are far stiffer for their weight than aluminum... especially when the aluminum seperates from the wood.

I do not believe there will be huge problems with what you are doing... I think they could happen, however. The mechanics of bedded rod parts are really hard to match with bar stock aluminum...

Carbon arrowshafts are lighter, more stable and stiffer than aluminum and broken ones can be gotten for free at nearly any archery range or proshop.

If you saw how clients have dealt with my fishing gear you would understand why I have so many broken rods...

Sitka, I understand your point, but these techniques have been developed and used for many decades, going back to Fred Bear in archery. The aluminum alloy is mechanically locked but is bonded by epoxy with no direct contact with the substrate. The thermal coefficients of steel, stainless steel, aluminum alloy, and even the epoxy itself are all different compared to wood and to themselves. But there's not enough difference to shear the epoxy bond, bind the materials themselves, or bind the barreled action in hunting conditions. No bimetallic thin strips are involved and no bimetallic thin strip condition exists and therefore do not apply.

The wood substrate is completely isolated yet stalbilized by the chassis to prevent stress build up on the barreled action. The epoxy can withstand flash points to 500 degrees and the aluminum requires 3,600 degrees to melt. You could set the stock on fire, which is a pretty extreme temp change, and it should not bind the barreled action until it started cooking. I have yet to test to -40, but I do believe this is within the epoxy specs and that any movement of the substrate materials due to temp changes should not develop enough shearing to defeat the bond strength and mechanical lock.

That carbon rod/shaft scavenger technique has its place, but would have resulted in less than ideal results with this compact stock. The space was limited and the carbon fiber rod/shaft waisted the available space. Grinding solid rods flat would have been a waste of effort leaving inadequate spine. Fitting these carbon rod/shafts required an additional waist in voids to fill when trying to fit enough carbon for spine. The end results would have been too much stock removal, too little carbon added for the space, too little stiffness gained, and too much overall weight with the fill. The only way to take advantage of the space with carbon would be to inlet and fit a layed up fiber insert. I can do this, but the type of stock in this project and the measured weight savings over a machined aluminum stiffener were not enough to warrant the effort. I machined the pillars and other reinforcements, so making and using the aluminum stiffener was quick and made better use of the available space than rod/tubes. The aluminum stiffener was machined to fit the inlet and the exact barrel contour, so it maximized spine for the space available. This was a bigger bang for the effort which resulted in greater stiffness gained with less overall added weight. We are talking <MOA / sub-seven pound Ruger with a factory wood stock shooting a magnum cartridge. That is outstanding!!

I also build stickbows, so I do have a supply of carbon material to use if warranted. If you followed any of my past rifle builds, I did use carbon on a lightweight M70 416Rem that I built patterned after Shoemaker's light rifle. But in this case and in many other applications, the aluminum stiffener was the better choice. In some cases, inletting a one piece machined aluminum alloy chasis that runs from the rear tang at the wrist all the way through the forend is the best choice. I'd not do that with a factory stock.

In the end, we can only do so much as these are wood stocks that are not in the same league of stability as a McMillan. As a side note, I'm currently working on two more projects that I've had idling, both with wood. One is a Sig Sauer M-98 Mauser and the other is a completely tricked out CZ 375H&H. I'm switching from Acraglas to the West System for the stock finish. I used the West System for years when I was building paddles, but I've not used it for stock finish. Hopefully I'll get a bit more penetration with the slower epoxy.

Best:)

Gary
You are missing the big point... You say you anchor a piece of aluminum to a piece of wood at both ends and bed it in epoxy.

Aluminum is quite mobile when the temperature changes. Wood does almost no moving with temperature. When the temperature changes the two parts go in opposite directions... They have to.

Epoxy, fiberglass, carbon fiber all move about like wood.

For its weight wood is extremely strong and good wood is incredible. Aluminum run full length under an action is just asking for a problem. It creates an area between the wood and aluminum where stresses are high. Those stresses could cause sudden failures at any time, especially in the wood. I have seen a lot of broken stocks...
art

What Art is talking about is the material property called coefficient of thermal expansion (CTE). This is how much a material expands per inch per degree F (more commonly it's in metric units). The CTE of aluminum is ~4 times greater than wood and ~2.5 times greater than filled epoxy. Because of the different rates of expansion you're going to get stress which can deform the material (stock) or cause failure (at either the wood to epoxy or aluminum to epoxy interface).

Zachary!

Good Grief! I'm trying to be polite, but you're getting on my nerves. No Sitka, you are stretching theory that exists only in your head, based upon unrelated engineering designs, to equate to reality in the field when it has already been proven otherwise over decades by scores of manufacturing applications to include manufactured rifle stocks. From a pure engineering standpoint in terms of these materials used in rifles and rifle stocks; the thermal coefficients of aluminum alloy is not much different than stainless. Steel is less but still greater than wood. Even the cured epoxy itself has a thermal expansion that is as different to the wood as stainless or steel. Your lengths of carbon fiber epoxied into place DO NOT "ALL MOVE ABOUT LIKE WOOD"! They do not have the same physical properties and they do not have the same characteristics.

Neither the barreled action, a length of aluminum alloy, stainless, steel, or the epoxy itself; inletted, bedded, bolted lengthwise, or even glued into place within the wood stock, will have a difference in thermal coefficiets great enough to shear or bind the action, PERIOD! This only happens in your head. None of those materials are thin and narrow enough to bind and curl along the lines of a bimetallic strip. None have enough difference to cause high stress and shearing due to the thermal coefficients. A piss poor inletted barreled action will cause binding and high stress. It may even cause cracks and broken stocks. But aluminum alloy inletted and epoxied the entire length of a sealed straight wood stock is not going to magically twist into a pretzel and break.

Don't take this in a bad way. I greatly appreciate many of your posts, and you have some great knowledge on many things. But at times you come up with some oddball stuff that sounds good at first blush, but it doesn't match reality and proven historical Empirical data. Some of the past stuff you've posted to me as if first hand proven Empirical data, has in reality turned out to be third hand untested theory. Your fishing line cross bolts come to mind. I will machine, inlet, and epoxy into place an aluminum alloy chassis to run from the tip of the forend through the entire stock to the rear tang at the wrist. You could take that darn thing anywhere you care that humans hunt, and the thermal coefficient differences between the three materials will not be enough to sheer or bind anything. You could attempt the exact same thing with lengths of your fishing rods and you'd gain nothing, other than looking less professional along the lines of Red Green and his Duct tape.

Do you truly believe that the difference in thermal coefficients between a straight wood gun stock and an inletted epoxied chassis of aluminum alloy is great enough to bind the two materials, shear the epoxy bond, and break the stock?

Later

The fishing line cross bolt thing was not my idea... Just one I really like.

Having done more than a little playing with wood movement relative to metal I think I have a better than fair handle on it. If wood can move enough to stress a stock... it can and does... Then adding another element certainly can and will.

The fact is I have messed about with aluminum as a fore end stiffener and in fact can probably dig out the date and magazine where my father wrote about your basic idea. It would have been the '70s IIRC. There is a reason I no longer use aluminum in long lengths for stock work...

There is a reason I do not use metal to reinforce wood... Epoxy does a btter job and has fewer boundary issues. Adding another element with much greater is not the right answer in my experience.

Found an article in the October '74 issue of American Rifleman, page 31... In it he used a steel stiffener for a fore end. But it was for a serious boomer. We did a number of different things with metals. The fishing rods win hands down...

I know you are locked into your system, and I have not been particularly forceful about my disagreement... But it is borne of experience and enough failures to make it obvious which is better... and certainly faster.
art