bedding compound

[milanuk]

Belzonia, yeh, I have worked with it quite a bit, since we are in the Marine Machine Shop Business.

If you listen to the hype presented by the product representatives, you wonder why the just don't make an entire vessel out of the stuff.

I work in a hydro-electric dam, and that stuff gets used extensively for cavitation repair in the water passage - both on the runner blades and for the steel liner for the passage itself. There are a few spots where it seems like there literally *is* more Belzona than steel

Seems like it'd be kind of spendy to use for bedding, although I've never compared the prices per unit. Do the other products normally used for bedding (Devcon, Marine-Tex) have similar shelf-life i.e. don't use after this date?

 

[Charles E]

A left-field thought:

Everyone seems to be caught up in the notion that the bedding material should be "hard." Maybe that's not entirely correct. The bedding should keep the action from moving. Far as I can see, that's all. "Hard" is equated with "no movement." That may be true, but even if so, you don't need 5 inches of "hard" to keep things from moving.

I once bedded a couple Remington 540s with two "hard" pillars which contacted the action, and did the rest of the bedding with Devcon Flexane, a pourable rubber. (Aside: even after curing, Flexane will take a set, so you have to keep the action from moving, esp. under storage.) Anyway, those two rifles shot exceptionally well. OK, .22 RFs don't generate a lot of recoil.

IIRC, Browning, when they first introduced the Boss system, used a vibration-dampening material to bed the action. Most "hard" materials do not dampen vibration, just the opposite.

How about this: Best, If somebody could figure out how, would be to have just enough immovable material to firmly position the action under recoil & handling stresses. The rest of the bedding would be some material which helped isolate the vibrations in the stock (tuning fork) from the barreled action.

Thoughts?

 

[frwillia]

A left-field thought:

Everyone seems to be caught up in the notion that the bedding material should be "hard." Maybe that's not entirely correct. The bedding should keep the action from moving. Far as I can see, that's all. "Hard" is equated with "no movement." That may be true, but even if so, you don't need 5 inches of "hard" to keep things from moving.

I once bedded a couple Remington 540s with two "hard" pillars which contacted the action, and did the rest of the bedding with Devcon Flexane, a pourable rubber. (Aside: even after curing, Flexane will take a set, so you have to keep the action from moving, esp. under storage.) Anyway, those two rifles shot exceptionally well. OK, .22 RFs don't generate a lot of recoil.

IIRC, Browning, when they first introduced the Boss system, used a vibration-dampening material to bed the action. Most "hard" materials do not dampen vibration, just the opposite.

How about this: Best, If somebody could figure out how, would be to have just enough immovable material to firmly position the action under recoil & handling stresses. The rest of the bedding would be some material which helped isolate the vibrations in the stock (tuning fork) from the barreled action.

Thoughts?

A rifle firing is a dynamic event. There are several web pages that have 2D dynamic models of this event which, if not perfect, clearly illustrate that there is a lot of gyration going on when the rifle fires. The barrel has waves, humps, ripples, and moves all over the place with the wave behavior modes combining via supperposition to create a remarkably complicated motion. Action and stock react during this process, but most importantly the mounting in the stock (bedding) controls the conditions under which the process begins. This is a fact of life. The key to accruacy is to have it happen the same every time if subjected to the same stimulus (your favorite load). Once the bullet leaves the barrel, other factors take over, but until the bullet exits the muzzle and is beyond the influence of the resulting gas expulsion, the dynamics of the rifle firing and internal ballistics are what influence the future flight of the bullet.

The response of any dynamic system is determined by the stimulus, initial conditions, and the inherent dynamic characteristics based on system design (floated barrel, stress free bedding, heavier barrel, etc.).

What one is trying to control with bedding are the initial conditions. The theory is that if the same system starts it's response to an identical simulus with the same initial conditions it will respond the same every time. A chaotic system is a deterministic system for which initial conditions cannot be known well enough to predict it's behavior a useful distance into the future. One doesn't want a chaotic system as a rifle, so bedding is important.

Introducing compliance, additional spring rates, into the system increases the complexity of the system, introduces more degrees of freedom in a situation where less is better. Doesn't mean it can't work, but bedding material that is soft with respect to the forces involved, or which can take a set, or chanve over time with solvent exposure, should not, in theory be better than one that is stiff and will not inelastically deform under the stresses of firing or storage.

YMMV.

Fitch

 

[Boyd Allen]

If I remember correctly, Browning used steel pillars and hard rubber bedding for their rifles that came with the BOSS tuner/brake. I believe that they said that it made the tuner work better.

A couple of more things about the dynamic nature of rifle bedding....Early on, when Mike Walker was in charge of the custom shop, they found that if the bottom 180 degrees of actions were not a true cylinder, that for their most accurate cartridges, there was a decrease in accuracy. That resulted in the a change in order of operations for the 40XB-BRs. They were hardened before the OD was ground and polishing was kept to a minimum on their bottoms. Because of this, it was impractical to use stamped lettering, which is why you will see applied rather than stamped lettering below the ports of these models. Some years back, well after Mr. Walker had retired, I spoke with the then new head of the custom shop, asking him whether that was still being done. He did not know what I was referring to. Another example of provision for controlled, repeatable action in bedding can be found in Harold Vaugn's book.

 

[Charles E]

What one is trying to control with bedding are the initial conditions. The theory is that if the same system starts it's response to an identical simulus with the same initial conditions it will respond the same every time. A chaotic system is a deterministic system for which initial conditions cannot be known well enough to predict it's behavior a useful distance into the future. One doesn't want a chaotic system as a rifle, so bedding is important.

Problem is, initial conditions vary. The biggest factor in variance for vibration amplitude, according to Vaughn, is variation in bolt thrust. Bolt thrust can vary for a number of reasons.

 

[chino69]

does anyone know the weight ratio for acraglas?

al

Al,
It's 50/50 by volume. Glop equal amounts on a mixing pad and mix.

 

[chino69]

There is a product manufactured by the Enecon Corporation that comes close to Belzona. It's called Duralloy. It has a compressive strength of 13,500 psi, Izod impact strength of 1.2 ft. lbs./in, and a Shore D hardness of 86. It can be machined, drilled and tapped. This company makes quite a few new age epoxies for almost any type of application. I considered using Duralloy to bed an action but have been hesitant as you only have about a 12 minute working time. Might try it on a factory cheapy down the road.

 

[alinwa]

Al,
It's 50/50 by volume. Glop equal amounts on a mixing pad and mix.

Not Acraglas gel, Acraglas....it's "4:1 by volume ONLY, not weight" which makes it unusable for me. I go through quarts of the stuff weighing it but some lots heat, some don't and Brownell's plays 3 monkeys.

al

 

[Charles E]

column B:

If bedding is so critical, why do barrel-blocked guns, with the action floated, shoot so well? Please don't tell me it's due to the bedding quality used to secure the block.

 

[chino69]

Not Acraglas gel, Acraglas....it's "4:1 by volume ONLY, not weight" which makes it unusable for me. I go through quarts of the stuff weighing it but some lots heat, some don't and Brownell's plays 3 monkeys.

al

You're right; I was referring to Acraglas gel. I've used Acraglas gel with the powdered stainless additive with very good results.

 

[Boyd Allen]

Charles...really? Come on now. Have you never bedded a rifle action and seen an improvement in accuracy? Is your question real or rhetorical? The issue is shot to shot consistency of barrel vibration during firing. Within this general area, such things as damping come into play as well. I have absolutely no experience with barrel blocks in stocks, but I have been told that for rail guns putting various materials between rails' blocks and the beam or plate that they are bolted to can improve accuracy, as well as between block and barrel.
Boyd

 

[frwillia]

column B:

If bedding is so critical, why do barrel-blocked guns, with the action floated, shoot so well? Please don't tell me it's due to the bedding quality used to secure the block.

I always looked at the block itself as the bedding.

Fitch

 

[Charles E]

Charles...really? Come on now. Have you never bedded a rifle action and seen an improvement in accuracy? Is your question real or rhetorical?
Boyd

Sorry, I was unclear. I'm back on the "hardness" of the bedding compound issue. Far as I can tell, the purpose of bedding is to ensure the action is secure to the stock. Part one of that is "It doesn't move." Pretty easy to achieve, and you don't need rock-hard material to do that. Part 2, if there is one, would have to do with transmission of vibration. As far as I know, there isn't any proof on one this, but there has been a movement by some toward stocks that dampen vibration -- wood, Jim Borden's newer Rimrock, etc. If you're so inclined in this direction, why wouldn't bedding material, or dual-bedding material, be of equal interest.

I brought up barrel blocks, in their various incarnations, because they are yet another way.

 

[frwillia]

Sorry, I was unclear. I'm back on the "hardness" of the bedding compound issue. Far as I can tell, the purpose of bedding is to ensure the action is secure to the stock. Part one of that is "It doesn't move." Pretty easy to achieve,

This is a bit of a nit, but ctually, that's nearly impossible to achieve with out gluing the receiver to the stock, and even then given the spring rate of the wood it might move a little. One can get it to return to the same place it started from close enough as won't affect accuracy (which isn't the same as not moving), but during the discharge of the rifle, especially more powerful cartridges, it's going to move.

and you don't need rock-hard material to do that. Part 2, if there is one, would have to do with transmission of vibration. As far as I know, there isn't any proof on one this, but there has been a movement by some toward stocks that dampen vibration -- wood, Jim Borden's newer Rimrock, etc. If you're so inclined in this direction, why wouldn't bedding material, or dual-bedding material, be of equal interest.

I brought up barrel blocks, in their various incarnations, because they are yet another way.

To the extent that damping material isn't perfectly elastic (in other words to the extent it doesn't return to the same place each time), and most isn't, it may not do as good a job of establishing identical initial conditions from shot to shot.

That doesn't mean it won't work, but it seems like a solution in search of a problem. They shot some 1 hole groups in the Houston Wearhouse. The reason that doesn't happen more often isn't the rifle.

Fitch

 

[Ian Robertson]

I don't know what the weight ratio is for regular acraglas. If all else fails measure out several times the correct volume of each and weigh it to figure out the ratio. In an earlier post I used the term "hard", it should have been "properly cured".

 

[alinwa]

Ian,

one of these days I hope to get myself into a situation where I need several oz of the stuff and I'll do exactly that but meantime I gener'ly only need a tiny bit and having a good scale.....

(Yup, I'm a tightwad.... what with Brownell's wanting three yearling goats and a bushel of barley for the stuff)

 

[Ian Robertson]

You can always measure and weigh the parts and then put it back in the containers.

 

[alinwa]

now why din't I think a' that?

I'm off to do it Ian

 

[MColeman]

Another reason I love West Systems Epoxy is that I take a plastic high ball cup sold in grocery stores, put it on my Dillon digital scales then turn the scales on. I put in the amount of resin I need (I always put in too much but you really mess up if you don't have enough), observe the weight of the resin, divide that by 5.2 to get the amount of hardener needed. I zero the scale then add hardener. Mix it up good, put the color tint in that I desire and add the colloidal silica until I get the consistency right then bed the rifle. Never fails and is so simple even a caveman could do it.

 

[Zebra13]

Another reason I love West Systems Epoxy is that I take a plastic high ball cup sold in grocery stores, put it on my Dillon digital scales...

Mickey,

Certainly less then a noble end for something as distinguished as a high ball cup...

Justin