Barrel Deflection

[47WillysGuy]

Barrel deflection, after action bedding, what’s the max deflection between stock and barrel and where’s that reading taken? Close to the action, mid barrel, or at the barrel end?

 

[rijndael]

Bedding checking gauge fixture

This is a pretty clever 3D printed bedding checker made by a talented guy in Iowa. In the past, I've used a magnetic base dial indicator but find this one to be much handier, quicker and more versatile. Having used it for a while now, I'd sure recommend it for anyone wanting to use the dial...

forum.accurateshooter.com

 

[Badbob]

I'm interested in this as well. Stress Free bedding revisited. I just rebed my BR gun after taking measurements from the tip of the stock to the barrel using the fixture above. Which, as side note, is much easier to use than the magnetic indicator that weighs a few pounds. My front action screw, when loosed, showed .010" of defection. Definitely out of spec. So I rebed the action. Failed again, but a little better .007" deflection on the front bolt, the rear tang bolt showed did not move. Obviously my technique is flawed (thanks Boyd!). so now I'm researching a better technique. Surgical tubing? Electrical tape? Alex Wheeler gravity only method?

Here is where I'm hung up. If I secure the barrel in the channel to keep it centered using tape wrapped around or building a temporary holding bed, won't that induce stress on the stock? If I zero my dial indicator on the tip of the stock while the gun is vertical (scope off) and then lay the gun horizontal like it will sit on the rest, just the weight of the barrel compresses (for lack of a better word) into the stock .015"! Maybe the wood in my laminated stock is fatigued! I watched a Cortina - Speedy video and noted that Speedy beds the gun while it is sitting in the bags he intends to shoot the gun in. I'm wondering if for the very reason of letting the weight of the action/barrel naturally deflect the stock.

Anyhow . . . off to Brand X big box store to get more tape and try again. I'd appreciate any thoughts. I'm very curious about how Alex Wheeler does his gravity only method. Support the action in a barrel vise, upside down, so the stock rests ON THE action? I have no clue.

 

[jackieschmidt]

I might get flamed for saying this, but the only true stress free bedding is a properly done glue in.

When using screw fasteners to secure to dis-similar materials together, you can end up chasing your tail.

Using dial indicators when dealing with non metallic materials, (wood), can often be an exercise in futility.

In short, I think you are over thinking this. When you do your bedding, just be sure that the only thing holding things in place is the natural weight of the barreled action. It is a good idea to support the stock in the same manner as it sits when you are shooting it.

 

[Badbob]

I might get flamed for saying this, but the only true stress free bedding is a properly done glue in.

When using screw fasteners to secure to dis-similar materials together, you can end up chasing your tail.

Using dial indicators when dealing with non metallic materials, (wood), can often be an exercise in futility.

In short, I think you are over thinking this. When you do your bedding, just be sure that the only thing holding things in place is the natural weight of the barreled action. It is a good idea to support the stock in the same manner as it sits when you are shooting it.

Thanks Jackie . . . so would you say you can glue in over a not-so-stress-free bedding job? I did check the bedding with my dial indicator before separating the action and stock. I inserted and torqued the action bolts and then check the forearm tip. Neither bolt move the indicator--she was locked in. But once I separated the two and cleaned up the trigger well and drop port, then I got .007" release on the front bolt.

So it sounds like you are not a fan of doing the bedding job with the action suspended off the barrel in a barrel vise?

 

[X Count]

Maybe I'm doing it wrong but I just wrap tape around the barrel at the tip of the forend and in front of the chamber. The tape centres the barrel in the channel and I can add more wraps to increase the clearance on either end. That way the only stress is the viscosity of the bedding compound pushing against the action.

 

[Badbob]

Maybe I'm doing it wrong but I just wrap tape around the barrel at the tip of the forend and in front of the chamber. The tape centres the barrel in the channel and I can add more wraps to increase the clearance on either end. That way the only stress is the viscosity of the bedding compound pushing against the action.

Thanks for the reply . . . I'm going to try this. and see how it turns out. the only difference is that I used 5 minute epoxy to build a little bed for the barrel at the forend. I'm going to drop it in and let if gravity do its thing. I'll report back on how "stress free" the job turns out.

 

[AlNyhus]

Obviously my technique is flawed (thanks Boyd!). so now I'm researching a better technique. Surgical tubing? Electrical tape? Alex Wheeler gravity only method?

Here is where I'm hung up. If I secure the barrel in the channel to keep it centered using tape wrapped around or building a temporary holding bed, won't that induce stress on the stock?

There's many things, by themself or together, that could be the cause of that much movement. Much of this is subtle, hard to photograph and even harder to explain.

For barrel support when the bedding is curing, I've had good results by finding the balance point of the barreled action and placing a narrow wrap of tape or an 'o' ring at that point.

There's more, of course.....

 

[X Count]

Thanks for the reply . . . I'm going to try this. and see how it turns out. the only difference is that I used 5 minute epoxy to build a little bed for the barrel at the forend. I'm going to drop it in and let if gravity do its thing. I'll report back on how "stress free" the job turns out.

What's the theory behind using epoxy to build a bed? With tape you can adjust your heights easily by adding or removing a turn to the point where you can get the whole action "floating" just above the inlet in the stock and you achieve a thickness of bedding compound between the action and stock.

 

[Jonnyofalltrades]

Getting less than 3 thou deflection on screw in bedding is something that is a lot harder than it sounds. If I just use gravity or a rubber band to pull the action down into the epoxy, sometimes it doesn't sink down into the proper place in the stock. If I use the screws and torque it down, at some point I will start reintroducing the stresses in the bedding that I am trying to eliminate.
My method(2 cent discount! Today only!) is to make certain the epoxy is thin enough to allow everything to settle in. Then screws are put in with little to no torque. Then a few gentle wraps of rubber, to help gravity pull everything down to where I want it.
Warming everything up seems to make it all work better. My shop is usually pretty cold.

 

[Badbob]

What's the theory behind using epoxy to build a bed? With tape you can adjust your heights easily by adding or removing a turn to the point where you can get the whole action "floating" just above the inlet in the stock and you achieve a thickness of bedding compound between the action and stock.

the reason I did it is to ensure the barrel is perfectly centered, left to right, between the 4" forearm. I build the stock and I cannot say that the barrel channel is perfectly centered so I don't want to roll it with tape. When I bed it, I will double-check the action is centered and the pic rail is level with the bottom of the forearm. the stock does not have a rudder so making sure it is straight, level and true is important for consistent tracking in the bags.

 

[AlNyhus]

Getting less than 3 thou deflection on screw in bedding is something that is a lot harder than it sounds. If I just use gravity or a rubber band to pull the action down into the epoxy, sometimes it doesn't sink down into the proper place in the stock. If I use the screws and torque it down, at some point I will start reintroducing the stresses in the bedding that I am trying to eliminate.

All good points. The answer is...it depends. -Al

 

[Badbob]

Getting less than 3 thou deflection on screw in bedding is something that is a lot harder than it sounds. If I just use gravity or a rubber band to pull the action down into the epoxy, sometimes it doesn't sink down into the proper place in the stock. If I use the screws and torque it down, at some point I will start reintroducing the stresses in the bedding that I am trying to eliminate.
My method(2 cent discount! Today only!) is to make certain the epoxy is thin enough to allow everything to settle in. Then screws are put in with little to no torque. Then a few gentle wraps of rubber, to help gravity pull everything down to where I want it.
Warming everything up seems to make it all work better. My shop is usually pretty cold.

What do you use to thin Marine Tex? I'm going to try it tonight just using the gravity method. I'll report back.

 

[Badbob]

All good points. The answer is...it depends. -Al

The marks are your balance points? Perfectly balanced or do you leave some weight in the rear so the action can settle into the stock?

 

[Jonnyofalltrades]

What do you use to thin Marine Tex? I'm going to try it tonight just using the gravity method. I'll report back.

I've never used marine tex, so I don't know how it acts.
My method for getting the epoxy thinner isn't by adding solvent. I could imagine that causing funny shrinkage.
Usually just using fresh product and getting it really warm makes it as runny as I would ever want. Spoiler alert, sometimes sets up really fast if you do that.

 

[LVLAaron]

Pro Bed 2000 solves a lot of problems. It shrinks less than marine-tex / acraglass.

It's thick.. and I add some thickener to it, so it doesn't run. A little work with a heat gun before application makes it workable. It's a very slow curing product, so a little heat doesn't hurt.

 

[Jonnyofalltrades]

I find that the whole thick vs thin subject sort of comes down to how much clearance you have in between the stock and the reciever, and how comfortable you are with the barreled action maybe not being sunk into the stock the exact same amount as it was prebedding. Thicker is sure nice to work with.

 

[Sniperhandle]

I've never used marine tex, so I don't know how it acts.
My method for getting the epoxy thinner isn't by adding solvent. I could imagine that causing funny shrinkage.
Usually just using fresh product and getting it really warm makes it as runny as I would ever want. Spoiler alert, sometimes sets up really fast if you do that.

Jonny,

What solvent do you use?

 

[DaveTooley]

I find that the whole thick vs thin subject sort of comes down to how much clearance you have in between the stock and the reciever, and how comfortable you are with the barreled action maybe not being sunk into the stock the exact same amount as it was prebedding. Thicker is sure nice to work with.

I like a lot of room also. Just lets the epoxy flow easier. I use a Quick clamp to pull the action into position. If it wants to spring back because of lack of flow I leave it on for 15-20 minutes then remove it. Then gravity takes over.

 

[Jonnyofalltrades]

Jonny,

What solvent do you use?

Sorry, no solvent. I just warm everything up to get it runny.