How thick should bedding compound be?

[Doodaddy]

Particularly with wood...it moves. Also, as we know, the barrel moves when fired, as do scopes. Ever seen a scope very close to a barrel? I've shown customers the mark on top of the barrel left by the scope and barrel coming into contact with each other, and still be able to slide a $ bill between the two, freely. The look on their face is one of enlightenment. The mark looks like a small wear mark. That has to be hard on optics but also tells us that stuff moves when a 60,000psi explosion happens in there.

Obviously, the person claiming on another site that the muzzle can only move about a half thou has never seen this and it raises question to his claim.

I've personally never liked the aesthetics of seeing a barrel channel large enough to encompass two barrels like I see on many benchrest rifles. I always chalked it up to them wanting absolute clearance no matter what barrel they swap to and that made plenty sense to me. I suppose it could be easy peace of mind with the barrel floating since there would be no question that a quarter inch of space is sufficient.

My bench rifle looks to have about thirty thousandths of an inch clearance between the channel and the barrel. Is that enough in your experience?

I'm not shocked about the scope movement. I've never had one so close to the barrel though.

 

[mwezell]

I've personally never liked the aesthetics of seeing a barrel channel large enough to encompass two barrels like I see on many benchrest rifles. I always chalked it up to them wanting absolute clearance no matter what barrel they swap to and that made plenty sense to me. I suppose it could be easy peace of mind with the barrel floating since there would be no question that a quarter inch of space is sufficient.

My bench rifle looks to have about thirty thousandths of an inch clearance between the channel and the barrel. Is that enough in your experience?

I'm not shocked about the scope movement. I've never had one so close to the barrel though.

I like to use a nice, consistent .030" on hunting rifles, but on BR guns, I don't mind there being more. On fiberglass stocks that I know I'm going to paint, I use heat shrink tubing on the barrel and bed it into fiberglass in the barrel channel to achieve the consistent gap...when that size gap is what I'm after. It cures fast, works and sands easily and does the job nicely. Wood is more tedious unless done on a cnc mill to follow the contour of the barrel. Some people feel the extra space aids cooling. I'm sure it does to some degree but I'm not sure its a substantial enough amount to be significant.

Some people also judge the craftsmanship by the wood to metal fit along the barrel channel. As Boyd has mentioned, that theory is out dated if your primary goal is how it shoots. IMO, it's harder to maintain an even, small gap than to make it seem seamless, as the top edge is what matters most where it meets the metal. It could be just about anything below the stock line, where it's hidden.

To each their own, but I much prefer the stock never touch the barrel. Exactly how much gap that takes is dependent upon the barrel and stock, but .030 is what I consider to be a safe amount without looking bad.

Here's a pic of a hunting stock with .030. It'll look better when I finish the barrel, as it's still in the white. The gap will be less apparent when the metal is dark.

 

[Doug]

Thickness?

Your original question was does "Thickness Matter"
NOPE - Only Quality!!

Today, I had an opportunity to check out a professional bedding job on a buddy's RFBR rifle. I was surprised to see that the Devcon coating was only about 1/32nd in thickness on average. A nice smooth compound layer, but in one area I could see the wood grain peeking through. The XIII action bolts directly on top of the aluminum pillars too. Is this considered normal or good workmanship?

PS: When I do a bedding job on my personal rifles, my goal is to put in at least a 1/8" to 3/16" layer of bedding compound. Lately, I began covering over the aluminum pillars with Devcon, so that the action does not make direct contact with the pillars themselves. Would like to hear from those that do this work professionally, or have experience at it. Thanks in advance, ... John


Posted this on another website as well.

 

[center22]

Your original question was does "Thickness Matter"
NOPE - Only Quality!!

If that is so, ... What is your interpretation of "Only Quality"?

 

[Doug]

Quality?

I use the Duck Test!
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck!

Maybe Read the Above posts to see if you have a Duck

 

[Pete Wass]

Now Tin

As bedding shrinks???? I suspect Devcon is likely the most widely used compound. The published shrinkage is .06% there Pete. I'll give you a case of ELEY if it's possible for you to measure how small that is on a 1/4X28 screw thread , or any other popular size.

How do you know all Smith's use the same compound to bed with? I have had one rifle glued in come loose because the bedding shrunk and seen two or three others over the years do the same. I have personally had two rifles that came to me from Smiths with two or three threads on the front Action screw, both of which eventually did not hold the action fast to the bedding and became teasers, accuracy wise. I believe what I experience, not what someone writes in a paper. Wouldn't hurt nothing for Smiths to put 7 or 8 threads on an action screw, would it?

Pete

 

[tim]

How do you know all Smith's use the same compound to bed with? I have had one rifle glued in come loose because the bedding shrunk and seen two or three others over the years do the same. I have personally had two rifles that came to me from Smiths with two or three threads on the front Action screw, both of which eventually did not hold the action fast to the bedding and became teasers, accuracy wise. I believe what I experience, not what someone writes in a paper. Wouldn't hurt nothing for Smiths to put 7 or 8 threads on an action screw, would it?

Pete

Welllll, long story short, how the hell do you know why those glue in's failed? Could have been improperly
catalyzed compound, old compound, or more likely guns the have gone through a lot temperature change.
That said, most modern compounds have similar shrink rates, rarely more than 1%.
2 or 3 threads are less than ideal but that action ain't goin anywhere unless they used silly putty.

 

[Pete Wass]

The point is

Welllll, long story short, how the hell do you know why those glue in's failed? Could have been improperly
catalyzed compound, old compound, or more likely guns the have gone through a lot temperature change.
That said, most modern compounds have similar shrink rates, rarely more than 1%.
2 or 3 threads are less than ideal but that action ain't goin anywhere unless they used silly putty.

if the screw threads bottom out before they are able to fasten the action to the bedding - - well, I guess you could see that, eh? In the case of the shrinkage, if a rifle performs well initially, then , over time does not and it is found that the front action screw is thread binding, couldn't one assume that it is the shrinkage of the bedding that caused the problem? As I've said, I've seen this happen more than once and with other people's rifles as well as my own.

Pete

 

[Pete Wass]

How about going all the way to a $20 John?

Agreed ... recently pillar bedded my X3L barreled action into a Lidgard Zebrawood stock. When tested, I can easily slide five one dollar bills (when held together) between the barrel and stock channel. Brent does very nice work.

Haven't had an opportunity to test the bedding in my friends rifle, but hope to do so by Wednesday. Will update. John

Pete

 

[center22]

Pete

Hello Pete,

I only had "five" one dollar bills in my wallet, for testing. This hobby has kept me extremely poor. LOL

Hope you and your significant other are doing well. Right now, it's "hot as hell" in south Florida ... and I've lived here for 51 years! Can't wait for weather that resembles winter.

All the best, ... John

 

[tim]

if the screw threads bottom out before they are able to fasten the action to the bedding - - well, I guess you could see that, eh? In the case of the shrinkage, if a rifle performs well initially, then , over time does not and it is found that the front action screw is thread binding, couldn't one assume that it is the shrinkage of the bedding that caused the problem? As I've said, I've seen this happen more than once and with other people's rifles as well as my own.

Pete

Pete,
You're the guy that can fit and chamber a rimfire barrel. You, i assume can also use a dremel tool and cut 1-2 threads off a screw. This really ain't complicated.
Me, that's why I use a guy like Tom Meredith. Been doing it almost 40 years. Great bedding, perfect screws every time.

 

[Pete Wass]

I havbve no issues with my Merideth Stock

Pete,
You're the guy that can fit and chamber a rimfire barrel. You, i assume can also use a dremel tool and cut 1-2 threads off a screw. This really ain't complicated.
Me, that's why I use a guy like Tom Meredith. Been doing it almost 40 years. Great bedding, perfect screws every time.

I agree with you, His work is superb. I have fit an cut several barrels Tim, all have worked so far. I have also lapped a couple of bad ones that now shoot pretty well also. Some think it can't be done but guess what - - -

Pete

 

[center22]

Original Poster Update

Update:

In the early morning hours, before our club practice match yesterday, I had an opportunity to set up a dial indicator on my friends rifle in an attempt to check the bedding quality. I was instructed to hold the rifle upright, during the testing procedure, but I had difficulty with the large magnetic base sliding downward and not holding well on the S.S. barrel. So I altered my testing procedure somewhat, by setting the rifle upside down in my wooden homemade cleaning cradle. With the front of the stock resting on each side of the yoke, at an upward angle, with the barrel suspended freely below. I then affixed the magnetic base to the barrel just forward of the stock. The dial indicator was adjusted to contact the center of the stock, about an inch back and the needle set to zero.

I then had my friend use his screwdriver style torque wrench to loosen the rear screw and re-torque it again to his normal setting, which was about 25 inch pounds. The needle hardly moved and when re-torqued it remained at zero. Things were different with the front action screw. I asked him to loosen it gradually until it moved around .015" and had him stop. At that point, I asked him to re-torque the front screw to 25 inch pounds and the dial indicator returned to zero as well. With this preliminary test, the bedding quality appeared good to us, but I'm not certain this test alone was valid. Because wood has a tendency to move (shrink or swell) with heat and humidity, and my friends rifle had been stored in an air conditioned environment over night.

Recommended he return his 45X Competition scope back to Leupold to have it thoroughly checked out. He told me that when he first got the scope, he did attempt to adjust the turret knobs to zero them out. Unlike older Leupold scopes that have three small set screws to perform this procedure, the Competition models are much more challenging and problematic in this area.

To see if my friends problems could be related to poor shooting skills (LOL) I suggested that he shoot my most accurate rifle in the match that day. He agreed to the offer, and was shooting my Rocky River Barn rifle. With ten unlimited shooters competing, my friend placed 2nd in the aggregate, kicking my butt by 10 points (3rd place) and a bunch of X's in the USBR match. So, ... we therefore have proven two things, it is not his poor shooting skills, nor his rest setup, that are causing flyers/flippers and poor accuracy with his rifle. In the mean time, he is going to put a 36X Sightron scope on his rifle. John

 

[Boyd Allen]

Revised because I skimmed your post too quickly and did not pick up that it was your rifle and not his that he shot so well with.

You seen to have let the tail wag the dog when attempting to test his rifle's bedding. If you need to, tape the base to the barrel to make it more secure than the magnet alone. Basically you did not do the test properly. One of my someday projects will be to make a clamp setup that resembles a low torque rifle vise, to clamp the indicator stand rod and top to a barrel.

 

[Pete Wass]

Might this movement indicate

Update:

In the early morning hours, before our club practice match yesterday, I had an opportunity to set up a dial indicator on my friends rifle in an attempt to check the bedding quality. I was instructed to hold the rifle upright, during the testing procedure, but I had difficulty with the large magnetic base sliding downward and not holding well on the S.S. barrel. So I altered my testing procedure somewhat, by setting the rifle upside down in my wooden homemade cleaning cradle. With the front of the stock resting on each side of the yoke, at an upward angle, with the barrel suspended freely below. I then affixed the magnetic base to the barrel just forward of the stock. The dial indicator was adjusted to contact the center of the stock, about an inch back and the needle set to zero.

I then had my friend use his screwdriver style torque wrench to loosen the rear screw and re-torque it again to his normal setting, which was about 25 inch pounds. The needle hardly moved and when re-torqued it remained at zero. Things were different with the front action screw. I asked him to loosen it gradually until it moved around .015" and had him stop. At that point, I asked him to re-torque the front screw to 25 inch pounds and the dial indicator returned to zero as well. With this preliminary test, the bedding quality appeared good to us, but I'm not certain this test alone was valid. Because wood has a tendency to move (shrink or swell) with heat and humidity, and my friends rifle had been stored in an air conditioned environment over night.

Recommended he return his 45X Competition scope back to Leupold to have it thoroughly checked out. He told me that when he first got the scope, he did attempt to adjust the turret knobs to zero them out. Unlike older Leupold scopes that have three small set screws to perform this procedure, the Competition models are much more challenging and problematic in this area.

To see if my friends problems could be related to poor shooting skills (LOL) I suggested that he shoot my most accurate rifle in the match that day. He agreed to the offer, and was shooting my Rocky River Barn rifle. With ten unlimited shooters competing, my friend placed 2nd in the aggregate, kicking my butt by 10 points (3rd place) and a bunch of X's in the USBR match. So, ... we therefore have proven two things, it is not his poor shooting skills, nor his rest setup, that are causing flyers/flippers and poor accuracy with his rifle. In the mean time, he is going to put a 36X Sightron scope on his rifle. John

Uneven bedding? If the bedding is flat, why would the barrel rise .015"?. I have seen a fair number of Leup Comps that had to go back. I guess for the difference in cost between them and a March they are a pretty good value but I would as soon have a Weaver 36 X I guess. They seem to be able to handle Rimfire guns OK. 30 Cal HBR and VFS rifles will tear them up. I have a Brackney frozen Leup Comp 40X and I trust it. It has crosshairs only, which I don't like much.

Pete

 

[Boyd Allen]

Note my revision to my previous post.

 

[Pete Wass]

Oops, I missedf this one John

Hello Pete,

I only had "five" one dollar bills in my wallet, for testing. This hobby has kept me extremely poor. LOL

Hope you and your significant other are doing well. Right now, it's "hot as hell" in south Florida ... and I've lived here for 51 years! Can't wait for weather that resembles winter.

All the best, ... John

The Spousal Alternative is doing OK. A couple of minor skeletal related issues since we got back but otherwise fine and dandy. We are having an interesting Spring/Summer here in Maine, so far. Gets up to 80 or so during the day and back to the low 60's in the evening. I am finding I much prefer 70 to 75 in the evening and don't mind 90 any more during the day . I'd prolly do ok down by you, eh?


Best wishes,

Pete

 

[Doug]

Shade Tree Gunsmith

I tried using a magnet to hold my dial indicator to the barrel & indicate off the stock with not much luck!
The solution was to clamp the Dial indicator to the stock & indicate off the barrel if that makes sense?
I put my rifle in the rest like I would shoot it!!
Next I took a 4 inch 2X4 and drilled a 1 1/8 hole and split it down the center.
I clamped this over the stock at the forearm so the barrel free floated under.
Next I clamped my dial indicator to this block & indicated on the barrel just in front of the forearm!

PS I have two simple blocks - one 7/8 for my sporters and 1 1/8 for my heavy guns.
Also the gunsmith who told me about this test measured with the rifle vertical.
For many reasons after testing I felt this was invalid.

 

[Boyd Allen]

I am not sure that you guys get what is being tested for, and why it should be done in the vertical position.

 

[Pete Wass]

Am I wrong in that

The bedding should be flat front to rear and rear to front? It would seem to me that ..015" of compression over the rear pillar is excessive, of course a little bit back there would be exaggerated on the other end but .015" ?

Pete