Bedding the whole barrel

[ligonierbill]

So I bought a nice looking sporterized Mauser (8mm-06) with an especially good looking stock. A previous owner did a real neat bedding job, including the entire barrel channel. Now, I always thought that only the first few inches of the barrel, if that, should be bedded, leaving the rest of the barrel free floating or at least free of pressure points.

I'm still working on loads, but this gun groups very poorly so far. Barrel and rifling look good. It's the original military barrel, and every step is impressed in resin. Before I get out my rasp, is this a likely cause of my poor groups?

[wpsdlrg]

Impossible to say for sure. There are no absolutes with rifle bedding, only general rules, with exceptions. Fully bedded barrels sometimes shoot very well, sometimes not. In general, it is agreed that free-floating the majority of a rifle barrel has the best chance of success. I would agree with that assessment, based on my experience. However, I have a Mauser that actually is more accurate with a fairly large bedded pressure pad at the tip of the fore end. Free floating the barrel was NOT the best solution for that particular Mauser. It wears an original stepped profile military barrel, though cut to 17" (as the rifle is now a sportered carbine).

What I would do, if I were you, is carefully check how the receiver is bedded first. Mausers are tricky to bed. Make sure that there is NO possible movement of the receiver in the stock, including the bottom metal (trigger guard). If the receiver bedding is solid, I would guess (and it is only a guess) that the fully bedded barrel MIGHT be the problem - assuming that you have already tried enough load variations in the rifle to preclude the loads being the main cause for poor accuracy.

Do understand, though, that free-floating ANY rifle barrel is USELESS (and in fact, will make things worse) IF the receiver bedding is not absolutely solid. So, be sure of the receiver bedding FIRST.

One other idea: you said, I believe, that the rifle wears "an especially good looking stock". I am assuming that the stock in question is solid wood, or perhaps a laminate. My concern is that the stock could possibly be too flexible. It does sometimes happen with really slim profiled wooden stocks, but not that often. Just something to consider, that's all.

[ligonierbill]

Thanks. FWIW, I have only tried two bullets. Barnes 160 TTSX do 3", not a shotgun but far from acceptable. In other calibers, I've done extremely well with TTSX. The other is Sierra's 175 ProHunter. It looks like a shotgun. This bullet does well in two 8x57 Mausers, one in a sporterized original stock with no added bedding, and one in a plastic Ramline with a little epoxy at the recoil lug. I will try Nosler 180 BT next week. Loading Re-17, which really gives a nice 98-102% case fill, good velocity, and good Std.

[243winxb]

How you benchrest the rifle may make the biggest difference. Try holding the forearm with your hand, like if shooting off hand. Then place hand on the bag/rest. No bag in the rear. Check to see if bullet point of impact changes or group size.

[redlightrich]

I apologize for going somewhat off the OP question, but I hear the term bedding often, and it appears that there are many ways to do it. I have read the term "glass bedded" and other terms. I realize this pertains to mounting the action/receiver into the stock, but is there a good resource available that would explain this to an amateur like me?
I once read that an expert, improved his groups considerably by simply removing the barrel band on his Ruger 10/22 carbine ( the band is a decoration I am told).

If the removal of the band can change accuracy, I can only imagine a full stock can alter it even further.

I would appreciate any direction in helping me learn the craft. Maybe this can also help the OP. Sorry, I hope I didn't derail this thread.

Kind regards

Rich

[tobnpr]

Assuming you checked bore condition and crown, you didn't mention it...

I sure wouldn't waste a lot of time and money on ammo trying to chase down a load that shoots. Assuming the receiver bedding job looks good per wpsdlrg, I'd dremel that stuff out in a heartbeat. I've not know it to be SOP to bed barrels on sporterized Mausers...

[243winxb]

When the whole barrel channel is bedded, i would try a pressure point at the very end of the forearm. Install a shimm that puts about 9 lbs up pressure on the barrel. If theres no change in accuracy, only point of bullet impact, i would forget about it.

[Clark]

On bedding I am opinionated, waving my hand about forces, and have no range data to show I am right.

I just finished my 8th 98 Mauser bedding in a row where the only thing that touches is:
1) The bottom of the recoil lug touches the bottom of shallow milled slot in steel. This touching is fastened with the front action screw, and clamps the steel with the top of the bottom metal ring. This attachment makes the stock mass one with the barrel action mass in reaction to rotational recoil from rifling in the bore accelerating bullet spin.
2) The back of the recoil lug touches the back of the same slot. This touching makes the stock mass one with the barrel action mass in reaction to forward acceleration of the projectile and the center of mass of the gas.
3) The rear tang of the receiver is clamped with rear action screw through a 3/8" 1010 steel tube 1.18" long that is epoxied to the stock. This provide the third point to define a plane with two points on the bottom of the recoil lug. This keeps the stock to action connection from pivoting when recoil restraint is off center of the bore, i.e. recoil pad below bore line.

To make sure there are no extra points touching, I smack the barrel and listen for long sustain a of an exponentially decaying sinusoidal audio tone, like a tuning fork. To troubleshoot poor sustain or buzzing, I run a dollar bill between stock and barrelled action.

[F. Guffey]

So I bought a nice looking sporterized Mauser (8mm-06) with an especially good looking stock.

8mm06, I have an 8mm06 chamber reamer; I have 3 Mausers that are chambered to 8mm06. My opinion the stepped barrel is not the perfect barrel for long chambers. I built a 7mm57 Mauser and bedded it from one to the other. It would be difficult to improve on the accuracy; the new owner wants to upgrade the stock to something that matches the accuracy.

I have another rifle that is most accurate; it has the receiver and barrel bedded to the stock, which would be bottom sides and top. Basically it is one piece. The barreled action passes through the stock and stuck with J-B Weld. It is ugly but accurate. It heats up fast and cools slow; the bedded barreled receiver stock is also the recoil lug. I have more money in the scope mount, rings and scope than I have in the rifle.

I built a 270 Winchester on a VZ24 action. I glassed the trigger guard to the stock. I took it to the range with 12 different loads using 12 different head stamps in an attempt to determine what it liked. It liked everything.

F. Guffey

[T. O'Heir]

The term "glass bedded" refers to the fibreglass, um, fibres mixed into the epoxy. Pillar bedding is literally that. Wee 'pillars', usually of Al, that the action sits on in the stock.
The previous owner did a real neat job of doing it incorrectly. Only the receiver out to under the chamber area should be fully bedded. If the rifle likes a floating barrel, not all of 'em do, the rest of the barrel channel is just sealed. No epoxy. Any wood sealer will do. Keeps moisture out of the wood.
If a pressure point is required then it's just a dab an inch or so aft of the end of the forestock. Like wpsdlrg says.
The only thing that is worse is the guy who'd brother-in-law, as I recall, bedded his rifle, barrel channel included, but did not use any release agent. Stock had to be chiseled off.

[Jimro]

I'm still working on loads, but this gun groups very poorly so far. Barrel and rifling look good. It's the original military barrel, and every step is impressed in resin. Before I get out my rasp, is this a likely cause of my poor groups?

No, a full length bedding job is not likely the cause for poor groups.

A full length bedding job was once considered a good thing for custom hunting rifles post WWII. The thin barrels didn't benefit much from free floating, and the goal was to make the rifle shoot tight for three shots (about all you'd ever need for a hunting rifle).

I think you would be better off telling us what you've done for load development before you start messing with the bedding. Realize that back when a lot of these milsurp rifles were getting sported, 2 MOA was considered "sniper grade" by many military forces, and it wasn't until the adoption of the 308 Win that the old 5V target was changed to the moder 10X target. So given that you are dealing with a barrel old enough to qualify for Social Security, I'd make a point of not expecting sub MOA groups without a LOT of load workup.

Jimro

[tangolima]

To me "bedding" means providing a platform to something, say the action of a rifle. It also implies making contact with.

I don't "bed" the barrel if I intend to have a free floating barrel. Instead I seal the channel with bedding compound while maintaining a 0.02" clearance to the barrel, mostly to stiffen the forearm.

I have been bedding the chamber area of the barrel up to few inches in front of the receiver. I was taught to do so, and never have a 2nd thought about it. Now I do. I may try bedding the action only.

BTW, has anybody tried the pure form of pillar bedding? The action sits on the 2 pillars only, and not touching anything else other than whatever the recoil lug rests upon.

-TL

[ligonierbill]

Thank you all for your thoughts. I loaded some Nosler 180 BT this afternoon, and I'll give them a run next week. Of course, there is another option. At the same range session, I took my first shots with a '40 Borsigwalde Mauser that E. R. Shaw rebarreled in .257 Roberts. They blued the action and barrel, too, beautiful job. I put a Richards stock on it (lots of sanding, but not as bad as I've heard) and bedded the receiver ring and recoil lug. I was dialing in the scope and chronographing, but I did put the last 3 in an inch when I quit fooling with it. I could crank this barrel off and send the action to them, and they will do an 8mm-06. At this point I'm not ready for yet another caliber. Thanks again, and I'll report on my success or lack thereof.

[wpsdlrg]

Among the bullets the OP has mentioned, I can comment on two. I have gotten great accuracy from the Sierra 175's.....in fact, this is the most accurate bullet I've tried in my sportered M48. Also, the Nosler 180 BT has been a great performer for me. Of course, every rifle is different. But, I'd say the OP has as good a chance to find success with those two bullets, as any other.

One other thought. "Accuracy" means different things to different people. When I say "great accuracy", as regards my Mauser, I am referring to about 1.5" or a bit smaller, at 100 yards. That is the best I've gotten with that rifle - probably the best it will do.

When I speak of "great accuracy" with other rifles, such as my Stevens .223, (which will do 1/4" at 100 yards)....it is a different thing.

The point being, be careful of the standard you are expecting. Some rifles - many old milsurps included, simply won't do 1 MOA or smaller, or even 1 MOA, for that matter.

[ligonierbill]

OK, I got to the range today and tried the last (hottest) of my 175 Sierras and 160 Barnes. A little better, maybe, but not much. I think I have the solution, though. But first, I tested my 180 Nosler BT over Reloder 17. No better group, but outstanding velocity. Quickload says I'm good, although there is not a lot of published data yet on Re-17. I got 2,883 avg/7 Std with 59 gr of this powder. No overt pressure signs. "Poor man's magnum" indeed.

Now my problem, assuming it's not just a worn out barrel. It doesn't look worn out, but if that turns out to be the case, I will get Shaw to rebarrel in 8mm-06. I'm warming up to this round. I think the cause is not radial expansion, but axial. As I noted at first, the barrel steps are cast in epoxy. The barrel doesn't have to get very hot before the axial expansion will create stress where the barrel step contacts the epoxy step. And it wouldn't take much, considering the steep angle, to move the point of impact. At least one group held within an inch or so horizontally, but "walked" higher. I am going to at least smooth out those steps and try again.

[jmr40]

Most don't full length bed the barrel but I've seen some gunsmiths do it. I bought a couple of 2nd hand rifles over the years that were done that way. If it is done right it is one way to get consistent accuracy. It works best on thinner barrels But most people free float today and that would be my preferred method.

[tangolima]

Originally Posted by ligonierbill

I think the cause is not radial expansion, but axial. As I noted at first, the barrel steps are cast in epoxy. The barrel doesn't have to get very hot before the axial expansion will create stress where the barrel step contacts the epoxy step. And it wouldn't take much, considering the steep angle, to move the point of impact. At least one group held within an inch or so horizontally, but "walked" higher. I am going to at least smooth out those steps and try again.

So does the barrel free float in the channel? It is difficult to see how the radial and axial clearances can be different. Suppose they are different, the steps can be easily moved forward with a dremel bit for more clearance.

If you haven't done so, also check the crown. I tried almost everything under the sun to get my sks to shoot decently, and failed. I recut the crown as a last step before giving up. It made a tremendous improvement.

-TL

[ligonierbill]

If you model a rifle barrel as a right circular cylinder, say 2 cm diameter and 70 cm in length, and assume 1% expansion, it changes diameter 0.2 mm and length 7 mm. Gross example, and I didn't look up the coefficient of thermal expansion for steel, but there will be more absolute dimensional change in length. So I'll take off the steps and see if that helps. The crown looks OK, but that's another possibility. At this point I do think the problem is with the rifle. And, as others have noted, it is an old barrel. It's stamped 1922, and I know from researching my old "family" 1916 Danzig that a lot of Mausers were refurbished and rebarreled in that time frame. So it's likely a lot older than I am.

[mete]

My 2 cents .It is easy to introduce harmful stress during bedding, both in the receiver and barrel !!
My M98 had a stepped barrel originally which was designed for the original military cartridge !! That for accuracy.
The vibrations in a rifle occur from the bullet going down the barrel .But the receiver must be firmly attached to the stock to form a RIGID pair. A fully bedded rifle may be accurate for a specific load . Better is a barrel free to vibrate.In gunsmithing school they suggested bed receiver + 2" of barrel . That certainly worked for me .
A thin ,light weight barrel will vibrate more than a heavy one .Care should be taken to have enough clearance so the barrel vibrations don't touch the forend ! Like my .223 Kimber did .

[tangolima]

The thermal expansion coefficient for steel is 12e-6 m/m*C. For temperature rise of 100 degrees C, mighty hot for a Mauser rifle, the expansion will be 0.12%. Besides the steps are at less than the full length of barrel. I'm not saying it is not important, but 7mm is a bit far fetched.

Now I guess the barrel is not free floating. I have done a few bedding myself. So far there are very few rifles that don't like free floating barrels.

1922 is old, but doesn't mean no good. I have gew 88 (Spandu) that was rebarreled in 1905. Shoots better than 2 MOA with iron sight. Same is my smle that was made in 1917.

-TL

Originally Posted by ligonierbill

If you model a rifle barrel as a right circular cylinder, say 2 cm diameter and 70 cm in length, and assume 1% expansion, it changes diameter 0.2 mm and length 7 mm. Gross example, and I didn't look up the coefficient of thermal expansion for steel, but there will be more absolute dimensional change in length. So I'll take off the steps and see if that helps. The crown looks OK, but that's another possibility. At this point I do think the problem is with the rifle. And, as others have noted, it is an old barrel. It's stamped 1922, and I know from researching my old "family" 1916 Danzig that a lot of Mausers were refurbished and rebarreled in that time frame. So it's likely a lot older than I am.

[ligonierbill]

Mine was a "for instance", but thanks for running an actual calc. Let's say 30 cm to expand 0.1%. That's 0.3 mm, not very much, but if my barrel step is in contact with the epoxy step, which it appears to be, that interference will generate unwanted and variable stress on the barrel. In any case, I will smooth out those steps today.

Regards the loads those barrels were designed for, that's true. However, my old Danzig (and these old eyes) shoots better than this wildcat with warm loads and aperture sights.

[tangolima]

A chamber cast is also a good tool. It will tell you the condition of the leade, the riflings near the chamber, and the groove diameter, etc. At least some of the information is pertenant to accuracy.

-TL