How do Rifle Stock Designs Affect accuracy?

[Jamie Young]

I've often wondered why the M1 Garand and the Enfield Rifles were shrouded with so much wood. Why is that? Doesn't a rifle cool down faster when it is exposed and not contained?


I've read a few posts lately that mentioned Glass Bedding a rifle barrel. What is that?

 

[Jamie Young]

No I haven't gotten the targets yet. I'll PM or email you as soon as I get them.

 

[bsmart]

Sodapop, DonQatU has given you the basics in his explanation. The old Lee Enfield .303's and other full wood guns were produced like that to protect the user in time of combat when the barrels got red hot. These days, a sporting shooter wants the absolute best out of his/her gun. A timber stock can vary the accuracy of any weapon that has one. If you float your barrel, the stock does not come into contact with the barrel and affect the accuracy. Some people bed their guns, using two pack epoxy or fibreglass. Being synthetic it does not swell and contract like timber does. That is the main advantage of synthetic stocks.

 

[Art Eatman]

sodapop, the reason that contact between the forearm and the barrel can affect accuracy is that the steel, as it heats up, expands at a different rate than the wood. This differential means a change in pressure at any contact point between wood and steel.

A barrel behaves as a spring when the gun is fired. So, a change in the vibrations means a change in the bullet's path. Miniscule at the muzzle; more, out at 100+ yards.

As to the military wood, think how hot a barrel gets after 20 or 30 very fast rounds, even through a bolt-action--much less a semi-auto or selective-fire critter.

, Art

 

[Ledbetter]

Tuning fork

Greetings,

Think of the barrel as one tine of a tuning fork. You want it to vibrate exactly the same way (same pitch) each time. To accomplish this, the action should be secured into the stock to eliminate any variations from shot to shot that might affect the vibration of the barrel. This eliminates (theoretically) shot to shot variation caused by minute repositioning or loosening of the action in the stock after each shot. Shot to shot variation may thereafter be attributed to the shooter or the ammo, if the action is well bedded and the barrel is in good condition.

Some folks also bed the first couple of inches of the barrel, free-floating the remainder. My favorite bedding material is Marine Tex boat hull repair.

Regards,

Ledbetter

 

[Jamie Young]

How do you dermine if a Barrel Whips?

I understand the concept, but would a gun return to Zero after this was occuring?

 

[Art Eatman]

Sure, sodapop; in micro-seconds. The whole deal is that there is consistency in the vibrations. If there is no outside force acting against the barrel (out in front of the receiver), there is no differential stress as the barrel heats. Therefore, consistency.

Now, some barrels can have internal stresses in the steel. Inadequate heat-treat and all that sort of industrial or manufacturing problem. That has to do with the quality of the barrel itself, not how it's mounted in the stock. A change in these internal stresses as a barrel heats up can affect the consistency of the aforementioned vibrations.

Simple, ain't it?

, Art

 

[Jamie Young]

. That has to do with the quality of the barrel itself, not how it's mounted in the s

Thats what I wanted to know. So how does putting extra weight on a Muzzle change Barrel whip?

Does it just delay the inevitable? I don't know if putting a Flash Suppressor made a difference on My MIni 14 or not.

 

[sleeping dog]

Maybe the brits have strange ideas about firearms. My Enfield (Ishapore 2A1) had a spring loaded thing under the front of the barrel pushing up on the barrel. Also, some of the old writings about Enfields described packing some channels in the forestock so they would hold onto the barrel better. As I remember, there were two or three channels cut across the insice of the forestock for that purpose.

SodaPop, isn't a flash suppressor an "evil feature" that can't be added?

Regards.

 

[Jamie Young]

There are plenty of Legal ones out there. The Coolest ones got banned

 

[Cheapo]

The barrel will always point to the same spot when at rest between shots, if it is properly mounted in the action and the stock is not giving it variable tenstion.

The problem/solution comes in the barrel vibrations as the bullet is zooming towards the muzzle. A curious and fortunate thing happens with .303 Enfields, for example--slower rounds exit the muzzle when it's vibrating more "up" than do the faster rounds. In their world of 2-3 MOA, they found that accuracy actually improved a bit somewhere beyond 600 yards. Turns out the trajectories of the faster and slower rounds were converging at that magical distance, whatever it was.

The Browning BOSS improves accuracy by letting you adjust the barrel vibrations so they are consistent for each shot, _for the moment the bullet leaves the muzzle._

Although you would expect the barrel to vibrate exactly the same way for every shot, all the other variables (including those shot-to-shot velocity and pressure differences, maybe?) leave us with some LOADS spitting the bullet out when the barrel is in the middle of either whipping up or down or sideways or whatever.

Bedding becomes very important if the action is able to SHIFT tiny bits in the stock during bullet travel. All the repeatability of your barrel and sights/scope and all that goes out the window if the entire action is being "bumped" around between primer ignition and bullet exit.

Hope this helps...

 

[Art Eatman]

SodaPop, keep in mind some of the strange goings on with barrels that Cheapo talked about:

"So how does putting extra weight on a Muzzle change Barrel whip?" The quick answer is that it affects the vibrations of that spring or tuning fork. Maybe for this it helps more to consider it as a tuning fork (Which by strict Physics is a spring.) To get good rsults, it's less how much weight than it is "where". If it's in the right place, the behavior becomes uniform from shot to shot.

Think of the "sweet spot" spoken of about tennis rackets or golf clubs. That's what you're hunting for, whether it's by use of a Boss or by a weight. According to Gale McMillan, a perfect barrel would not need any help. Glass bed the action; free float the barrel. It's the not-perfect barrels that most of us have to deal with...

There will be some combination of "meddling" which will give the most consistent vibration of a barrel, which will give the best results for group size.

Art