Rifle extension

[fknipfer]

I'm asking a dumb question so nobody get mad, I just have this thought and I will ask you guys about it. Can a guy make and 4 or 5" extension with very tight tolerances and mounted well so no movement can occur, with a hole of say .320 vs a rifle hole of .308. If this is added would this increase his FPS of the rifle say from a 20" to a 24". I know it wouldn't be a full increase of fps on the bullet but I believe he would get some.
I'm not going to do this but just am curious and wonder if someone has tried it before and has some data.

fknipfer

[Ben_Rumson]

My guess is things like that would prolly do more harm than good.. You wouldn't want the bullet bumping into anything on it's way out...

[Pete44ru]

[Can a guy make and 4 or 5" extension with very tight tolerances and mounted well so no movement can occur, with a hole of say .320 vs a rifle hole of .308. If this is added would this increase his FPS of the rifle say from a 20" to a 24"]

In short: no.

The rest of the story:

All that's being done, in reality, is creating a recessed muzzle/crown - just deeper than usual.

As soon as the bullet base clears the internal crown, the propellant gasses will blow by the projectile (bullet), since they travel faster, and hopefuly not bounce around, negatively effecting the bullet's flight/accuracy.

BTW - What you've described is a common way, via welding, to make a short barreled rifle (a no-no under Federal Law) legal - aka, a permanent barrel extension.

.

[Rusty]

IMHO someone would class it as a suppressor and you'd be in big trouble.

[Rimfire McNutjob]

+1 to what Pete44ru said.

[fknipfer]

The Russian M44 Mosin Nagant has the barrel that is 18.5" long and they turn the barrel back and press a steel outer barrel on it that makes the rifle 21.5 and 22" long. They then add sights and a bayonet on the barrel. The piece is soldered, pressed and pinned. But the 18.5" barrel shoots thru 2.5" of a larger hole. This is a case of a combat rifle doing exactly what I have thought about. It is a very heavy duty rifle used for combat so if they do that so I still think it can be done successfully. It has to increase the ballistics a little bit but the 2.5" maybe so minor maybe not.


fknipfer

[Rimfire McNutjob]

It is a very heavy duty rifle used for combat so if they do that so I still think it can be done successfully. It has to increase the ballistics a little bit but the 2.5" maybe so minor maybe not.

There's no telling what they were thinking back then, but I surmise that it will not improve ballistics in the least. I think that it might adversely affect accuracy as well as you've got turbulent gases blowing by the bullet and potentially upsetting it to some degree. If it were at all beneficial in the eyes of modern firearms manufacturers, you'd probably see it around now and again. Let's face it, the Mosin Nagant is not exactly a recent design.

[AJMD429]

Any increase in velocity would be offset by yaw introduced as the propellant gasses passed the bullet, which in turn would lower the effective ballistic coefficient, and of course, the accuracy.

The incremental cost (i.e. 'per inch') of rifling a longer barrel would favor just doing that, getting a solid increase in velocity, and no destabilization.

The only reasons I can think of to do the 'unrifled' part would be:

• to satisfy some ATF regulation
  for a built-in suppressor (would require holes and baffles and all that, plus a 'tax stamp')
  for crown protection

Since the main reason to protect the 'crown' is to facilitate accuracy, you want a protective cage or guard of some sort, but more like a 'birdcage' flash suppressor on an AR-15, vs. a 'barely-larger-than-rifling' tube, as the 'birdcage' or similar device allows more rapid dissipation of pressure and less negative effect on accuracy.

[Rimfire McNutjob]

It also will increase the sight radius if the front sight is mounted on the extension. However, one might also just move the rear sight back a bit to accomplish the same.

[fknipfer]

Thanks a lot guy for your answers and the food for thought. I don't know why the Russians did what the did, but the old Mosin Nagant is still around and in use by some countries. Probably the design is over 100yrs old.

fknipfer

[adirondakjack]

I suspect they did it because they made up the barrels and tried to get the gun "bought" on a contract, and somebody said "we want XX length barrel" so they cluged together something long enough to meet the contract specs.

[firefuzz]

We used to call those a "bloop tube" on .22 target rifles. Didn't add any velocity, just weight and helped stability.

Rob

[Hobie]

The Russian M44 Mosin Nagant has the barrel that is 18.5" long and they turn the barrel back and press a steel outer barrel on it that makes the rifle 21.5 and 22" long. They then add sights and a bayonet on the barrel. The piece is soldered, pressed and pinned. But the 18.5" barrel shoots thru 2.5" of a larger hole. This is a case of a combat rifle doing exactly what I have thought about. It is a very heavy duty rifle used for combat so if they do that so I still think it can be done successfully. It has to increase the ballistics a little bit but the 2.5" maybe so minor maybe not.


fknipfer

WHY do you think it improves the ballistics? Let's not confuse things. The 1891 action is over 100 years old but the M44 Carbine isn't. Further, I have not ever read nor have I been able to find a reference to such barrel construction for the M44 Carbine. What is your source on this? I think that such machining isn't in keeping with the Russian and Soviet KISS principle. One thing they do do when the muzzle is worn from cleaning or other soldierly activities is to counterbore the muzzle to remove the imperfections. This can give an appearance of such as you describe.

[Malamute]

I don't think it can possibly raise velocity, that comes from powder combustion effiency, IE, under pressure. A section of oversize bored barrel extension isnt going to give a tight bullet seal and cause the powder to continue to increase the push on the bullet. It's somewhat like the gap on a revolver. Take the same length of unvented barrel/chamber with the same cartridge, and the velocity will be higher than a vented one.

There was a guy in the 1860's that built a prototype revolver with a vented barrel (longitudinal vents along the barrel, to rid the bullet of that annoying powder smoke and blast at it went down the barrel). His theory was that the initial "blast" of igniting the charge was what really gave the bullet it's full velocity. Needless to say, his theory didn't work out. His velocity/power levels were lower than "regular" guns.

If well done, an extension wouldnt neccesarily cause accuracy trouble. Many of the variety of muzzle brakes in existence are not evenly ported, and some seem to improve accuracy to a degree in some instances. It just doesnt seem worth the effort to do well tho. A standard recessed crown does a fairly good job of protecting the end of the rifling, so that angle wouldnt be a good reason to go to the trouble. Recrowning a couple times in the life of the barrel would likely be much less effort if you were hard enough on your guns to need it. I'm pretty dang hard on guns, and havent had to have anything recrowned so far in 30-some years of steady use, other than an old 94 carbine that had had about 50 years of serious abuse before I aquired it. Still, it shot about 4"-4 1/2" groups before recrowning, about 2 1/2"-3" after.


In the bigger picture, if you want higher velocity, it would be simpler to rebarrel with a longer barrel. The difference in a few inches of good barrel still isn't going to be earthshaking, or give you any dramatic increase in range. Handloading for a specific use may be much more productive, and you'll likely see an improvement in accuracy, which means more than velocity for about any use.