rifle barrel length


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Jim_100
December 5, 2008, 08:34 PM
Are rifle barrels for units like your typical bolt action hunting rifle the exact length that when the bullet leaves the muzzle the gas is just finishing expanding? Does this make sense?
Would you get more velocity if the barrel was the impractical length of say 9feet?

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gvnwst
December 5, 2008, 08:54 PM
No to the first thing, that is ahy muzzle blast exists. For a barrel to be so long that the gas is no longer expanding, the bullet would simply stop because of the friction, there would be no pressure to push it out anymore. Some people have tried super quiet .308 loads and actually gotten the bullet stuck in the barrel! not enough pressure to get it out.

As for the best barrel length, if it doens't matter, i don't know for most guns. On .22s for instance, though, the ompimal length is somewhere around 15"-16", a really long (20"+) tube actually starts to slow the bullet.

Shawnee
December 5, 2008, 09:22 PM
The subject of barrel length has been discussed (and cussed) back and forth since Forever. Almost always the concern is about how much velocity is gained or lost by changing the barrel length.

Most of the modern (read smokeless powder) cartridges perform very well with barrels ranging anywhere from 22" to 26". A couple (the .25/06 is one) seem to benefit from barrels of 24" or more. But, for the most part, the terminal performance pretty much stays in the satisfactory zone with all the common barrel lengths.

However....

I've always thought it would be a great idea if research was done (and published) on the decibels of muzzle blast each caliber produces in all the different barrel lengths.

A hunter whose mode of hunting entails a lot of walking - and thus a lot of carrying his gun, should really choose a light, short highly-maneuverable rifle. In doing so, though, he is increasing the blast (and recoil) - and so should seriously consider buy his rifle in a caliber with comparatively modest muzzle blast and recoil. If you've ever touched off a .308 with a 18" barrel you know it is decidedly louder than one with a 24" barrel. And if you've ever fired the old Remington 600 in .350 Rem. Mag., you definitely understand the problem.:what:

The hunter who spends most of his hunting hours sitting in a blind or stand and not much time lugging his smokepole can afford to use a heavier gun with a longer (blast-reducing) barrel and can choose a "heavier" caliber, if desired, with less concern about muzzle blast and recoil because he can simply buy a heavier rifle with a longer barrel. I know more than a few stand hunters who use heavey-barreled, larger caliber rifles for deer with deadly effect.

Anyway, I think it would be very interesting to see the loudness differences between calibers and between barrel lengths within each caliber.

:cool:

marsche
December 5, 2008, 10:44 PM
I think I know what you are trying to say, Jim, and it is an interesting question. I think you are referring to the length of a barrel for a particular caliber, bullet, and load to achieve the maximum foot per second at the muzzle. In other words, how long does the barrel have to be before the bullet no longer accelerates in the barrel? I read an article that said the optimal length for a 22 rim-fire barrel is 20 inches. I don’t think optimal, in this instance, means the bullet will cease to accelerate at 20 inches. I think optimal means when the FPS second gain in velocity due to another inch of barrel, is not significant enough to justify a longer barrel.

Along the same lines, I have a 6.5-284 Savage that has a 30 inch barrel. The idea of the long barrel is to squeeze some extra velocity out of a particular bullet and powder charge. During my quest for the ‘1,000 yard dream machine’ I read a lot of articles on long range shooting. Some of those articles talked about the same subject. However, their question was how much will I gain in FPS if I add an extra inch of barrel? After a lot of reading, my conclusion is there is no ‘one size fits all’ answer. Back to your question, I never heard anyone ask how long does the barrel have to be before the bullet stops accelerating? I feel sure the barrel length where one additional inch of barrel will no longer yield one more foot per second of velocity is different for every caliber, bullet, and load combination. I guess the only way to find the answer to your question is to build the 9 foot barrel that you talked about, shoot it over a chronograph, and trim one inch from the barrel after each shot. When you notice a rise in velocity you found the maximum length of a barrel for that combination. If you never notice a rise in velocity, then the barrel was not long enough in the beginning. Get a longer barrel and start over.

interlock
December 5, 2008, 11:02 PM
I think it is something to be aware of. I use a remmy model 7 in 7mm08. it has a really short barrel. so i try to load for it in a way that uses faster burning powder. I know that with 145 gr bullets over slow reloader 19 i get a huge muzzle flash and the velocity i believe is highly effected by the shorter barrel. so i use 120 gr bullets and h4895. this is a faster powder. I get much less blast and i believe a better efficiency.

A 22- 24 inch barrel will get good results with most powders.

interlock

moooose102
December 6, 2008, 07:38 AM
most of the velocity of a rifle cartrdge is created in the first 20" or so. the large cased magnums can always use a longer barrel because of the sheer volume of slow burning powder. some need as much as 26" to get the most from the cartridge, and sometimes, might be able to use a little more. but, you have to think about manuverability and balance also. what good is a rifle if you can not change directions with it. for an experiment,go buy a peice of, say 1/2" steel rod of about 2 feet in length., protect your rifle barrel by wraping it with tape, and tape on that peice of steel rod, making it as long as pratical. then try to manuver the gun. you will instantly notice the additional weight, how it affects the balance of the rifle, and how much longer it is. a long barrel is nice to get the most out of your cartridge, but it is not so nice in the woods. if you ONLY shot bench rest competitions with it, then a long barrel would be fine. but for aveage firearm use, there has to be a practical limit.

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