Question for the rimfire barrel length gurus

Grouse Man

Grouse Man

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It seems that the optimum barrel length for .22LR is about 18" or so for maximum velocity. I know that target rifles have barrel lengths of much longer - 26" sometimes. There is a great benefit for the sighting accuracy over a longer distance, and some other optical benefits I understand.

But are there any other ballistic benefits to longer barrels? Does muzzle velocity become more consistant? Do barrel harmonics become less of an issue? Anything else?
 
some time ago there was an article in a gun magazine where they began with a 26'' barrel,and kept cutting it back 2'' at a time checking velocity-and the conclusion was a 16'' barrel produced the peak velocity for a 22 LR,-longer barrels had lower velocity-due to increased friction.I'm not sure what the optimum length was for a 22 magnum though.
 
ratherbefishin said:
some time ago there was an article in a gun magazine where they began with a 26'' barrel,and kept cutting it back 2'' at a time checking velocity-and the conclusion was a 16'' barrel produced the peak velocity for a 22 LR,-longer barrels had lower velocity-due to increased friction.I'm not sure what the optimum length was for a 22 magnum though.
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Uh, I kinda just said I knew that already. :rolleyes:

Thanks anyway. :D
 
If not using irons, I don't see any benefit of a longer barrel. Perhaps it makes the gun heavier/steadier on the bags? I suppose if you were shooting a particular ammo that was just hanging around the speed of sound with the short barrel, you could get some wobbling as it falls from above to below before it reaches the target. With the longer barrel, the velocity might stay below from the muzzle.....?
 
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I searched it over a RFC. The genral consensus is that a standard or high velocity .22lr round peaks at 14-16''. Hyper velocity is past that.

So the optimum length for velocity is somewhere between 14-20'' depending on the cartridge.

If I were to guess as to why there are barrels longer than this I'd say it has something to do with harmonics.

All I know for sure is my 16'' and 18'' gm barrels are super accurate with the right loads.
 
Longer barrel may give your prefered ballance by putting weight forward, in games such as huntier silhouette, where a short, heavy barrel will put you in another classification.

I would think the longer the bullet is in the barrel, the more time it has to be sent off coarse by movement of the rifle after the trigger release.
 
I have rimfires with 17", 18", 19", 20" 22" 24", and 27" barrels. I have graphed one lot of 22 Standard velocity ammo out of them all on the same day. While the shorter barrels do show a bit higher average velocity, the difference is sure not any substantial numbers. For example, the difference between the 17" and the 27" averaged only 24 fps. A better test would involve one barrel, starting at full length and gradually cutting it back, graphing one lot of ammo at each length. But this give some idea what is happenning anyway. Regards, Eagleye.
 
I think the main advantage to the longer barrels, would be, as mentioned the sight radius for using with sights. Much easier using sights on a 28" barrel than it is on an 18" barrel.

As also mentioned, though, the longer the barrel the more it can be set off tract after fired when it is still exiting the barrel. Now this may not make a whole lot of difference in benchrest where the gun (should) recoil strait back and freely but when shooting standing or another position similar follow though would be critical so that you are not disterbing the bullet when it is exiting the barrel.

Another thing to think about would be harmonics. A shorter barrel tends to vibrate less than that of a heavier barrel of equal thickness. Generally this would be a good thing unless a tuner is used (and again, a tuner will have great effects on a skinnier longer barrel than a shorter fattter barrel).

Jordan
 
cz452shooter said:
Another thing to think about would be harmonics. A shorter barrel tends to vibrate less than that of a heavier barrel of equal thickness. Generally this would be a good thing unless a tuner is used (and again, a tuner will have great effects on a skinnier longer barrel than a shorter fattter barrel).
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A lot of the harmonics argument also seems to revolve around o/a barrel design, not just length. A small point, but worth adding.

The 16-inch barrel definitely induces more bark, but where I shoot the general concensus is that the firearms that sport the 16-inch barrel (as well as the "carbine" name, more often than not) are often less accurate than their longer-barrelled bretheren.
 
Eagleye, can you make any comment on the velocity variations of those different barrel lengths? What I'm curious about is if a 16" barrel records m.v. at 1,300 +/- 40 fps, but a 26" barrel shows muzz. vel. of 1,100 +/- 10 fps. I'm theorizing that the longer barrel and greater volume behind the bullet inside the barrel may reduce the variation in muzzle velocities. Just a thought.
 
Velocity ain't everything, especially when you're dealing with a heeled bullet at sub to trans-sonic speeds. In fact, too much of a good thing actually spreads groups...

But to the matter at hand...

My experience has been that the longer sporter weight barrels shoot tighter than the shorter ones. I think a longer bbl. gives the bullet more stabilization- more twist for the bullet to travel through as being the reason. My small game targets don't usually miss the double digits in velocity- they can only be dead a certain amount;) Is it a coincidence that velocity gain falls off at the 16" when the LR twist is 1-16"? I don't think so... This of course is just my personal experience and observation- YMMV, as usual..

Edit: I should mention that those barrels are scoped, and groups measured on paper...

Regards,

Doc Sharptail
 
1992 Gun Digest had a good chapter on 22's, including cutting back barrels one inch at a time. The biggest effect on accuracy was the chambering.
 
Rifling spins the bullet according to the amount of twist the rifling is made with. I don't see how the amount of time in the rifling is related at all to how "good" it is at spinning the bullet. There are way more variables in your comparison of barrel length versus accuracy than simply the amount of time the bullet was under the influence of the rifling. There are all sorts of reasons that could explain why you've had better experience with longer barrels, but the amount of time the bullet is under the influence of the rifling isn't likely to be anywhere near the top of that list. The rifling does its specific job very quickly. And its specific job is simply to spin the bullet. Nothing more, nothing less. If you took a rifle with a very long barrel on it, and cut 1" off at a time and did accuracy tests at every length you would very likely see wildly varying results. If barrel length was the only variable, in other words the crown was perfect every time, etc, you would see accuracy change at every length. But this wouldn't be due to the amount of time the bullet's in the rifling. This would be due mostly to the fact that the barrel is vibrating differently at each length. You'd be changing where the vibration node is each time you cut another inch off. And at some point you might luck out and get that node right at the muzzle, and it would shoot crazy small groups. (That's exactly what the benchrest guys want to do with their tuners, force the node out to the muzzle.) But it is very safe to say that the amount of time in the rifling would be the last thing affecting accuracy.

And, yes, it is just a coincidence between the 1:16" twist ratio and the 16" of barrel needed to get the most out of the average standard velocity round. I don't see how anyone could even begin to relate the two. Simply because they both contain the number 16? Any given powder has a given amount that it will expand when burning. As it continues to expand, it continues to accelerate the bullet. When the force of that expansion begins to be overcome by the force of friction between the bullet and the bore is dictated by the characteristics of that powder, the bore diameter, and the characteristics of the bullet and bore rubbing against each other. This has nothing to do with the amount of spin that bullet needs to be stable in flight. And the twist ratio is determined by that stabilization need. It's unrelated to powder burn/expansion rates.
Doc Sharptail said:
Velocity ain't everything, especially when you're dealing with a heeled bullet at sub to trans-sonic speeds. In fact, too much of a good thing actually spreads groups...

But to the matter at hand...

My experience has been that the longer sporter weight barrels shoot tighter than the shorter ones. I think a longer bbl. gives the bullet more stabilization- more twist for the bullet to travel through as being the reason. My small game targets don't usually miss the double digits in velocity- they can only be dead a certain amount;) Is it a coincidence that velocity gain falls off at the 16" when the LR twist is 1-16"? I don't think so... This of course is just my personal experience and observation- YMMV, as usual..

Edit: I should mention that those barrels are scoped, and groups measured on paper...

Regards,

Doc Sharptail
Click to expand...
 
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