Barrel length in relation to velocity

[Texasgrillchef]

for the purpose of examples only I will refer to 22LR.

I have been doing some research online, and have yet to find anyone that has done any actual studies showing actual results in how barrel length has an effect on velocity.

Obviously the longer barrels of rifles increase FPS over firing the same ammunition in a shorter barrel of a pistol. This is of course due to being able to obtain full powder burns in a longer barrel.

But what differences we would get say from a SBR 12.5” barrel to that of 16.5”, 18.5”, 20”, and say even 22”. At what length would we be getting full powder burns, and now barrel friction starts to have a noticeable impact on maintaining maximum velocity?

I have seen discussions of this in other forums relating to 22LR claiming maximum velocity from either 16.5” or 18.5” and much slower velocities from SBR lengths of 12.5” and 14”, as well as slower velocities from 20” and 22”. Although they did not provide any chronograph data for any barrel length.

I have a Ruger 10/22 Carbine with the 18.5” factory barrel. I ran 100 rounds each of 36 grain browning ammo, and Remingtons 40grain Thunderbolt ammo. Browning’s ammo gave me an average of 1156fps, with 1221fps as the high, and 1053fps as a low.
The thunderbolt ammo from Remington gave me 965fps as a low, 1056fps as the average and 1109fps as the high. All of these speeds are well below the published speeds on the box of both Browning and Remington. Which was not a surprise to me at all.

Which makes me wonder. Hypothetically speaking. If I had the following barrels to test,
Would the speeds be faster or slower then my current 18.5” barrel?
Barrel speed in question, 12.5”, 16.5”, 20” and 22”

My thoughts are that the speeds would be slower in all the barrels except the 16.5” barrel in which speeds would be the same or just slightly a bit higher.

What are your thoughts? Would this same rule apply to other barrel lengths in other calibers? This is a discussion on how barrel length affects velocity, not which barrel length is best or worst, nor is it a discussion if the highest velocity barrel length will or won’t give you the best accuracy.

 

[LoonWulf]

http://www.ballisticsbytheinch.com/

on the .22 I have a 5.5, 10, 18, 20, I can Chrono all those and see.

 

[Texasgrillchef]

http://www.ballisticsbytheinch.com/

on the .22 I have a 5.5, 10, 18, 20, I can Chrono all those and see.

Hey thanks that would be cool, if you do, use the same ammo! Lol I would be interested in seeing the results.

I am going to do some number crunching from the site you gave me. I do see a few issues with their data collection from a scientific POV, but there is enough data to get an overall feel of the trend, it shows obviously shorter lengths like 4” barrels are slower then 18” barrels, but in the scope of things, not really any kind of huge difference such as velocity doubling.

 

[LoonWulf]

yeah maybe weekend after next, I got enough rounds of 3 or 4 different types to get a decent base line for each on all my guns.

 

[fpgt72]

I would think another issue would be ammo.

You would need to run a good sized sample through just to get a good idea on what the ammo does round to round before you move barrel to barrel. You just don't have control over rimfire like you do if you are rolling your own.

I would think if you go to a high quality ammo, you could get by with around 20 for your control group....all from the same lot, and in that control group I would mix up boxes if say the boxes are 50 rounds per.

It would be a very interesting test.

 

[Varminterror]

22LR is a pretty uninteresting cartridge for the “ballistics by the inch” type analysis because of its unique challenges which do not afflict any centerfire rifle cartridge. It’s incredibly sensitive to bore quality and condition (such two barrels of the same make and model can vary by far more than two barrels of different lengths), AND its diminutive case means it’s actually an exceptionally underbore cartridge - running out of progressive pressure in a rather short barrel.

For example: I shoot a Savage Mark II BSEV with a 21” barrel, as well as a Ruger Charger Pistol with a 10” barrel. I regularly shoot these to 325 yards, and despite 11” more barrel in front of the Savage rifle, both average right around 1225fps at the muzzle, and I use the same drop data for both, side by side. 325yrds might not seem terribly far, but it’s still more than 100” of drop, so VERY long for the cartridge.

 

[saiga308]

for the purpose of examples only I will refer to 22LR.

I have been doing some research online, and have yet to find anyone that has done any actual studies showing actual results in how barrel length has an effect on velocity.

.

 

[Texasgrillchef]

I would think another issue would be ammo.

You would need to run a good sized sample through just to get a good idea on what the ammo does round to round before you move barrel to barrel. You just don't have control over rimfire like you do if you are rolling your own.

I would think if you go to a high quality ammo, you could get by with around 20 for your control group....all from the same lot, and in that control group I would mix up boxes if say the boxes are 50 rounds per.

It would be a very interesting test.

Well of the two varieties, the Thunderbolt came out of a bulk box of 500, the Browning came out of a bulk box of 1000. I felt like a 100 round sampling of each was a good sample. You are correct I should try some other ammo as well.

 

[LoonWulf]

I've got enough Federal HV Match, CCI Standards, and Minimags to test 100 rounds of each, think I've got a couple bricks is Aguila standards and HVs also. I can get others if anyone has a specific request.

 

[Texas10mm]

22LR is a pretty uninteresting cartridge for the “ballistics by the inch” type analysis because of its unique challenges which do not afflict any centerfire rifle cartridge. It’s incredibly sensitive to bore quality and condition (such two barrels of the same make and model can vary by far more than two barrels of different lengths), AND its diminutive case means it’s actually an exceptionally underbore cartridge - running out of progressive pressure in a rather short barrel.

For example: I shoot a Savage Mark II BSEV with a 21” barrel, as well as a Ruger Charger Pistol with a 10” barrel. I regularly shoot these to 325 yards, and despite 11” more barrel in front of the Savage rifle, both average right around 1225fps at the muzzle, and I use the same drop data for both, side by side. 325yrds might not seem terribly far, but it’s still more than 100” of drop, so VERY long for the cartridge.

Yep. Right in that 10-14" range is where .22 LR starts to run out of steam.

The ideal test would be to get a Ruger 10/22 barrel that's 24-26" long and a couple cases of ammo. Fire the first string then lop off 1-2" of the barrel. Repeat till the barrel gets short enough to be required to be installed on a Charger and keep going. Or you could just use the Charger through the whole thing.

That way you eliminate the barrel variable.

 

[Spade5]

You could check out ballistics by the inch. They only do handguns from 2 to 20 inches I believe. Probably five or six different commercial rounds.

 

[Varminterror]

Yep. Right in that 10-14" range is where .22 LR starts to run out of steam.

The ideal test would be to get a Ruger 10/22 barrel that's 24-26" long and a couple cases of ammo. Fire the first string then lop off 1-2" of the barrel. Repeat till the barrel gets short enough to be required to be installed on a Charger and keep going. Or you could just use the Charger through the whole thing.

That way you eliminate the barrel variable.

That’s exactly what ballisticsbytheinch.com did - plus they added data from exemplar firearms as much as possible and practical.

 

[Texasgrillchef]

That’s exactly what ballisticsbytheinch.com did - plus they added data from exemplar firearms as much as possible and practical.

They varied the gun from one to one to... so it wasn’t the same 22lr gun that they tested the barrel lengths on. So the data isn’t truly comparable. Ie they didn’t do a 10/22 with various lengths.. they varied the gun from various lengths. So doesn’t give you quite correct true comparaisons.
For a true scientific study, you have to keep all variables the same, and only change one variable throughout the test.

What a previous poster posted in taking a longer barrel and then cutting it down each time, problem of that is you need to clean the barrel after each cutting, and even then you would have “wear and tear” on the rifling. Maybe enough to make a difference in friction, maybe not. Why having new fresh barrels in various lengths to test would make the most sense, along with testing several brands of ammo as well.

Seems from the data I am gathering so far, is that the true differences doesn’t vary drastically unless your comparing a short 4” barrel to that of a 24” barrel. And even then it fluctuates depending on ammo as well.

 

[Varminterror]

@Texasgrillchef - read up on the ballisticsbytheinch.com method.

They used single shot barrels, cutting 1” chunks from each barrel as they went. There ARE varied “real world” gun data tables as well, but the standard table on their page was shot through the same gun, same barrel, cut down in the field with a chop saw, exactly as you’re describing.

 

[Varminterror]

Why having new fresh barrels in various lengths to test would make the most sense

When you buy a few barrels in your life, you’ll notice this absolutely does not make sense. Two barrels, cut on the same drill, will not have identical velocities. Such you might see a 20” barrel shoot slower than a 16” barrel, and an 18” barrel shoot slowest of all.

There’s no feasible means to eliminate all sources of error. For a 22LR, cutting the same barrel is far more valid than having various fresh barrels. For a 243win, almost nothing is valid for statistical satisfaction, as firing wear happens so fast AND barrel-to-barrel variability is great enough, very little can be done to improve the experiment.

So you can repeat what many have now done before you, either compare various barrels of various lengths, or cut down a single barrel, or you can pursue your own experimental design with its own inherent and unavoidable errors. Data is out there though.

 

[taliv]

When you buy a few barrels in your life, you’ll notice this absolutely does not make sense. Two barrels, cut on the same drill, will not have identical velocities. Such you might see a 20” barrel shoot slower than a 16” barrel, and an 18” barrel shoot slowest of all.

or so the internet says, but i've been through a few barrels and that has not been my experience. maybe for factory barrels. and i'm not saying the occasional barrel isn't slightly different, but after break in, all the barrels i've had of a given length shot the same velocity with same load. i haven't seen a difference


btw, good on bbti for testing and posting data, but their actual process does seem to leave a lot to be desired.

 

[Varminterror]

Buying a bunch of air gauged, hand lapped barrels is a little different than buying a bunch of hammer forged or button rifled barrels.

Even among custom tubes, fast and slow tubes exist. The Rock Creek I shot last year was about 100fps slower than any other 24” shooter I compared loads against - and slower than my Bartlein this season.

After all - we’re talking about 22LR here, such we won’t expect those 25-50fps per inch jumps we see with centerfires. Being “close” in velocity between two barrels is different than being “exactly the same.” Within the standard ES of the load? Eh, maybe. Since 22LR ammo is often quite variable, but if we’re talking a couple fps per inch up or down, I readily expect the difference between two 20” barrels to be greater than a barrel cut from 20” to 19”.

 

[jmr40]

Short version: A 22 RF will top out with about 16-18" of barrel. From 18" to about 22" there is generally not a huge difference. I've seen reports of barrels longer than 22" actually shooting slower than shorter barrels.

But this is far from an exact science, the above is just generalities. Individual barrels of the same length can vary considerably with the same ammo. I've not compared 22's that much. But with center fire rifles 25-50 fps difference with equal length barrels is normal. And 100-150 fps difference isn't unheard of. All of my 22" 308's are within 20-30 fps of each other with the same ammo. But I have two 30-06 rifles, both with 22" barrels. One of them is consistently 90-100 fps slower than the other. I have a friend with a 22" 30-06 that runs 130 fps slower than my faster rifle with ammo from the same box.

 

[Skylerbone]

It may be that there are too many variables to eliminate for scientific conclusions to be offered. Different burn rates, powder charges, even drill diameter or bearing surface, slug diameter, bullet composition, bullet design, and of course where within the barrel the smallest diameter lies.

I’m not so accuracy obsessed as to concern myself with measuring out $5 Marlin barrels where my only concern lies in whether it’s a “good shooter”. It’s cob rough in there, no hand lapping, no purposely chosen narrowing at the crown.

Without irons to benefit from sight radius I’d say handiest practical length for purpose will win out for most and most consistently accurate maker will collect money from the rest. Just the opinion of a duffer though.

 

[Texasgrillchef]

It may be that there are too many variables to eliminate for scientific conclusions to be offered. Different burn rates, powder charges, even drill diameter or bearing surface, slug diameter, bullet composition, bullet design, and of course where within the barrel the smallest diameter lies.

I’m not so accuracy obsessed as to concern myself with measuring out $5 Marlin barrels where my only concern lies in whether it’s a “good shooter”. It’s cob rough in there, no hand lapping, no purposely chosen narrowing at the crown.

Without irons to benefit from sight radius I’d say handiest practical length for purpose will win out for most and most consistently accurate maker will collect money from the rest. Just the opinion of a duffer though.

I fully agree, there are way to many variables to truly do anything in a pure statistical scientific data acquisition model.

I also agree that if one isn’t using irons for sight radius, the length of barrel should be a length that is practical for use that is needed of the weapon. There are obvious reasons why we find various barrel lengths available for various guns and calibers. Such as what I have found in 22lr for the 10/22 being 12.5”, 14.5”, 16.5” 18.5”, 20”, 22” and 24”. Of which in rifle configuration requires a NFA tax stamp to legally have on a rifle. There are even shorter ones available for 10/22 pistols as well.

It is also interesting to note that the fastest barrel may or may not be the most accurate barrel as well.

Personally, while others may disagree. A speed difference of 100-150fps isn’t a significant difference to me to really make that much difference for the purposes that I shoot my weapon. Of course this difference in speed would be significant if the difference was on the border of the sound barrier and we wanted our projectile speed to be consistently above or below the supersonic/subsonic range. Even simple weather itself can even vary the speed of sound by that much too. In which case barrel selection and ammo selection becomes even more important in keeping a projectile subsonic/supersonic.

1100fps Ammo may or may not be subsonic depending on weather that day and barrel length.

 

[fpgt72]

I might have missed this but it might be cool to see the difference between say micro groove and "regular" type rifling over the same length of barrel.

Correct me if I am wrong, but I thought the micro groove was to not "bite" into the bullet as much so slow it down as much or distort it as much.....going to have to read up on the why's people think microgorve is better.

Does any 22 use the poly type rifling (I ain't even trying to spell dat word) like glock and early CZ's used?.....wonder what that would do.

This would be a fun test for someone with the equipment to really do it correctly.