223 Barrel Length v.s. Velocity Test

dreadpirate · Jan 18, 2015

Don't know if anyone has ever posted this - but a guy took a 26" varmint rifle and using a powered cold saw, measured velocity and cut off chunks of barrel. See link below. He saw something like a 22 fps loss per inch with 55 grn ammo. [EDIT - they also fired heavier bullets]

http://rifleshooter.com/2014/04/223...s-chop-box-and-his-friends-rifle/#prettyPhoto

Overboost44 · Jan 19, 2015

Thanks for that article. Good stuff.

shooter682 · Jan 19, 2015

It is good reading if you are concerned with overall length consider a bull-pup such as the Tavor, Kel Tec RFB, or I would say Styer AUG except it is banned by name here in this Socialist state.

fabsroman · Jan 19, 2015

Kind of incredible that 26" on a .223 makes a velocity difference, but what I have been reading is that 10" on a .300 AAC BLK gets maximum velocity out of that cartridge. Probably has to do with the volume of the boare/barrel with all the gas being used up in the first 10" of a .30 barrel versus it taking 26" to use all the gas in a .22 barrel. Maybe tomorrow I'll do the volume calculation for a 10" .30 cylinder and compare it to the volume of a 26" .22 cylinder. Wonder what that would end up being.

ericoak · Jan 20, 2015

fabsroman said:
Kind of incredible that 26" on a .223 makes a velocity difference, but what I have been reading is that 10" on a .300 AAC BLK gets maximum velocity out of that cartridge. Probably has to do with the volume of the boare/barrel with all the gas being used up in the first 10" of a .30 barrel versus it taking 26" to use all the gas in a .22 barrel. Maybe tomorrow I'll do the volume calculation for a 10" .30 cylinder and compare it to the volume of a 26" .22 cylinder. Wonder what that would end up being.

Should also depend on other factors including bullet weight.

Boom Boom · Jan 20, 2015

Velocity is only part of the equation. Accuracy of the shooter at each barrel length should be factored in. I've seen more than a few comparisons over the years for the AR-15, using barrels with identical specs except for length, typically 16", 18", and 20". The results can be non-intuitive, where a shooter very experienced with a longer barrel might do best with a 16" barrel, despite repeated efforts to prove otherwise.

Magnumite · Jan 20, 2015

Could also be the individual barrel or barrel profile. Shorter barrels tend to 'whip' less also. Life time of learning for sure.

shaddydan · Jan 20, 2015

Interesting, what about powder differences?

sgt23preston · Jan 20, 2015

Boom Boom said:
Velocity is only part of the equation. Accuracy of the shooter at each barrel length should be factored in. I've seen more than a few comparisons over the years for the AR-15, using barrels with identical specs except for length, typically 16", 18", and 20". The results can be non-intuitive, where a shooter very experienced with a longer barrel might do best with a 16" barrel, despite repeated efforts to prove otherwise.

My experience has shown me that I personally shoot more accurately with a 20" barrel of any caliber than I do with 16" barrels...

And I'm an experienced shooter who started shooting an M1 in the USMC in 1961...

However I am unwilling to lug around "long" rifles with 22" or 24" barrels and all my rifles have an overall length of about 42" = pretty comfortable in the woods...

fabsroman · Jan 20, 2015

ericoak said:
Should also depend on other factors including bullet weight.

.22 barrel 26"=36.24 in3
.30 barrel 10"=19.42 in3

Thanks for those numbers. I think the powder charges are about the same in volume for a .223 case and a .300 BLK case, maybe just slightly less for a .300 BLK since a .223 case needs to be cut down slightly to make .300 BLK. I have not worked up a .300 BLK load yet, so not completely sure about it.

Just hard to believe that a .223 needs almost double the amount of barrel volume to reach maximum velocity when compared to a .300 BLK. I'd love to see this sort of test on a .300 BLK.

erwos · Jan 20, 2015

My understanding is that there's not a lot of room for powder in a .300AAC case (especially with the heavy/long bullets), and therefore it requires faster-burning powder to generate the pressures it needs. Faster-burning = less barrel needed for full burn.

You've also got to remember that .300AAC has significantly less energy than 5.56x45 with light supersonics, and has energy roughly comparable to pistol calibers with heavy subsonics. This is why I've always been loathe to go into .300AAC - it doesn't really seem to do anything I can't already do with guns in my collection.

Boom Boom · Jan 20, 2015

sgt23preston said:
My experience has shown me that I personally shoot more accurately with a 20" barrel of any caliber than I do with 16" barrels...

And I'm an experienced shooter who started shooting an M1 in the USMC in 1961...

It's a person-to-person thing. Some guys who shoot competitively and put tens of thousands of rounds downrange per year begrudgingly try a good 16" barrel and consistently out-shoot their 20" barrels at 100 and 300 yards. We're talking quality barrels with a nice scope, not to be confused with the typical bad comparison of a pedestrian 16" barrel against a spendy 20" match barrel.

Bluemax · Jan 20, 2015

5.56 velocity info

You should find this interesting.

stu929 · Jan 20, 2015

erwos said:
My understanding is that there's not a lot of room for powder in a .300AAC case (especially with the heavy/long bullets), and therefore it requires faster-burning powder to generate the pressures it needs. Faster-burning = less barrel needed for full burn.

You've also got to remember that .300AAC has significantly less energy than 5.56x45 with light supersonics, and has energy roughly comparable to pistol calibers with heavy subsonics. This is why I've always been loathe to go into .300AAC - it doesn't really seem to do anything I can't already do with guns in my collection.

Blackout has more energy than a 5.56 round with supersonic rounds where are you getting this? 223/556 struggles to make 1200 ft/lbs needed for deer i have seen a handful of loads for blk that are around of over 1400 ft/lbs. Is it a huge difference no but it certainly isnt less energy.

rob · Jan 20, 2015

Why is no one talking about gas tube length in this context.

A rifle length gas system gives the most time/barrel travel before the loss of gas pressure and a carbine length gas system give the least time. I would think this would be a major factor in bullet velocity.

Rob

BUFF7MM · Jan 20, 2015

rob said:
Why is no one talking about gas tube length in this context.

A rifle length gas system gives the most time/barrel travel before the loss of gas pressure and a carbine length gas system give the least time. I would think this would be a major factor in bullet velocity.

Rob

Actually pistol length is the shortest, but I know where you're coming from.. :thumbsup:

Streetgang · Jan 20, 2015

rob said:
Why is no one talking about gas tube length in this context.

A rifle length gas system gives the most time/barrel travel before the loss of gas pressure and a carbine length gas system give the least time. I would think this would be a major factor in bullet velocity.

Rob

In the article the author used a Remington 700. No gas tube in that case. I'm sure that was chosen to eliminate as many variables as possible.

erwos · Jan 20, 2015

stu929 said:
Blackout has more energy than a 5.56 round with supersonic rounds where are you getting this? 223/556 struggles to make 1200 ft/lbs needed for deer i have seen a handful of loads for blk that are around of over 1400 ft/lbs. Is it a huge difference no but it certainly isnt less energy.

M193 is 1250ft-lbs of energy.
M855 is 1325ft-lbs of energy.
Mk318 Mod0 is 1280ft-lbs of energy.

That's hardly "struggling". And if you go for some of the better 5.56x45 loads, 1425 ft-lbs is not completely out of the question (Hornady Superperformance). But, you're right, I shouldn't have said .300AAC is worse, it's comparable at the muzzle.

OrbitalEllipses · Jan 20, 2015

erwos said:
M193 is 1250ft-lbs of energy.
M855 is 1325ft-lbs of energy.
Mk318 Mod0 is 1280ft-lbs of energy.

That's hardly "struggling". And if you go for some of the better 5.56x45 loads, 1425 ft-lbs is not completely out of the question (Hornady Superperformance). But, you're right, I shouldn't have said .300AAC is worse, it's comparable at the muzzle.

You're absolutely correct on your assessment of the .300AAC subsonic loadings though. No better terminal performance than a big bore pistol - actually almost identical to a .45ACP, though I concede numbers don't tell everything. I haven't seen any hard data on wound channels, etc. though I imagine it's not too different than a pistol cartridge...rifles ultimately wound more spectacularly due to their velocity and .300AAC just doesn't have that when loaded subsonically. The ability to suppress .300AAC was heralded as among the greatest benefit of the cartridge, but as you observed, it doesn't much surpass a handgun in its energy and to me that makes the cartridge less than ideal.

outrider58 · Jan 20, 2015

I wouldn't mind seeing what difference rates of twist/same barrel length would play, if any. Say, 20'' with a 1:12 vs. 20'' with a 1:8 and so on.
Though I realize we're talking different test.

223 Barrel Length v.s. Velocity Test

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