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Airacuda
February 18, 2012, 11:18
Last week a guy brought a chronograph to the range to try out his reloads.
He decided his rounds were too slow(2750 to 2800 fps) on his 16" barrelled AR. I tried a couple of factory Federals in my AUG(3000fps) 16" also,then I tried one of the Hornady Superformance rounds that are supposed to be 200fps faster than anything else. 3200 fps....sweet,they work! For the heck of it I asked to try one of his reloads which went 3000 in my AUG. Then his friend got involved with a Piston AR...Sig I think. Both AR's,Piston and gas imp were both on average 150 to 175 fps slower than my AUG after several rounds of various ammo. Anyone know why this would be?

cowbilly
February 18, 2012, 21:00
This is a SWAG. Could it be that the gas bleed off occurs further down the barrel on the AUG than on the AR. It seems like there is a lot of barrel left after the gas bleed off on an M4gery than on the 16" AUG. Loss of pressure for operation could be the cause or the AR requires more gas to function.

Tim Dreas
February 20, 2012, 11:13
A lot of AR15 barrels have a lot of free bore. My AUG has the standard 20 inch barrel. I had a 223 Valmet bullpup and the muzzle was too close to my face for comfort. I don't think I'd like a shorter a barrel on my AUG.

Airacuda
February 21, 2012, 11:44
Someone mentioned it could be the 1.9 twist rate compared to the 1.7 of the AR.

Airacuda
March 05, 2012, 06:11
Fired a few more rounds out of some volunteers AR's last weekend.Their speed was in the 2875 to 2925 range with 16" barrels and same ammo. They were both gas imp and not piston rifles. Upon noting the faster speeds than the previous AR's and me telling them about our theory. They checked and both AR's with pencil barrels were 1.9 twist.
So they are faster than the 1.7 twist but not as fast as the AUG. Our gunsmith says it has to do with the chamber size,tolerances,vertical angles and the congruent sides of the isosoles hipotonoose......or something like that.:uhoh:

Insider
March 29, 2012, 10:47
Your comparing a Porsche to a Chevy.

Airacuda
March 29, 2012, 21:25
"Thats funny....I don't care who you are...That's Funny!"

Insider
March 30, 2012, 00:42
"Thats funny....I don't care who you are...That's Funny!"

I'm just an old timer who has recently discovered the beauty of the AUG.:aug:

Airacuda
April 18, 2012, 13:30
Had the chronograph out at the range last weekend and fired a few rounds thru the A3 and my friends Core 15 AR with 16" barrel. Very interesting results.
Firing 62 grain ammo from Silver bear....a nickel coated steel case ammo which I like and functions perfectly. Both weapons got the same results at 2830 to 2880 fps. When firing 55 grn federals the AUG was again faster by 100 to 150 fps.2850 vs 3000 average 3 shots each.
A very anal guy at the range thinks it may be how far back the rifling goes into the chamber,or a reasonable faximile therof. With the longer rounds of 62 gn the bullet in the AR reaches the rifling making similar speed to the A3, but the shorter 55 gn does not reach the rifling making it slower than the A3.
Basically the A3 has tighter chamber with rifling starting sooner.
Make any sense?

Zeusizme
April 18, 2012, 18:22
First I don't own an AUG yet, but it is on my list of need to own. I would venture a guess that the powder burn rates are different between 55gr and 62gr. Measure the distance from the chamber to the gas port and see what the differance is between the AUG and AR. I would think that the AUG's gas port is located closer to the muzzle then the AR's port. But that still may not explain the simular performance using 62gr bullets. Twist rates of the barrel will also produce variations in fps. Then you also have identical guns which produce different fps.

hagar
April 18, 2012, 18:28
Gas bleed off should make very little difference. Does the AUG have a polygonal barrel like a Glock? They are known to shoot faster.

open ear shooter
April 20, 2012, 06:48
The N.Z Army shooting team use's the 16" AUG barrel stating it's more accurate than the 20" ? can anyone explain that !

homelandprotector
April 20, 2012, 14:10
The N.Z Army shooting team use's the 16" AUG barrel stating it's more accurate than the 20" ? can anyone explain that !
I've heard that the average 223. round burns all the propellant within a 14" - 16" barrel.......so after that point a longer barrel puts drag on the bullet, kinda like putting on the brakes, slowing it down and reducing trajectory.

I had a Bushmaster Predator with a 24", absolutely mind blowing accuracy but sure enough it had slower velocity.

http://img80.imageshack.us/img80/7591/china06217aa6.jpg

Now give me a Knights Armament 308. Jhaidst slayer with a 20" barrel and everyone is happy........

http://img211.imageshack.us/img211/3058/sass13po.jpg

hagar
April 20, 2012, 19:49
I got 200 feet/sec more velocity out of a 22 inch bull barrel AR than my 20 inch NM rifle with the 75 Amax over 24.7 grains of RL15. These were loaded to 2.45 oal for single loading, so maybe not a good comparison.

Airacuda
April 21, 2012, 10:28
I will take my A3 out this week and use both 16 and 20" barrels and put that to the test.
I have on hand Hornady superformance 53grn varmit ammo,Pmc X-tac 62grn,Silver bear 62grn Soft pt,federal AE223 and American eagle 50 grn hollow pt flat tail ammo.
I'll put 3 rounds each thru both barrels and report back.
I'll also use an AR if one is around....which they usually are.