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Fusil
July 14, 2007, 11:37
How much more muzzle rise is there between a 14" barrel with a fixed muzzle break and that of an 18" with the same muzzle break ?
Is a 16" considered much more stable than 14" or just marginal ?
A 14" with fixed FH looks great but I don't want to be pulling this thing out of the clouds.
Thanks

AndyC
July 14, 2007, 12:35
I doubt you would notice a change in muzzle-rise (apart from an increased noise and muzzleflash), because the bullet exists the muzzle quicker and rifle-powder is slow-burning.

newfalguy101
July 14, 2007, 12:46
a shorty is too short when it wont run reliably!!

unless you are talking select fire, I dont really think muzzle rise is much of an issue

ftierson
July 14, 2007, 13:11
If you shorten a 7.62x51mm NATO barrel enough, you end up with a 7.62x39mm that's really expensive to shoot...

One that also blinds you with its muzzle flash...

:)

Forrest

Fusil
July 15, 2007, 08:35
I thank you gentlemen, you have given me the confidence I needed to cut my barrel down to 14" +2". I'll just pick up some Raybans and a little 7.62X25 in case this all goes too far.

crcksht
July 15, 2007, 10:08
Originally posted by Fusil
How much more muzzle rise is there between a 14" barrel with a fixed muzzle break and that of an 18" with the same muzzle break ?
Is a 16" considered much more stable than 14" or just marginal ?
A 14" with fixed FH looks great but I don't want to be pulling this thing out of the clouds.
Thanks

A 14" with fixed FH looks great? That statement makes you sound like a mall-ninja.

Listen to ftierson, your ballistics will be no better than a 7.62x39 with ammo that costs three times as much and is heavier to carry.

shootist87122
July 15, 2007, 11:02
Originally posted by ftierson
If you shorten a 7.62x51mm NATO barrel enough, you end up with a 7.62x39mm that's really expensive to shoot...

One that also blinds you with its muzzle flash...

:)

Forrest

+1.

Get a mousegun if you want a shorty or a handy light weight rifle. IMO, the 7.62x51 is very decent intermediate cartridge (at full power) and 21" is already getting close to carbine length.

FN74
July 15, 2007, 11:15
The ballistics are still way more than a x39 with that length barrel. My FN74 has chronyed out at 2550FPS with crap ammo. It's cut at 14.5 and threaded for a permenantly attached AK74 brake made for .308 by dynasystems. Gas port is at .125 and it runs flawlessly on every type of ammo I have tried on a setting of 4.
Accuracy at 25 meters is about 3 inches high. At 100 meters she's 2 inches high. At 300 meters she's dead on. 500 meters about 4 inche low. Beyond 500 you lose a lot of velocity and drop is more pronounced. I built mine this way because I wanted the punch of the .308 in as compact yet realistic package as possible with the FAL platform. It'll shoot circles around an AK, and still uses NATO spec ammo.
I don't shoot much of anything anymore with my own ammo, I let uncle pay for my training so it has not cost me much in the last 3 years. Thank god I put away all that South African .308...

2800 FPS is about average for .308, a little less for 7.62 nato. Figure about 2650 FPS. Deduct roughly 25 FPS per inch of length you cut away on the barrel. 21" - 14" = 7" 7x25 = 175 FPS. 2650-175 = 2475FPS average for 7.62 nato, .308 is 2625 and those mean velocities are based on calculations giving the same length test barrel. AKs use a 16"+ barrel. So if you start lopping inches off it to 14", you can deduct at least 50 FPS from that mean number.

Apples and oranges. Also remember this is factoring in a 150 grain projectile for the .308 and a 123 grain projectile for the x39.
Hell for that matter, the .30 carbine is only 375FPS behind the x39....shooting a 110 grain bullet....

7.62x39 Muzzle velocity average is 2365FPS.

FN74
July 15, 2007, 11:30
Check out the muzzle energy of the round, that is the transfer of energy upon impact. The greater the number the more energy transfered.

http://www.chuckhawks.com/rifle_ballistics_table.htm

Caliber Weight MV 200 ME 200

308 Win. (150 Sp) 2820 2288 2648 1744

7.62x39 (125 Sp) 2365 1783 1552 882

For comparison:

.30 Carbine (110 RN) 1990 1236 967 373

.30-30 Win. (150 FP) 2390 1605 1902 858

idsubgun
July 15, 2007, 12:38
I have DSA's 13" Elite Compact front end on my para and there is hardly any muzzle jump.
I love this frontend. Swings easily and quickly! Can smack the 500 meter gong with it too. I'm doing another para with a clone frontend of this one.
Photo taken from DSA's web site (http://www.dsarms.com/images/00116ELITE.gif) .

http://www.dsarms.com/images/00116ELITE.gif

Gunfixr
July 15, 2007, 12:53
Well thanks guys, you just settled my worries about having cut my barrel down to 16.5". If 14.5" still hits that well, then my 16.5" won't be any worse. Making me think I could've gone shorter, though, especially since I got that long flash hider.

chrsdwns
July 15, 2007, 16:17
An semi auto SBR FAL is far superior to a short barrel semi auto AK using 7.62x39 and the FAL is scary accurate for a short barrel gun.

Short barrel rifles have an intended purpose which, when used for that intended purpose, tend to make the cost of ammo insignificant compared to the upgrade in effectiveness afforded by the 7.62 NATO round

In general, I am not a fan of SBRs, but the FAL is an exception because of it's surprisingly small reduction in ballistics, capabilities and high (higher?) accuracy in SBR configuration.

The AK in SBR configuration shoots at abot 1800-1900 fps compared to around 2300 - 2500 for the FAL with a short barrel

dougjones31
July 15, 2007, 16:55
I have a 16" carbine with the gas block moved back 4 inches to help lighten the front of the gun to help it's handling. I also chrono'd 2500 fps. I am sure there is a faster burning powder that will take the velocity right back up. I think there is plenty of room for improvement. Even loading a lighter projectile is an option.

idsubgun
July 15, 2007, 17:57
Originally posted by AndyC
(apart from an increased noise and muzzleflash)

Oh Yeah, there's a lot of that! You become real popular when you're at an indoor rifle range and start letting loose with a 13" barreled FAL.
Everyone just backs away from the firing line until you're finished.
:rofl:

English Mike
July 15, 2007, 18:13
Here's an interesting experiment to determine the effects of shortening a barrel, though it's a .223, rather than .308:

Barrel shortening (http://www.accuratereloading.com/223sb.html)

Looks pretty strange by the time they finished, even though they shortened the stock as well.

A point of interest is the accuracy - look at the 15" barrel's groups.

I presume it's to do with the harmonics.