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Posted: 1/10/2006 11:30:10 PM EDT
Any idea how long barrel it would take to get full powder burn with .308?
Link Posted: 1/11/2006 12:24:29 AM EDT
18" give or take.

Matt
Link Posted: 1/11/2006 4:30:30 AM EDT
[Last Edit: 1/11/2006 5:09:25 AM EDT by Yojimbo]
Other than getting less velocity what else happens when you don't get full powder burn?

I'm assuming it can't be too bad since it seems that 16" 7.62 "battle" carbines pretty popular.
Link Posted: 1/11/2006 4:51:14 AM EDT
I think a exponintial growth in muzzel flash.

Matt
Link Posted: 1/11/2006 5:27:17 AM EDT
Remember though that you still increase muzzle velocity of the round after the full powder burn point, due to the time the pressure has to work.

Link Posted: 1/11/2006 8:13:39 AM EDT
FN,Imbel & FMAP went with 17.35" for their FAL Para carbine barrels. I've always pressumed that was the optimal trade off point between barrel length and velocity loss.
Link Posted: 1/11/2006 8:24:51 AM EDT
[Last Edit: 1/11/2006 8:26:27 AM EDT by Green0]
If you don't use a Vortex I'm guessing you'll be seeing a noticeable flash at even 24inches.
Link Posted: 1/11/2006 4:58:25 PM EDT
i remember reading somewhere (in a gun mag within the last two years) that it was in the 6' area for complete powder burn in a .308
Link Posted: 1/11/2006 6:39:14 PM EDT

Originally Posted By advntrjnky:
i remember reading somewhere (in a gun mag within the last two years) that it was in the 6' area for complete powder burn in a .308



Day'um... I would not want to have to pack around a 72" barreled rifle!

.308 punt gun?
Link Posted: 1/11/2006 7:01:57 PM EDT
[Last Edit: 1/11/2006 7:08:34 PM EDT by TXscout]
18.25 inches for full powder burn, if I remember correctly.

17.3 minimum preferred length on some testing done, as I recall, by FN on barrels for their FAL para's and 17.25 was the absolute minimum preferred length after testing by Crane NSW on what is referred to as the "Crazy Horse" M14 variant (sorta Like Springfield SOCOM)---Please correct me if I am wrong.
Link Posted: 1/11/2006 7:02:02 PM EDT

Originally Posted By Green0:
If you don't use a Vortex I'm guessing you'll be seeing a noticeable flash at even 24inches.



Nah. My 20" Remington doesn't have any noticeable flash in the daylight, and only a very tiny flame at night (M118LR or Fed GMM ammunition). 18" seems to be about where they start getting flash-y.
Link Posted: 1/11/2006 7:09:03 PM EDT

Originally Posted By TXscout:
18.25 inches for full powder burn, if I remember correctly.

17.3 minimun suggested length on some testing as I recall from FN on barrels for their FAL para's and 17.25 was the absolute minimum preferred after testing by Crane NSW on what is referred to as the "Crazy Horse" M14 variant (sorta Like Springfield SOCOM)---Please correct me if I am wrong.



The testing we did for urban sniper applications concluded that 18" was the shortest pratical barrel, beyond this was a point of diminishing returns and the tests strongly support that full powder burn at or near this point. From 24" down, the FPS loss per inch of barrel was minimal, but at 18" the loss started to increase noticably for each inch of barrel cut off...
Link Posted: 1/25/2006 8:29:45 PM EDT
For some reason I was thinking about 18" for .308.
Link Posted: 1/25/2006 8:31:37 PM EDT
For some reason I was thinking about 18" for .308. Thanks for the input everybody. That makes me wonder what would be ideal for 7.62x39mm.
Link Posted: 1/25/2006 9:45:23 PM EDT
[Last Edit: 1/25/2006 9:49:24 PM EDT by Randall_Rausch]
Link Posted: 1/26/2006 6:08:21 AM EDT
In talking with the Chandlers a few years ago on a .308 build they advised that at 18" you had pretty much optimal burn and velocity without getting into a longer and heavier barrel. It was their position that past 18" you weren't getting much more in terms of velocity for the amount of weight/bulk that you had to put up with on longer barrels.
Link Posted: 1/26/2006 9:53:37 AM EDT
Everything changes with the chamber cut, bulle type, powder load and type, type of rifling, type of gas system etc. You cant just say 18" and have that be a cast in stone rule. What is true for a bolt gun maty not be true for an AR10 and for an AR10 may not be true for an M1A. 150 grain ammo will not be the same as 175 etc.

You need to determine what load you will be using and what velocity figures you are requiring as well as what overall bulk/weight/length is acceptable to determine what barrel length you want.
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