12" 7.62 Capabilities

Groundedclk

Groundedclk

Sergeant
Full Member
Minuteman
Oct 19, 2007
115
3
41
Tilton, New Hampshire, USA
#1
I found a couple threads and no one really defines the limitations of the 7.62 out of a 12" barrel. So that is exactly what I am looking to do.

How far can I reach? While being as accurate as possible.

What is the ideal twist rate? For CQB and reaching out and saying hi.

What would be the best ammo for CQB? As far as grain, bullet type, etc.

Ideal scope based on the limitations and capabilities, with a sub $1500 price tag.
 
#2
I have shot as far as 600 yards with my 13" scar 17 if that helps, and it has a 1/12 barrel. I mainly shoot FGMM 175's and 168's. My range only goes to 600 but I think I've seen a video somewhere of travis haley shooting a 10" SBR out to 750 or something, can't remember the caliber. I believe the wind is your biggest limiting factor when it comes to stuff like this, and the fact that the round won't have as much "oomph" or may not fragment. For CQB it would be a whole lot of nastiness, extra weight and diminishing returns. 556 SBR is a better choice there. Scope would depend on what the application for the gun is so without telling us more about that I wouldn't know what to tell you.
 
#3
My main use for the gun is running IDPA and hitting the 100 - 500 yard range.

I would like to push it to it's limits and use it a primary rifle for the range, it is not my only rifle or SBR. It is my newest toy and want to set it up like run like a main battle rifle.
 
#4
I am not sure on the rifle it self but on the scope i would look at a 1-6 set up . Maybe a Vortex 1-6 or the Mark 6 1-6 . You might have to shop around on the Mark 6 or it would cost ya a couple hundred over your price but i like the reticle a bit more on the Mark 6 over the Vortex but i looked through the vortex and it has damn nice glass and a day light bright red dot with a BDC style drop down . what brake are you going with ?
 
#6
OldGuardShooter said:
I am not sure on the rifle it self but on the scope i would look at a 1-6 set up . Maybe a Vortex 1-6 or the Mark 6 1-6 . You might have to shop around on the Mark 6 or it would cost ya a couple hundred over your price but i like the reticle a bit more on the Mark 6 over the Vortex but i looked through the vortex and it has damn nice glass and a day light bright red dot with a BDC style drop down . what brake are you going with ?
Click to expand...

I was looking at the Vortex as well, you think it is worth spending the extra money for the HD version?

For a brake I am going with a YHM, because I bought a YHM 4350 to go with it.
 
#7
oh yeah i'd spend the extra on a HD version the overall scope is built better . There is a guy selling one right now i was talking to him this morning trying to figure out if i could swing it but i just can't right now . it's for sale in the new member px section. i think he wants 1200 shipped or 1350 shipped with a LaRue spr 1.5 mount. that's a good deal since the scope normally sells for 1399.00 and the mount i think is 220.00 .
 
#11
AMMOWASTER said:
Has anyone shot these short guns over chronographs? I would love to see some real life velocity out of the short barrels
Click to expand...

me too. i have seen some 12" chrono data cited on a few forums but it is usually with only 175gr or milsurp 147gr. i would really like to see some hard data for 155gr, 168gr AMAX loads and other hunting/tac style loads. been giving a 13.7" perm attach barrel with BABC alot of thought lately.
 
#12
Here's a decent and overlooked "capability" of a SBR .308

DSC04409.JPG
 
#13
Okay that HAS to be a sub 12" barrel, right? IMO a short 308 ( short for a 308, which will always come out longer than other calibers) has a few advantages over other short platforms. Most notably heavy projectiles at fair velocities. But you can't get away with going crazy short like other platforms ( see pocture above ). If your using something like a 155-168gr AMAX that expands/frags down to 1600 fps (or there abouts) and getting a muzzle velocity of around 2400-2500 fps ( which is a fair for 12.5-14.5" barrels) ....... Then your getting around 350-500 yards of fantastic bullet performance. No?

thees are all gross estimations. but i think people over exaggerate the velocity loss of 308 in 12-16 barrels. blast and noise may be another story.
 
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#14
For those ranges why not use a 6.5 Grendel?

Someone posted a funny pic above, but realistically the muzzle blast from a 12" 308 will be pretty loud especially with a muzzle break. But to each, their own.

If you want a 12" 308win semiauto go with a 1 in 10" twist or faster and use 178 Hornandy or heavier bullets.
 
#15
the heavy smk's will be good for accuracy.... but if you want a decent terminal effect on target out of a short 308 barrel, you will need a bullet that does not relay on high velocity yaw to frag/expand. you would be much better served with a ballistic tip or soft point that will expand/frag down to lower velocities. i think most hunting style expanding 308 bullets usually work pretty good down to 1800 fps. or you could go with AMAX witch will get you performance at even lower velocities still.
 
#16
Supersonic bullets out of my 9" 300 BLK have way too much noise and blast without a suppressor. It only has 20 grains of a fast powder. 40+ grains of a slower powder would make for a VERY uncomfortable shooting experience unless you are in the middle of an open field with no obstructions to send the blast back at you. Just something to consider.
 
#17
I found recoil and blast to be tiring with a 308 SBR. I have my SBR chambered in 6.8 SPC. After shooting about 40 or 50 rounds you are ready to pack it in. I also had a 16" in 308 and decided that 18" is better. I have three rifles chambered in 308 and the shortest is 18".
 
#18
The last time I shot a 13.5 inch LMTMWS, the velocity hovered around 2390 slow, 2405 fast if I recall correctly. I will be going to the range with my 14.5 LMTMWS this weekend and can let you know then for sure. I am going to compare my shooting chrony to the acoustic chronograph bought from rifles only. With beginning velocities of 2400 fps, mk316 mod o, 175 smk bh or 175 fgmm, you don't go subsonic until about 950 yds. (I only used these 3 rounds as that's what I have shot. I do have a fair amount of SW M118LR coming though.)

With the surefire socom fh, the signature was really reduced on the 13.5 and that's what I put on my 14.5. It is LOUD though :-0.
Like an old 454, built, lumpy cam, headers and straight pipes! I like it but some right next to you maybe not so much.
 
#19
I forgot to mention that recoil was really tamed with the short 308's with clint's heavy buffer and spring. My 16 inch SS LM8MWS is a kitty cat with the surefire socom brake and same clint's set up. That's just my opinion but I had a 14 year old at my last range trip loving the 16SS with brake. He shot it more as he enjoyed banging steel with the HDMR.
 
#20
Bumping this thread I hopes we will here from more sub-16" .308 owners. Some chrono data for 12-15" barrels For 130-168gr would be greatly apprietiated.
 
#22
Without a doubt; I will be on the range next Saturday and Sunday. I will chrono my 14.5 with 168 fgmm and MK316 MOD 0. I really need to run my superchrono next to my shooting chrony anyway.
 
#23
Thanks for all the velocity data guys. I always hear everyone parroting the info that short barreled 308's are no better than 7.62x39.

2400 with a 175 grain pretty much blows that out of the water. I have a 14.5" AR10 that I want to get back together and shoot some of the 110, 125, and 155 grain loads through. I am fairly confident that it will spank the AK's in every way except for weight.
 
#24
May I suggest you study the 308 pistol data available on line. There are lots of guys shooing 12-14inch tubes with a 308, and have been for a while, lots of data.
 
#25
Ammowaster,

No doubt it will spank 39. Even 300blk at 2400-2500 fps has something like 17% more energy from muzzle to end of useable flight. The major difference being the design/type of 308 round you are using. The last time I shot the 130 grain mk319 mod 0 barrier round in my 18 inch 308 LMT; I was getting right at 2,800 fps.
 
#26
Thanks Shooter. Those numbers look good.

pawprint2 said:
May I suggest you study the 308 pistol data available on line. There are lots of guys shooing 12-14inch tubes with a 308, and have been for a while, lots of data.
Click to expand...

The problem is that most of those are shot out of single shot pistols and the velocities might be close or might not depending on the application.

Silhouette shooters for instance use pretty stout loads if I remember right. That same load may not be a good choice for a gas gun
 
#30
AMMOWASTER said:
Why is that? While obviously better at subsonic work it is still quite a bit slower than the 308.
Click to expand...

I don't mean to speak on Kevin's behalf, but my take is that since you are paying the size, weight and muzzle blast penalty for a 308 platform, given the same barrel length, compared to a AR-15, you are not taking full potential of the 308 round in a barrel under 16".

I was extremely intrigues by a 308 SBR a few years ago, until reading up a lot about them, and incidentally, getting advice from Kevin to go another route.

I'm sure a 308 SBR can work, and no doubt it would punch harder than even a 300 BLK, but not by a wide enough margin to justify the cons. Hope that makes sense. At the end of the day, to each his own. If a 308 SBR floats your boat, rock on, but just be aware of the trade-offs. No free lunch, so to speak.

Man, this post is jam-packed full of cliches!!
 
#31
Another vote for the .300 BLK if you want a sub 14.5" or so .308.

The velocity loss will bring you into .300 Blackout's normal operating territory for a 12.5" or so barrel. You also have much less flash and noise (from unburned powder); higher magazine capacity with smaller mags; same bullet selection - especially for reloading; and an overall lighter package.

Why not the .300 Blackout?
 
#32
I've shot short 7.62mm guns, all the way down to 8"

16" is where my 'comfort' level is with the cartridge - based on the law of dimishing returns, in the short (12-13") guns there is a great deal of unburnt powder and the ballistics are much closer to a 7.62x39Russia than normal 7.62x51NATO.

The size of the platform, the weight, and the muzzle signature make the small guns not very small, and then your pretty much mandated to running a can - and the short cans don't do much on that size barrel.

I am not a big 6.8 fan, but for folks who think they want a short 7.62mm gun, if you don't want .300BK, then I think 6.8 is the answer.

Yes you can get into exotic ammo to make the weapon perform (I'm not talking 130gr SOST), but its still a lot of size/weight that IMHO is not needed.

The only reason for a short gun is for confined space options, and in a house or vehicle the short 7.62 is down right unpleasant.
 
#33
KevinB-KAC said:
I've shot short 7.62mm guns, all the way down to 8"

16" is where my 'comfort' level is with the cartridge - based on the law of dimishing returns, in the short (12-13") guns there is a great deal of unburnt powder and the ballistics are much closer to a 7.62x39Russia than normal 7.62x51NATO.

The size of the platform, the weight, and the muzzle signature make the small guns not very small, and then your pretty much mandated to running a can - and the short cans don't do much on that size barrel.

I am not a big 6.8 fan, but for folks who think they want a short 7.62mm gun, if you don't want .300BK, then I think 6.8 is the answer.

Yes you can get into exotic ammo to make the weapon perform (I'm not talking 130gr SOST), but its still a lot of size/weight that IMHO is not needed.

The only reason for a short gun is for confined space options, and in a house or vehicle the short 7.62 is down right unpleasant.
Click to expand...

Yeah, I learned this a while back when I tried out a buddy's LMT MWS .308 13.xx" barrel at an indoor range. Quite frankly, to say it was unpleasant is an understatement. To make things even more 'unpleasant", he had a brake on it. The resulting noise, concussion wave and face full of gas/carbon put me off of the .308 SBR idea. My shooting glasses fogged up every few shots - not with fog, but with greyish gas/carbon residue.
Long story short, 308 SBR's = multiple major tradeoffs for minimal ballistics gain.
 
#34
To each his own. I have fired thousands of rounds down a 13.5 LMTMWS 308 barrel with socom fh and never once had glasses fog up, etc. Mine slings mk316 mod o at 2,400 fps and doesn't go subsonic until about 950. Maybe I am used to it but with about 645 ft lbs energy at 800; I wouldn't want to be on the other end of it.

I will say I am not a fan of anything shorter than 13.5 and 14.5 is my overall favorite GP length if you have an accurate enough system. My 308 14.5 fluted barrel handles very well. With a geissele trigger and clint heavy buffer, it is quite controllable as well.
 
#35
Shooter0311 said:
To each his own. I have fired thousands of rounds down a 13.5 LMTMWS 308 barrel with socom fh and never once had glasses fog up, etc. Mine slings mk316 mod o at 2,400 fps and doesn't go subsonic until about 950. Maybe I am used to it but with about 645 ft lbs energy at 800; I wouldn't want to be on the other end of it.

I will say I am not a fan of anything shorter than 13.5 and 14.5 is my overall favorite GP length if you have an accurate enough system. My 308 14.5 fluted barrel handles very well. With a geissele trigger and clint heavy buffer, it is quite controllable as well.
Click to expand...

Don't get me wrong, I am not knocking it. Just pointing out that it is very different from typical SBR's, particularly in enclosed spaces. And I wouldn't want to be on the other end of it either, but that goes for any cartridge, centerfire or rimfire.
 
#37
I always wanted an LWRC 12.5" 308 until I got my 16" KAC. I can run it like my AR's now that I have the MAMS! I don't need it any shorter. I know "need" is a 4 letter word around gun boards. I can do just about anthjng with it. If I had more time to shoot I know I could run it out to 1000. Just my 2 cents! I think for anything under 16" there are other cals to run that would be better. Again just my 2cents!
 
#38
Shortest I know of is 13.5 and I have had a blast with them. Surprising accuracy and the new SOCOM FH does well. Velocity should be right around 2400 fps with mk316 mod o.
 
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