Short barrel options 300 AAC or 308

[Glassaholic]

Looking for some helpful advise here. I have two LMT's: a 5.56 16" CQB MRP Piston and a 7.62 LM8MWS 20". I should have my suppressor this fall and was thinking about a short barrel option. LMT makes a 10.5" 300 AAC barrel and a 13.5" 308 barrel. The 300 AAC option would obviously be lighter but then I'd have to get reloading equip for a whole other cartridge etc and ammo isn't cheap and shells aren't prevelant. the AR-10 would be heavier but I can use the same exact gear to load rounds for both super and sub-sonic ammo. I am leaning toward the short bbl 308 platform but am wondering if there are any other issues at play? I know I can get 30 rounds vs 20 of AAC vs 308 but that's not a huge deal breaker. Will either give me problems suppressed with sub-sonic ammo? Will the small/fast powder gunk up my suppressor more with sub 308 loads? I'm sure there are things I have not yet thought of so thank you for your help.

Bill

 

[wfjames22]

Do you plan on using the gun as a single shot or semi auto when shooting subs? If single shot, go .308 and if you want to shoot semi auto, go 300blk. My MWS with the 13.5" barrel, loaded 20rd mag, Leupold mk4 3.5-10x40 and titanium suppressor weighs 14lbs. My 300blk with a 10.3" barrel, same scope, same suppressor and loaded 30rd mag weighs 9lbs...big difference, depending on what you are going to use it for.

 

[Glassaholic]

Thank you wfjames22, that does help. I didn't realize it could be a 5 lb difference, that is huge and definitely something to consider. I'm assuming what you mean by "single shot vs. semi auto" is if I intend to shoot tight groups on paper then I will probably be happier with the .308 vs. if I want to just fire away and have fun then the 300 is probably going to be better for the "fun" factor. Interesting thought...

 

[rjacobs]

If you go short barrel, gotta do the tax stamp. Cant just slap one on.

And 300BLK, yea reloaders caliber right now, but im hearing things will open up here shortly once Remington gets things rolling again.

There are plenty of 300BLK casings too. I think I have 30k ready to ship out.

 

[wakajawaka]

Short barrel and supressor will play nice with the Blackout,
Not sure how short you can go on the .308 and stay safe. Check with your suppressors manufacturer for advice there.

 

[Rogue111]

I myself am in the process of putting together a 300BLK SBR. It was designed to run subs out of an SBR.

 

[Nortonious]

Been tinkering with 300BLK for a couple years. Got a couple bolt guns and AR's (one 16" and one 10.5"). Also have AR-10s and bolt gun 308's. My thoughts:
- for suppressed subsonic semi-auto 30cal I'd def go 300BLK
- I prefer my 10.5" 300 BLK AR for subs (don't need the long barrel just to go slower)
- build your own 10.5" upper, with the money you save put a carbon fiber handguard on there. Even with the can hanging, this gun will be light light light.
- I do sometimes shoot subs out of my 16" platforms and my 300BLK loads are designed to stay subsonic in those guns, so I give up a little fps in my 10.5" (but I don't feel like loading 300BLK subs for specific barrel lengths)
- supersonic 300BLK has good energy, but obviously not a 308.
- I've been using 155gr family for my supersonic (tried Amax, Berger VLD, and SGK). This seems to give the best down range energy at 200yds (I won't bore you with all my data...it was a bit OCD). I have friends who like the 125gr in their 300BLK cuz it shoots flatter.
- subsonic bullet expansion can be problematic (ie in killing hogs). I just got some 194gr Lehigh that I need to load up....supposed to do the trick
- as far as "sneaky" subsonic multiple hog sniping...it doesn't really work much. They still hear noise (ie their buddy getting whacked) and get spooked and start running, so I find I just shoot suppressed supersonic ammo most of them time and have a mag of subs ready just in case.....or sometimes we just shoot subs cuz we want to and its America by God and we can.

FWIW-308 is a great hog killing round and having a few subsonic 308 rounds (Trail Boss works good) handy for that "special shot" might be the best answer

 

[wfjames22]

I'm assuming what you mean by "single shot vs. semi auto" is if I intend to shoot tight groups on paper then I will probably be happier with the .308 vs. if I want to just fire away and have fun then the 300 is probably going to be better for the "fun" factor. Interesting thought...

You know what assuming does, right? Ha...surely an issue with clarity on my end...been at home laid up with the flu for the past two days and my brain is a little scrambled.

What I actually meant was that if your goal is shooting subs with a can, you are not going to get your 308 to cycle...therefore you will be cycling the bolt by hand. That is not the case with a 300...subs will run in that baby all day long.

Here's a video of me running the first 300blk I had (16" bbl) on steel @ 100yds with 220gr smk subs.

 

[TexasGunTrustLawyer]

The 300blk is designed as a 30cal subsonic cartridge with a 9" barrel as the stArting point.


If subsonic 30 is the mission, then a 300 Blk. Sbr Is the solution.

308 will be more accurate. But the 300blk rocks out of a 9" barrel.

 

[Glassaholic]

What I actually meant was that if your goal is shooting subs with a can, you are not going to get your 308 to cycle...therefore you will be cycling the bolt by hand. That is not the case with a 300...subs will run in that baby all day long.

Thank you again wfjames22, sorry you haven't been feeling well and appreciate your input in your cloudy state. That actually was what I was wondering based on other things I have read so thank you for confirming that. Yes, my main goal with this is shooting subs with a can and the cycling issue is a definite drawback to the 308. In fact, it renders the 308 option as obsolete because I need it to cycle with the suppressor. It sounds like the 300 AAC was designed for sub-sonic shooting to begin with and everything about it was for reliability with the AR-15 platform so I think this should be the way I should go.

Also, Nortonious, you bring up a good point about building my own upper, my CQB MRP is not the lightest of the bunch. Does anyone know how much weight savings can be achieved with a lighter upper vs. my current LMT MRP? Right now, my LMT weighs 8lbs 6oz with an EOTech on it, the LMT iron sights are 6oz for the pair so I could shed some weight with some Magpul MBUS. My upper alone with the EOTech (12oz) weighs 6lbs even, a 10.5" bbl vs. the existing 16" would maybe save 1 - 1.5lbs maybe? I'm guessing here. So sticking with the MRP upper and going with the 10.5" bbl I'm looking at about 5 lbs, maybe a tad less or about 4lbs without the EOTech and LMT sights...

I'm probably way over thinking this (as I usually do) but this gives me food for thought. One last thought, I've read that the shorter bbls with 5.56 can wear out a suppressor much quicker, is this the same with 300 AAC? Would I be better off with a 12.5" bbl vs. a 10.5" or less?

Thank you all

 

[Glassaholic]

But the 300blk rocks out of a 9" barrel.

Thank you TGTL, but does it not "rock" out of a 12.5" barrel? Will I see a little more accuracy (I'm assuming, but like wfj said, we all know what happens when we assume) with supersonic ammo out of the 12.5" vs. 9" or when they are that short is it a wash? My local Smith says he can shoot accurately out to 800 yards with his 12.5" AAC upper with supersonic ammo, that is pretty impressive to me, of course, he was trying to sell me a 12.5" AAC upper as well sooooo...

 

[peaceatwar]

If truely want versatility, a 30 cal bullet in an AR-15 platform. Check out the 30 ARX.

30 ARX

Velocities over the 300 BLK are there and you can still make subsonic loads.

 

[TexasGunTrustLawyer]

Thank you TGTL, but does it not "rock" out of a 12.5" barrel? Will I see a little more accuracy (I'm assuming, but like wfj said, we all know what happens when we assume) with supersonic ammo out of the 12.5" vs. 9" or when they are that short is it a wash? My local Smith says he can shoot accurately out to 800 yards with his 12.5" AAC upper with supersonic ammo, that is pretty impressive to me, of course, he was trying to sell me a 12.5" AAC upper as well sooooo...

The 9" barrel is quieter than the longer barrels with subsonics. We actually shot the subsonic blackout with a Gemtech Sandstorm on a 9" and a 16" barrel and everyone agreed that the 9" was noticeably quieter.

A quality barrel will shoot accurately as long as it is long enough to stabilize the bullet.

ETA: the 12.5" barrel will be fine. I just like the shorter barrels for subsonic performance

 

[Nortonious]

The 9" barrel is quieter than the longer barrels with subsonics. We actually shot the subsonic blackout with a Gemtech Sandstorm on a 9" and a 16" barrel and everyone agreed that the 9" was noticeably quieter.

Hmmm, interesting. That seems counter-intuitive to me. Pistol length gas tube on the 9" and carbine length on the 16" ?

Assuming you were shooting the same ammo thru each, I wonder if some of the airflow on those subs in the longer barrel was transsonic (while the bullet itself was still actually subsonic ) and hence a little louder. I may have to try this experiment myself. Any idea of your MV's ?

I know with my suppressed 22 subs, the very slow Quiet-CB ammo is much quieter than the faster, yet still subsonic ammo, but I simply attributed that to a lighter powder charge.

 

[Glassaholic]

So who all makes short barrels for the AR platform? Here's what I could find with a little digging -

ACC
Noveske
CMMG

 

[ss355]

A few other Blackout shorty makers off the top of my head:

Palmetto State Armory
Black Hole Weaponry
Wilson Combat
AR Stoner

 

[wfjames22]

Daniel Defense, Rainier Arms, Bravo Company, etc....pretty much everyone who makes AR barrels, more often than not.

 

[Glassaholic]

I just found another one, never heard of them, has anyone here ever heard of them?
HM Defense

 

[jwb47]

the whole reason I got into the 300 blackout was my lar-8 was a pig with the suppressor on the end the 300 was an outgrowth of that . since then I now have an 8.5 inch cmmg pistol , a 16 inch carbine and a remington 700 . by far the 8.5 is the easiest to handle. I dont shoot long range with it but where I hunt 75 yds would be a long shot . I plugged a spike buck at 50 yds with an outlaw state expanding sub and he died where he stood . last year I shot a doe at about 35 to 40 yds with the same results . so if hunting is your bag then thats about the best I can offer . I have shot super sonics with the pistol out to 100 yds but I have an aimpoint pro and old eyes so about 4 inch 10 shot groups was about the best I could muster . just a heads up but while trolling midway last night they have the 10.5 inch stoner barrel in stainless steel and light weight contour in stock for around 220.00