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View Full Version : Subsonic 300 blackout versus pistol calibers in short barreled PDW and SMG



barnetmill
02-02-2019, 01:47 PM
There is a thread here on how glock magazines are not really compatible with AR15 frames, but we know the 300 blackout with standard AR mag works very well with the AR platform.

Question: is there any superiority of the 9x19 Luger load versus a subsonic 300 blackout? When subsonic the 300 blackout is just a little faster than the .45 acp. Since I am now into the AR platform, I would like to stay with it for my choices as much as is practical.

Dorkface
02-02-2019, 02:08 PM
9mm has a better choice of expanding bullets vs. subsonic .300 blk. Subsoinc .300 penetrates better. That's about it as far as I can tell. There are a couple choices with a couple more coming for expanding subsonic .300. Subsonic .300 isn't that loud. Especially out of a 16" barrel.

Some might say muzzle blast but I don't find it to be a big difference. Even in an enclosed shooting area. Last month I was shooting some .300blk 125 super sonic loads and the guy in the bay with me thought I was shooting suppressed 9mm because after the bang he could still hear the round wizzing through the air down range.

Add a can and things become even more overlapped.

Add full auto and they are the same in handling.

Gabriel Suarez
02-02-2019, 02:18 PM
My opinion -

The AR Platform is best with 5.56 and 300 BO. Not with 9mm. 300 BO has the distinction of having so many loads for it that you can go slow and silent for indoors and fast and loud outside. The super sonics come close to the 7.62x39.

You want a 9mm, get a dedicated 9mm sub gun equivalent like an EVO, or similar.

Brent Yamamoto
02-02-2019, 02:32 PM
IMO the best use for a 9mm AR is as a range training tool. Set it up just like your rifle caliber as an understudy. It can be used in ranges where rifle calibers aren’t allowed. More pleasant to shoot indoors, useful for training other members of the family, etc.

I haven’t set one up that way because it’s not high on the priority list. But I think it makes some sense and is the only use
I would have for a 9mm AR.

For social work I would rather have a real sub gun.

barnetmill
02-02-2019, 02:44 PM
IMO the best use for a 9mm AR is as a range training tool. Set it up just like your rifle caliber as an understudy. It can be used in ranges where rifle calibers aren’t allowed. More pleasant to shoot indoors, useful for training other members of the family, etc.

I haven’t set one up that way because it’s not high on the priority list. But I think it makes some sense and is the only use
I would have for a 9mm AR.

For social work I would rather have a real sub gun.

Off topic, but what you think of the .22 conversion kits for the AR as training aids.

Brent Yamamoto
02-02-2019, 02:58 PM
Off topic, but what you think of the .22 conversion kits for the AR as training aids.

I have a Smith 22 that I have never even shot. They make some sense as an under study weapon but... honestly I have only ever used my actual ARs. I think there is some value if you set it up right. Though today I think I’d rather just set up a specialty 10/22.

All depends on on what you use em for I suppose.

EDELWEISS
02-02-2019, 03:33 PM
For social work I would rather have a real sub gun.

Enlighten me on this?

TwoBodyOneHead
02-02-2019, 04:30 PM
My first post here. Buddy pointed me in this direction as you are talking about just the question I'm having.

I'm interested in understanding thoughts on the relative pro and con of 300blk subs vs 9mm for CQB. Ignoring the platform for the moment. Just considering raw terminal ballistics.

You are at home and The Good Lord has given you the privilege of a home invasion. Would you pickup the MP5 or the Sig Rattler loader with subs. Both have a can on them.

Dorkface
02-02-2019, 04:51 PM
More pleasant to shoot indoors.

Having stood arms length away from parallel with the muzzle for both 9 and 300 (sub and super) in semi and full auto the blast difference isn't noticeable enough to me or those whom were with me. A super has about double or a little more powder charge, of the same type of powder, then a 9mm and a sub is a grain or so more for .300blk. Its a benefit of how efficient the .300 blk round is. It could be similar to the difference of a standard 9mm and a +P load.




For social work I would rather have a real sub gun.

Between a 9mm AR and a 9mm SMG? Agreed. For me to choose a 9mm smg over a .300 blk pistol the smg would have to fit a niche I need like fitting into a tiny case, nook or something like that.

I have had the benefit of shooting a bunch of SMGs (full and semi) and a bunch of .300 blk in semi and full auto. I even had the chance to shoot a full auto mp5SD side by side with a full auto AR15 SBR w/can in .300blk. The mp5SD was a tiny bit more quite when standing next to the gun and shooter but at 10 feet they sounded the same.

Some might think I am crazy but this is what a small group of us concluded after a bunch of side by side comparison.

EDELWEISS
02-02-2019, 05:17 PM
IDK, I think the real advantage of 300Blk, is that it can fire both super and sub. In super its a good killing round. In sub its quiet and reaches further than pistol calibers. There are places for 300 in super and sub sonic and places for a SMG. I still have a place in my heart for SMGs (semi and select), and Id probably opt for a SMG more often than most (if I could find a good 10mm SMG option, Id choose that even more); but a 300Blk AR is a lot more versatile for most folks under most situations.

Brent Yamamoto
02-02-2019, 05:50 PM
Dorkface, we are on the same page.

Brent Yamamoto
02-02-2019, 05:53 PM
If you want a boutique caliber sub gun (10mm, 357Sig, hell even 40) the easy answer is the Glock PDW.

barnetmill
02-02-2019, 06:02 PM
IDK, I think the real advantage of 300Blk, is that it can fire both super and sub. In super its a good killing round. In sub its quiet and reaches further than pistol calibers. There are places for 300 in super and sub sonic and places for a SMG. I still have a place in my heart for SMGs (semi and select), and Id probably opt for a SMG more often than most (if I could find a good 10mm SMG option, Id choose that even more); but a 300Blk AR is a lot more versatile for most folks under most situations.
One big disadvantage of the AR is that the buttstock with the buffer tube can not be folded and still have a functional gun.
In contrast many SMGs have folding stocks that make them more portable and concealable.

Dorkface
02-02-2019, 06:05 PM
Dorkface, we are on the same page.

I wasn't intending to sound argumentative if I was lol. :finger:

Redneck Zen
02-02-2019, 06:38 PM
Off topic, but what you think of the .22 conversion kits for the AR as training aids.


I have a Smith 22 that I have never even shot. They make some sense as an under study weapon but... honestly I have only ever used my actual ARs. I think there is some value if you set it up right. Though today I think I’d rather just set up a specialty 10/22.

All depends on on what you use em for I suppose.

I have a Tactical Solutions M4 upper in .22 rimfire that I never use. I love the idea of a rimfire trainer for this system, but quite frankly, after the honeymoon was over I kinda lost interest. The cost of 5.56 isn't that bad if you're really training and not just doing magdumps.

I'm not saying don't get a rimfire trainer or upper. I do think they have value for the uninitiated who want/need to get familiar with the system. Plus, you can shoot them at an indoor range that doesn't cater to centerfire rifles. And it does function and look cool with a suppressor, so there's always that. But if you're like me and have been around M16s since 1973, it just doesn't beat the real thing. Which is really disappointing the more I think about it and the accessories and all the freakin' mags I got for it. I'd rather shoot 556, even if it costs me a little more. If I'm gonna shoot a semi-auto rimfire it's gonna be a 10/22 and maybe even a braced Charger like Gabe suggested.

Then again, maybe it's for you. You'll have to try one and see.

dukeodie
02-11-2019, 05:38 PM
The main problem is limiting yourself to subsonic rounds.I carry a .300W AR 10.5 with SB brace,a superb stopper with 115 gr Controlled Chaos rds from LeHigh.I've shot 2-250lb hogs and the results are devastating to say the least...on an upright biped-nasty.As it's a pistol,my CCW covers it in all my surrounding states.I can carry loaded in my vehicle,I can't with a rifle.Only use Lancer mags for .300,that way there's never a mixup with .556 mags.Can hit 6" steel at 300yds,good enough for a pistol.Irons and a HiLux red dot which is very small and has lasted 3yrs so far.LaRue trigger,nice shooter.