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View Full Version : AR Pistol: 300BLK vs 7.62x39, barrel length


Junkie
08-29-2014, 8:45 AM
I'm planning on putting together a pistol before too long. I know that 5.56 doesn't do so well out of short barrels so I was thinking of going with a different round.

300BLK would be cheaper to build, especially as I have a spare 5.56 BCG around and I could use magazines that I already have. Ozark has ammo for ~.58 a pop, and I'd probably use it as an excuse to get into reloading.

7.62x39 would be cheaper to shoot, as ammo can be had for $.22 a pop. However, it would cost more to build as I'd need a specialty bolt and magazines.

For either one I'd want to go with a ~10" barrel. I'd like to go with a Sig brace but for now I'll wait on figuring out if it's legal in CA.

I'd like something fairly reliable. I don't expect to use it for HD, as if anything happened having used a "ghost gun" wouldn't look so good, but I don't want a gun that's likely to be problematic.

If this should be in the pistol forum feel free to move it, but I think it makes more sense here.

Thanks for any advice.

thetaxman
08-29-2014, 8:52 AM
My only comment would be not to discount the 5.56 round so quickly - 10.5" is just fine for 5.56 out to many hundred's of yards.

All of the above sound like good options to me, but definitely check in with others on the Sig brace part. That seems to be a very gray area right now in CA.

CK_32
08-29-2014, 8:57 AM
I still don't get the interest to have x39 in an AR, especially after 300blk was born. Not trying to poo poo anyone, just always found it weird. I never saw that round as modern tech. Just popular due to the 47 platform and nostalgia/cheap. Only reason I own x38 and an AK. Everyones gatta have an AK :D

Mossy Man
08-29-2014, 9:04 AM
I'm no expert but I understand 7.62x39 ARs can be tempermental due to cartridge design. At least with 300blk its going to be reliable.

Junkie
08-29-2014, 9:14 AM
My only comment would be not to discount the 5.56 round so quickly - 10.5" is just fine for 5.56 out to many hundred's of yards.

All of the above sound like good options to me, but definitely check in with others on the Sig brace part. That seems to be a very gray area right now in CA.As I said, I'd like to go with a Sig brace but not until legality is a little more certain. I still don't get the interest to have x39 in an AR, especially after 300blk was born. Not trying to poo poo anyone, just always found it weird. I never saw that round as modern tech. Just popular due to the 47 platform and nostalgia/cheap. Only reason I own x38 and an AK. Everyones gatta have an AK :DPrice. It's hard to beat $.22 a pop. Of course I have a 5.45 AR too...

Junkie
08-29-2014, 10:10 AM
Also, I forgot to ask: does CA have constructive possession of SBRs as a state law? Meaning if I'm on my way to NV for a class and I have an AR pistol and Sig brace, not installed, is it legal?

CK_32
08-29-2014, 10:10 AM
As I said, I'd like to go with a Sig brace but not until legality is a little more certain. Price. It's hard to beat $.22 a pop. Of course I have a 5.45 AR too...

Now 5.45, that's a whole different story :D

THEJAPINO
08-29-2014, 10:12 AM
So how do 7.5"-8" 7.62x39 AR's run. I have a 10.5" 5.56 right now and had a 7.5" 5.56. I'd like a shorter/cheaper to shoot fun gun that still has decent ballistics for a possible pig hunt. Are 7.5" x39 ar's good for that?

Click Boom
08-29-2014, 3:45 PM
7.62x39 is loses a lot less out of a short barrel than 5.56

As others have said, 300blk is similar but is only good if you're setup for reloading because the rounds are 4-5x as expensive!

7.62 x39 only loses like 200 fps outta the 10 inch bbl.

glorified_welder
08-29-2014, 10:48 PM
The ballistics of 300 aac is extremely similar compared to 7.62x39. I just converted my 5.56 pistol to x39. Iv been running a x39 ar for the past few years due to the low cost of ammo. As long as you dont cheap out on the build you wont have any reliability issues. Especially if you go with the liberty bolt.

dtrump
08-29-2014, 11:34 PM
Tough question
X39 gives you cheap ammo, but seems to have problems commonly in the platform, whereas 300 aac blk is more reliable, but twice the price-- cheaper build though too as you already have the bcg. If it was me and I had 100% reliability out of x39, id do that route. But if you have been wanting to start reloading and feel this will kickstart it, 300 is a good choice.

As I stated before, its a tough question.

Click Boom
08-30-2014, 12:20 AM
it all hinges on whether or not you are prepared to start reloading for 300blk. There is nothing about it that is cool enough to justify $1.10 a round, except maybe some hunting applications.

you could be shooting 300 win mag factory loads for cheaper than that, the round is overpriced commercially.

Junkie
08-30-2014, 2:12 AM
You can get 300BLK for a lot less than that. http://ozarkordnance-com.3dcartstores.com/300-AAC-Blackout-150gr-FMJ-Qty-50_p_14.html is an example at $.58 a pop for new ammo. Not sure what shipping costs, and clearly it's a lot more than 7.62x39 still, but it's well under $1.

glorified welder, what's your setup?

Click Boom
08-30-2014, 4:12 AM
[QUOTE=Junkie;14773875]You can get 300BLK for a lot less than that. http://ozarkordnance-com.3dcartstores.com/300-AAC-Blackout-150gr-FMJ-Qty-50_p_14.html is an example at $.58 a pop for new ammo. Not sure what shipping costs, and clearly it's a lot more than 7.62x39 still, but it's well under $1.

glorified welder, what's your setup?[/QUOTE

I didn't realize it had gotten that cheap, I mean it seems inevitable it's made from cheap brass and doesn't have a lot of powder... still.. that is almost 2.5x the price of 7.6 x39 and 15 cents more expensive than 308 ammo that will put that same 150 gr projectile downrange at 2800 instead of 1900.

http://ammoseek.com/ammo/308-winchester

So it just doesn't have a place for me, but it could for you if you roll your own.

Junkie
08-30-2014, 11:14 AM
In order to get brass 308 you're spending $.60 a round, so $.58 seems a little high but not unreasonable.

jmitchell
08-30-2014, 5:56 PM
IME, 300BLK is either the expensive factory ammo (Remington Hog Hammer or Barnes Vor-Tx -- both of those shot great supersonic) or reloading (for both super- and sub-sonic). I tried a bunch of the reman'd loads and have had at least some problems -- hell, I've tried 2 different lots of the Ozarks and > 50% were well out of spec and that's just frightening.

FWIW, I think it's a much better if you reload since you you can tune your reloads the match whatever length barrel you end up choosing.

Junkie
08-30-2014, 6:05 PM
is the Ozark stuff reloads? I don't see anything about that on their web site.

How were they out of spec? That's a pretty crazy number of them to be wrong.

jmitchell
08-31-2014, 12:30 AM
is the Ozark stuff reloads? I don't see anything about that on their web site.


For the prices they are quoting? Absolutely. :-)

"Our 300 Blackout rounds are manufactured with new projectiles and remanufactured mil brass."

The bullets in each batch were the same but the brass has a wide variety of headstamps and they were NOT all military headstamps.


How were they out of spec? That's a pretty crazy number of them to be wrong.

Here's the link to my post on the 300BLK forum...
http://www.300blktalk.com/forum/viewtopic.php?f=140&t=87404

I also have a slew of pictures that I took that I sent to Ozark to prove it (sent to them in my support emails). Other customers have (privately) told me that they have had similar, if not as extreme, results as well.

It sad 'cause I want to support the small suppliers who are supporting this round but I've stopped and am reloading this myself.

fredr1980
08-31-2014, 12:54 AM
You should get the 7.62x39... similar ballistics versus the 300 Blackout but cheaper to shoot/reload. Also, unless you reload you'll have a harder time finding 300 Black out ammo versus 7.62x39 ammo and when you do it'll be way more expensive.

Reliability wise I have 30+ 7.62x39 mags and they all work 100% across all 3 of my 7.62x39 AR's :cool2:, just make sure that whatever barrel you get that the ramps on the barrel extension are wide enough for the 7.62x39. I had to do some minor "adjusting" and polishing of the ramps (took down some of the middle lug on the ramp) on my 7.62x39 pistol but after that and an adjustable gas block it was 100% reliable ;). Both of my rifles are mid-length barrels so bolt reliability/longivity is not an issue, same concept with getting an adjustable gas block for the pistol.

Fred R.

http://i101.photobucket.com/albums/m47/fredr1980/AR/IMG_2749_zpsc58afddd.jpg (http://s101.photobucket.com/user/fredr1980/media/AR/IMG_2749_zpsc58afddd.jpg.html)
http://i101.photobucket.com/albums/m47/fredr1980/AR/IMG_2752_zpsf4617fb9.jpg (http://s101.photobucket.com/user/fredr1980/media/AR/IMG_2752_zpsf4617fb9.jpg.html)
http://i101.photobucket.com/albums/m47/fredr1980/AR/IMG_1562.jpg (http://s101.photobucket.com/user/fredr1980/media/AR/IMG_1562.jpg.html)

CrossedRifles
08-31-2014, 1:09 AM
No intention to derail but I've been dying to ask this question..

Is a .300 Blackout (KAC SR-30) lower receiver, in spec to a AR-15 lower?
Yes, I do know it is compatible, but compatible doesn't always mean identical in spec or function.

jmitchell
08-31-2014, 11:11 AM
No intention to derail but I've been dying to ask this question..

Is a .300 Blackout (KAC SR-30) lower receiver, in spec to a AR-15 lower?
Yes, I do know it is compatible, but compatible doesn't always mean identical in spec or function.

I don't personally know about the KAC SR-30 but...

The only change to a rifle to make a .223/5.56 AR into a .300BLK is changing the barrel. Everything else is the same.

Though for ease of swapping, it's nicer to a have a dedicated .300BLK upper.

FWIW, to keep from confusing magazines that I have loaded for each of those calibers, I use MagPul for .223 and Lancer's for .300BLK. That way they feel different as well as look different.

Junkie
08-31-2014, 4:15 PM
What 7.62x39 pistol barrel/bolt should I go with in that case?