AK or AR for SBR Build?

[agould27]

My experience is gonna say AR. The ak will have a lot of recoil and muzzle blast. They are much less accurate than the AR platform. With the right muzzle brake the recoil of the AR will be close to a 22 magnum. Will be a lighter rifle and in my opinion stocks and accessories are easier and nicer for the AR.

[John A.]

Originally Posted by ZLujan

Do you know what a 9mm could reach out to effectively out of say an 8" or maybe a 9" barrel?

Is there anything I will need to really watch for with either build?

I like 9mm carbines, though I admit I don't currently have one in an AR at the moment.

8 or 9 inch barrel will easily shoot 100 yards and a little farther no problem. I have a Lage slowfire upper for my M10A1 and it can ring a gong pretty easily, and even the 5.5 inch barrel on the MP5K will do 100 yards when I do my part.

As for things to watch with a 9mm AR, make sure the hammer isn't notched on top. There are a ton of subjects on the specifics scattered all across the internet, but having a flat face (un notched) hammer is definately one of those. Some people ramp the bolt and install a heavier than average hammer spring and H3 buffer and KNS pins as well.

But that is the bulk of it.

[ZLujan]

Awesome, thank you John, I'm currently looking for three lowers now. One will be the SBR, the other a 20-22" rifle and the final one would be a 16" carbine. Cannot wait to get this build going. Again, thank you for your input. I'm excited again to get a new firearm (haven't felt this way since I bought my XDm lol).

I think I will go with multi-cal lowers and run a a 5.56 for now and then, as I get more money, I will pick up a 9mm upper, .300 blackout upper and then a start gathering suppressors. I am truly giddy about all this, it's going to be awesome!

[John A.]

Nothing wrong with having 3 complete guns, but just letting you know that you are allowed to put a 16 or 20 inch barrel upper on a sbr registered lower too as long as it is not a "permanent" change.

All NFA laws still apply though even with the title 1 uppers though because the lower receiver is the registered item.

No loaning it out to your buds if you're not there with the gun, crossing state lines requires notifiying the NFA branch, etc.

Just sayin' that you don't necessarily have to buy 3 different lowers unless you just wanted to.

Also, some 9mm silencers are also compatible with subsonic 300 blackout and 22LR rounds too. So then you'd only need to buy 1 suppressor to use on multiple host uppers to save even more money and time.

Check out the Thompson Machine ISIS-2 as an example:
http://www.thompsonmachine.net/?page_id=99

[PolsVoice]

Originally Posted by ZLujan

I am looking at building an SBR, but I'm conflicted. I cannot decide if I want to just go the AR route (it's easy to buy the upper and slap it on a lower) or if I want to run an AK. I love AK's but, as of recently, I am very interested in AR's as well, especially with the .300 AAC Blackout or the .50 Beowolf or .458 SOCOM, or any of the many other calibers.

If I go the AK route, it will be a 7.62x39 with a 10" barrel, unless I can find one shorter, and have a wire folding stock that I am thinking I may design and build myself. Additionally, I am probably going to suppress the rifle after I get the SBR stamp on it, whether it's AK or AR. And yes, I know that the AR offers calibers that are better for suppression.

10.5" barrell, underfolding stock and in 7.62x39. I love this gun.





8.5" barrell. 5.45x39. There are some in 7.62x39, too.


[/QUOTE]

Originally Posted by GAGTO

AR, you can own multiple uppers and use the same lower.

AR: 1
AK: 0

Originally Posted by John A.

SBR AK's are more rare, and harder to do, and thus worth more resale in the long run because of it.
.

AR: 1
AK: 1

Originally Posted by John A.

If you dont' have an AR, I'd start with a 5.56 upper so you can have fairly inexpensive ammo and enough ooomph for 200 yards even out of the shorter barrel.

I would recommend not doing this. The velocity loss of 5.56 out of a short barrel takes ball ammo below the speed it needs to fragment. Other bullet technologies would work, but are significantly more expensive. 9mm and other calibers, however sound like they would be great for your purposes.

7.62x39 is still an effective SBR caliber as it can still turn a cinderblock into a shrapnel grenade. It's cousin, 5.45x39 is wonderful, too.

Originally Posted by John A.

I'd probably skip the 6.5 grendel and 6.8 spc for short barrel use and consider an 5 to 8 inch barrelled 9mm upper with a suppressor for close in work when you're wanting to be quiet. It's really hard to beat a 9mm suppressed carbine using 147 gr bullets.

AR: 2
AK: 1


Other thoughts:

Suppressing any AK is a pain in the butt, not just because the action is so loud, but a lot of AKs have non-concentric threads which can lead to baffle strikes. The can get quieter, but can never compare to an AR

aaaaand here's a pic of what my SBR AK looks like.



10.5" barrel with a triangle side-folding stock. Built from an Yugoslavian M92 kit in 2008

[John A.]

Originally Posted by PolsVoice

I would recommend not doing this. The velocity loss of 5.56 out of a short barrel takes ball ammo below the speed it needs to fragment. Other bullet technologies would work, but are significantly more expensive.

Best I can remember, 223/5.56 needs about 2200 fps to adequately fragment.

223 does pretty good at keeping enough velocity to fragment down til about 6 inches using hand picked powders and the military has even used 10.5 inch barrels in service.

Here's an old web page, but does a good job showing the difference in velocity even with short barrels. It doesn't lose as much as many people think.

The Effects Of Reducing The Barrel Length On Velocity And Accuracy In The 223 Remington

[GAGTO]

I'm waiting on my SBR in form 4 hell. I've got a 16 in carbine, I also purchased a virgin lower and built a pistol with a dedicated 6 inch .22 upper. I'm currently building a 9mm upper with a barrel in the 5-6 inch range. If I want to take either of the short barrel uppers across state lines, I can put them on the pistol lower without notifying BATFE.