What caliber for an ar sbr

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horsemen61

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Ok guys I have a stripped lower I purchased as such and I would like to turn it into an sbr so A can I do this with lower B if yes to A what caliber would you do it in and C what barrel length would you go with

Thanks horsemen61
 
Depends on a lot of factors. Even at 11.5", you are losing a lot of terminal effect with .223 since it relies heavily on velocity. You can go as short as 7.5" on .223 but reliability can be less, it will be very blasty and few companies will warrant suppressors used on such short barrels.

My personal feeling is 11.5" or longer and 5.56 is the best choice (maybe 6.8 if you have the money to go exotic). Under 11.5", I like .300 because it doesn't rely so heavily on velocity and doesn't lose as much velocity when cut short, plus there tend to be less issues suppressing those shorter barrels.
 
My favorite to shoot is an 11" 7.62x39 suppressed. The .300Blk or 6.8 are great if you want to reload or don't mind the ammo cost, but I agree the 5.56 11" is the most practical starting point. Add in a .22lR conversion and you can have a lot of fun with it.
 
5.56 in 11.5" is where I would settle. I have a 7.5" AR upper and an 11.5" The 11.5" is much more useful IMVHO.

Most Suppressor MFG's will warrant their suppressors on 11.5" or longer. 5.56 is abundant and cheaper to shoot than any other caliber in the AR platform.

SWAT Magazine did an article on 5.56 on the 7.5" troy industries SBR a while a go and with the right ammo, the 7.5" barrel performed nicely.
 
I would go with a 11.5" in 5.56, and then pick up some more uppers for it of you wanted to change calibers. That way you know you have a gun that's easy (relitively) to find ammo for and will have a lot of parts available to choose from while building (one downside of the 6.8).

I personally went with a 10.5" in .300 Blk, but I've had the stamp back for several months now and STILL haven't been able to shoot it because I can't find any ammo for it :fire: maybe I'll just have to bite the bullet so to speak and buy dies and components to load for it...
 
If I was to build a sbr it would be 300 blackout, I have a 300 black out with a 16" barrel and love it.
 
I'm going with a 10.5" 300 BLK and will probably build a 7.62x40 16" upper as well. .458 SOCOM is in my future too (but probably 16").

Anyone make an 11/16x24 to .578x24 adapter?

Mike
 
So the lower is good to go?
Click to expand...

Well that depends on what lower you got. If you bought a AR-10 lower none of the recommendations are going to work :neener:

But yes, if you got a standard AR15 lower, you should be fine to register it as a SBR. I would not recommend registering a polymer lower because there have been cases of them breaking (not saying its likely, just that I wouldn't want to have to register another lower if it did happen) and there are issues of marking them with your name, city, and state (IIRC it must be done in a similar manner to the serial number, with a metal plate imbedded in the polymer).
 
Depends on a lot of factors. Even at 11.5", you are losing a lot of terminal effect with .223 since it relies heavily on velocity. You can go as short as 7.5" on .223 but reliability can be less, it will be very blasty and few companies will warrant suppressors used on such short barrels.
Click to expand...

Say what?

Incredible frag and penetration can be achieved with 77 gr SMKs or 77 Nosler Custom comp with an 11.5" or 10.5":confused:

These are both water jug fired from an 11.5... I'd have done 10.5 but I don't have a mount for the silencer on my 10.5.

aaa_zpscb56233b.gif
 
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223 is way too dependent on barrel length. I'd stick to 16+ inches for that caliber.

300 BLK and 6.8 SPC are both better calibers for short barrels.
 
If you're not a reloader, I'd go with 5.56. If you do reload then I agree there are better options that might be prohibitively expensive sans reloading. Having a really cool gun that you can't really afford to shoot is not cool, or fun. If you're both a reloader and plan on suppressing the SBR then a 300 BLK is hard to beat, IMO.

Have fun!
 
Once the lower is registered as an SBR, you can swap any barrel lengths and calibers for the upper. So the caliber/barrel length decision is not set in stone.

Furthermore, your name and address do not need to be engraved on the lower. The information can be placed on the barrel.

What I would do is engrave the name/address on all the short barrels I would want to use with the gun. Leave the lower receiver with just the factory markings. That way, you can "deregister" it and sell it as an ordinary Title I weapon later. This would actually have a greater market value than a registered SBR (which would take months in the transfer-approval process) or a lower with somebody's name engraved on it.
 
Telekinesis said:
Well that depends on what lower you got. If you bought a AR-10 lower none of the recommendations are going to work :neener:

But yes, if you got a standard AR15 lower, you should be fine to register it as a SBR. I would not recommend registering a polymer lower because there have been cases of them breaking (not saying its likely, just that I wouldn't want to have to register another lower if it did happen) and there are issues of marking them with your name, city, and state (IIRC it must be done in a similar manner to the serial number, with a metal plate imbedded in the polymer).
Click to expand...
Not true. Only the serial number needs to be on metal to meet a difficult to alter standard. Everything else can be and is on polymer. As long as your reuse the serial number, your name or trust name and town can go on polymer. Another common misunderstanding is that there is a height requirement for these markings. There is a depth requirement but only the serial number has a height requirement.

I would not recommend bothering to SBR a polymer AR15 lower but I am in the process (since Feb) of SBRing a Glock lower.

Mike
 
Let me be the odd man out and recommend 9mm. Lots of fun, cheap to shoot, and sacrifices almost no performance in a short barrel. Straight blowback operation, so you can go as short as you want. And it's perfect to suppress if you feel like doing that eventually.

Register it in every caliber you can think of, of course.
 
I am with Ryan. If your not doing long range, which you wouldn't with a setup that short, why not a pistol caliber. 9mm is OK, 10mm would be a hoot. magnum class ballistics, no recoil out of a carbine. I so want to build one as a SBR sub-gun.
 
300Blackout with a 9in or 10inch barrel would work very nice. Granted you don't mind paying a lot for 300BLK ammo right now.

If you want to stick with 223/5.56, I'd get a 10.5 or 11.5 barrel. Start your build as a AR Pistol, send in your Tax stamp, and when it arrives add your stock.
 
I've got an 8.5" 300 BLK and a 10.5" 5.56.
The 10.5" 5.56 gets more shooting time because of cheaper ammo. All of my 300 BLK ammo is my own reloads. Even as a reloader, I shoot the 5.56 more (mainly with TulAmmo), hard to beat $5.50/20.

That said, I'd take the 300 Blk hunting, but wouldn't take the longer 5.56
300 Blk from a 8.5" barrel pushes a 125gr SST bullet at 2,030 fps for 1,145 ft-lbs.
5.56 out of 10.5" barrel pushes a 64gr SP at 2,530 fps for 910 ft-lbs and that is a hot reload.
Factory 55gr XM193 hits 2,718 for 910 ft-lbs.
My standard 55gr SP w/W748 reload runs 2,450 fps for 734 ft-lbs

Both are plenty accurate enough, so just depends on what you want it for. If you don't reload, don't get a 300 Blkout.
 
I have been seriously pondering the same question.

11.5" in 5.56 is the direction I am headed

My main reasons are:
I already reload 5.56/223 ammo
Bullets are less expensive for 223
Ammo can be shared with my other 5.56 AR.
Ammo is much easier to get for the 5.56
I probably won't be doing much suppressed shooting.
 
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