Considering a new SBR build in 10MM AR-15

[Lennyjoe]

Im considering building another SBR AR-15, this time in 10MM so I can run a 200 gr bullet just under subsonic with a suppressor but an having a hard time justifying the build since I already have one in .300 Blackout.

Outside of the whole “variety is the spice of life”, why should I spend the $$ building one. I’m a reloaded so building the perfect round for the rifle would be fun as well.

Thoughts?

 

[Havok7416]

If you have to ask, I would say it's probably not worth the effort. You already have your bases covered with the Blackout, so short of the previously mentioned "just because" I personally wouldn't. YMMV

 

[Ryanxia]

Do it because this is America and a 10mm SBR is epic! Then you can carry around a 10mm Glock and use same mags maybe?

 

[MachIVshooter]

Why not just do it as a pistol with the SB15PDW stock, save yourself the $200 and hassles of SBR interstate transport?

As for 10mm, I'm a huge fan of the round. I built an upper in 10mm, only to discover that I just couldn't get enough gas with a pistol length system. Solution? Ream it out to 10mm magnum I'm still working out magazines that will feed reliably with more than 9 or 10 rounds in them, but the plan is to swage 300 gr JHPs to run at 1,050 FPS. Quite a lot more thump than a .300 blk without the magazine capacity handicap of stuff like .458 Socom.

 

[Gtscotty]

I'd like to do a .40 S&W carbine to get the same effect. I'm not sure that the bigger 10mm case buys you anything if you're just trying to shoot 200gr bullets subsonic, but different strokes for different folks.

The draw of a suppressed PCC over a .300 BLK for me is:

1: Cheap bullets designed to reliably expand @ subsonic velocities.

2. Ease of reloading: no adding lube, removing lube, trimming, etc. I just tumble my (usually free) brass and send them back through the carbide dies until they get too short, then I chunk them. It's literally easier and quicker for me to bang out 100rds of 9mm/.40 on my progressive than it is for me to drive to the store and buy loaded ammo.

I do .223 on the progressive as well, but there are a few extra steps.

 

[Lennyjoe]

Figured since I’ll have to file for the suppressor I might as well do the SBR as well.

 

[CLP]

I built a 9mm AR because:
1. Parts are cheap and plentiful and I might not be able to build one again several years from now.
2. Bought the CMMG 9mm dedicated lower on sale at Brownell's.
3. I didn't have any pistol caliber rifles.
4. Brownell's carries 20 and 32 round mags that work flawlessly.
5. Ammo is cheap to buy and cheaper to load.
6. The MAIN reason- because of its blowback operation I can shoot cast boolits all day in this thing and not worry about any gas tubes getting gunked up. I'm not sure if this applies to 10mmg Auto but I think it probably does.

 

[Sebastian the Ibis]

If you want to go subsonic I don't see what 10mm offers over .40. Personally, I'd go with 9mm. Pistol caliber ARs always seem to be finicky and need some tinkering, there are more 9mm options and information out there.

 

[Lennyjoe]

Initial thoughts, pushing a heavier handgun bullet at a higher velocity. More ft lbs of energy staying under the speed of sound. Pushing a 200 gr JHP at 1075 FPS is much better than a 147 @ 900 FPS.

But, I already have a .300 Blackout SBR pushing a 208 gr 1089 FPS out of a suppressed 10” barrel so why spend the $ on a pistol caliber?

 

[Ryanxia]

AND if you had a 10mm carbine, you could always do an alternate setup for 9x25 dillon
https://en.wikipedia.org/wiki/9×25mm_Dillon

 

[Dentite]

Initial thoughts, pushing a heavier handgun bullet at a higher velocity. More ft lbs of energy staying under the speed of sound. Pushing a 200 gr JHP at 1075 FPS is much better than a 147 @ 900 FPS.

But, I already have a .300 Blackout SBR pushing a 208 gr 1089 FPS out of a suppressed 10” barrel so why spend the $ on a pistol caliber?

I think you summed it up there. You already have an SBR that shoots a ~200 grain bullet at the same speed. So would you spend $1k or more for another SBR that does the same thing but with a less aerodynamic bullet?

I went through the same thing but going the other way. I wanted a SBR in either 9mm or .300 BLK to shoot suppressed. I ended up going with 9mm because I'm already set up to reload it on my Dillon, already have dies, cases, and it's faster and easier for me to reload it.

 

[JWF III]

Initial thoughts, pushing a heavier handgun bullet at a higher velocity. More ft lbs of energy staying under the speed of sound. Pushing a 200 gr JHP at 1075 FPS is much better than a 147 @ 900 FPS.

But, I already have a .300 Blackout SBR pushing a 208 gr 1089 FPS out of a suppressed 10” barrel so why spend the $ on a pistol caliber?

I’ve been wrestling with the same idea. The reason, for me, is bullets that are designed to expand at the lower velocities. That 208 ga from the BO is a target bullet. Or a rifle bullet designed for, more than, double the velocity that the BO is pushing it at.

That 200 ga from the 10 mm is right in it’s designed range. Bad medicine for deer in a reasonable range. Here in GA it’s more because I want to try it at least once, now that suppressors are now hunting legal. But seeing that you are in Ohio, you have, sort of, the same reasoning. 10 mm is legal, where as the bottlenecked BO is not. (I don’t know the OH laws regarding hunting w/ an SBR or suppressor.)

Wyman

ETA- The new Hornady Subsonic hunting load/bullet may solve the problem for me though.

 

[wally]

I built a Glock mag 9mm SBR and really liked it, so I built a .40 S&W upper for it. Liked it enough that I built a pistol lower as well, all the post election $30 stripped lower sales made this pretty compelling

If you are planning to stay sub-sonic I don't see what 10mm adds over .40S&W except extra expense and hassle. I've read the 10mm is too much for blowback, but not enough gas for "normal" AR operation so you may be in for a challenging build.

Olympic used to at least catalog a 10mm AR rifle, but it used proprietary mags and they have gone belly up.