SBR...caliber choice

automan71 · Sep 30, 2015

Thinking of an SBR on an AR platform... Want something handy I can put my can on, and shoot stuff (paper, steel, varmints/pests, terrorists

) maybe out to 100-150yds. My picks, so far, are 9mm, 223, and 300blk. I will be shooting this nearly 100% through the can, mostly supersonic.

Some pros and cons I've thought about...

9mm...I'm super invested in 9mm ammo, cheap to plink with, quietest (subs or supers), some say finicky to make run correctly, dedicated lower receiver, not as much power at 100yds as the other two

223...reasonably priced ammo, accurate (correct barrel twist for most bullets), more power than 9mm, not as efficient through short barrels, more gas blast to the shooter when using suppressor, more pressure on can bc of short barrel

300blk....ammo expensive compared to the other two above, efficient from short barrels, quieter than 223, able to shoot subsonic loads easier than 223, accuracy not as great (what i've read) due too fast twist barrels geared towards subs, more power than both above

I have no experience w/ the 300, only experienced 223 through carbines, and 9mm only through pistols.
I like the idea of the 9mm for the cheapness of the ammo, but seems like quite an expense for not much performance over a pistol. ??

Looking for others experiences/thoughts, that have been down this road. What did you choose? Why?

kingfhb · Sep 30, 2015

Hmmm.... I would just compromise on the two and go with the .223/5.56 if you plan on going out to 100-150yds with an SBR. I would have said go with the 9mm otherwise.

DAVE_M · Sep 30, 2015

Either 9mm, because you are "super invested," or 300BLK, because it makes a better SBR.

Honestly, when you say SBR, are you asking about a 14.5", 12", 10", or <10" SBR?

If you're going the 10" route, then definitely go for 300BLK.
If you're going the sub 10" route, 9mm would be fun.
If you're just going the sub 16" route, to make a short battle rifle, then .223/5.56 is good to go.

automan71 · Sep 30, 2015

Dave...I was thinking 7-10" 9mm or 300blk and probably 10-12" for the 223/5.56 bc I think that's the limit on my suppressor for this round

DAVE_M · Sep 30, 2015

automan71 said:
Dave...I was thinking 7-10" 9mm or 300blk and probably 10-12" for the 223/5.56 bc I think that's the limit on my suppressor for this round

Then my choice would be 12" 300BLK. If you want some solid feedback on a 300BLK SBR, contact Jasarii (Will). He's a member here and has experience with that rifle.

slogoat · Sep 30, 2015

My vote goes to 223/5.56, and if you want to shoot subs build a super short 22lr upper to pin on it. My 4.5 inch 22 upper is probably the most used plinker I have. 9mm is really fun too, but given the options you listed, I'd start* with the 223.

*This may be your first, but it won't be your last! lol

JCcypress · Sep 30, 2015

automan71 said:
...maybe out to 100-150yds. ... I will be shooting this nearly 100% through the can, mostly supersonic.

I think this answers the question. I've been shooting a 10.5" 5.56 (mostly suppressed) almost exclusively for the past couple of years. Plinking, training, hog hunting, etc. and I have no complaints.

Ammo can be had for under .25 per round. I have a full brake on it to take some of the punch off the can, but that means that shooting unsuppressed is LOUD. I use a 1-4x variable optic and can hit hogs within 200 yards on the move. You won't be able to do that with 9mm.

I have an almost identical set-up in 300 BLK, and regrettably never shoot it. It's a great round and may give better terminal ballistics, but the price per round has me grabbing the 5.56 over it every time. If you can swing the ammo cost, the 300 BLK is your friend. I just shoot too much to justify it. If I want to go BIG and precise, I'll bring my AR-10.

ETA: I hear more guys talking about 12.5" in 5.56 lately. Better ballistics and easier on the can. My personal preference remains 10.5" or 10.3" as I like the MK18 profile.

But, as they say, "There are many ways to the mountain top."

HogHunter1203 · Sep 30, 2015

SBR your lower receiver with a 300blk 8-10" upper. Now you can shoot suppressed subsonic and supersonic 300blk without giving up much in the super velocity area. Then if you want just notify the ATF of a caliber addition and get a 223/556 pistol upper to slap on it.

Also the 30 cal cans like AAC SDN6 or SiCo equivalent are rated for 556 as well. Save a bit on the can end by having 1 for both jobs.

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JCcypress · Sep 30, 2015

^ Truth. Best of both worlds.

rcm192 · Sep 30, 2015

HogHunter1203 said:
SBR your lower receiver with a 300blk 8-10" upper. Now you can shoot suppressed subsonic and supersonic 300blk without giving up much in the super velocity area. Then if you want just notify the ATF of a caliber addition and get a 223/556 pistol upper to slap on it.

Also the 30 cal cans like AAC SDN6 or SiCo equivalent are rated for 556 as well. Save a bit on the can end by having 1 for both jobs.

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I have a pending form1 7.5" sbr candidate in 5.56. If I want to slap a 300blk or which ever other caliber upper on for temporary use must I notify the ATF of a caliber addition?

HogHunter1203 · Sep 30, 2015

My understanding is, technically and legally yes. I don't remember if there is a specific form to submit or if you just have to send them a letter notifying them of the change. What I have been told by ATF officials is you should not try to SBR a lower in multiple calibers a at the same time. They want to see 1 designated caliber on the form 1.

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Barney88PDC · Sep 30, 2015

10.5" 5.56 with variable gas block. Minimum 8 twist.

cajun 22 · Sep 30, 2015

You do not have to notify the ATF of any change unless it is permanent. You just register the lower with the upper you will probably shoot the most. As long as you own the parts to put it in the original registered configuration you do not have to notify them when you put another upper on it or to travel with it, other than the 5320.20. If you sell or change the original configuration then you would write them to tell them of the change. I have five uppers for one registered lower and swap them out all of the time.

This is directly from an ATF field agent.

OP I vote 5.56/223 in 10-12 in.

HogHunter1203 · Sep 30, 2015

I know several folks who do the same and have never had an issue. However my information came from an ATF agent as well. To avoid the possibility of trouble, I'd check the law itself for clarification. You never know when a not-completely-informed LE officer or hard nosed ATF agent will decide to be a punk and give you a hard time about it.

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slogoat · Sep 30, 2015

Notification of temp changes may not be a requirement now, but I bet it will be if everyone starts emailing the ATF for clarification. Lol

spec50trout · Sep 30, 2015

6.8 SPC AR 15 Performance 12.5" midlength or Bison Armory 11.5" carbine length would be my choice in barrels. Many choices in ammo from plinking to hunting. Yes, I'm biased!

InterstateGuns · Sep 30, 2015

slogoat said:
Notification of temp changes may not be a requirement now, but I bet it will be if everyone starts emailing the ATF for clarification. Lol

Exactly. Don't poke the bear.

SpeedRacer · Sep 30, 2015

I think 5.56 is the obvious choice given the criteria. You can always add more uppers later to scratch whatever itches arise, unlike a 9mm build which is very limited. Also, I think there are much better platforms than an AR for a 9mm SBR (Sig MPX, etc).

I wouldn't go less than 10.5", personally I like an 11.5" 5.56. A little smoother cycling and a little less wear and tear on your can compared to the 10.5", but still short enough.

automan71 · Sep 30, 2015

Good info guys! I appreciate all of the input. At this point, 5.56 is in the lead!

Double checked w/ Silencerco...I'm good to 10" with the 5.56

noob · Sep 30, 2015

If I can only have ONE, then I would go with a 10.5 inch 5.56 SBR, which ammo is cheaper and easier to come by, and it can reach out to 200+ yards easy. (I shoot my 10.5 inch noveske at a 8 inch plate @200yard without issue).

THEN after you get that, you can get a cheap 8-10 inch 300blk upper when you can afford it later down the road, and if you REALLY wanna spend the money, you can also buy a 9mm mag block, and 9mm upper.

I happen to have all 3 in SBR's with separate lowers, but I Think pretty much we all fall into that NFA trap, where once you get one, they multiply quick.

And uppers can be had REAL cheap lately, 3-400 bucks is not uncommon, the 5.56 and 300blk will share the same mags and BCG.

Or you can get a Sig MCX which can change calibers quickly.

SBR...caliber choice

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