11.5 vs 12.5 BCM AR Pistol

AR/M4 AR Pistols & Pistol Caliber ARs
1

I am planning on building an AR pistol with a BCM upper and I will not be using a can on it so no need to go into that discussion concerning barrel length.

I currently have a 16in. Which would you guys prefer? And WHY?

-Would the 12.5 be more sloppy to use in a pistol configuration since it is heavier/longer?

-Is the flip/flash that much more obnoxious with 1 less inch?

-DOES ANYONE HAVE BALLISTICS CHART COMPARING THESE TWO LENGTHS FOR 75/77gr, 55gr, AND 62gr BULLETS?? (I will be using tap 75gr 5.56, but still interested in other gr bullets)

I really want to find out how far each one can reach out and still “fragment” reliably…

Thanks for any help!

2

I am thinking of doing the exact same thing and have the same question. For a HD pistol, I was considering the BCM 12.5" KINO. It uses a Mid length
hand guard but has a carbine gas tube.
Been wondering if that length would obviate the benefit of the pistol.Only one inch but is it that big of a deal either way??

3

All you have to do is look at the same data for SBR’s since the only REAL difference is the addition of the stock. I can hardly imagine there is going to much difference between an 11.5" and 12.5". I have both in the SBR format and though I cannot speak to the fragmentation/effectiveness issue, I can and have hit targets out to 400-500 yards. Honestly, I am not sure why you are asking about this to be honest because it will be very difficult to articulate any reasonable self defense scenarios past 50 yards.

Inside the common sense distances that you are looking at both of them will be effective. I would also suggest that you get a chrono and check the muzzle velocity of the loads you plan on using.

4

I, personally, should have been more specific. Even though only 1-2" longer, my concern was length and not fragmentation.
My defense perimeter is probably, at most, 50 yds. But, the primary purpose of the upcoming pistol is HD withmaybe a max of 10 yds.
But, my concern was mobility in the home and I solved that poser.
Thanks for your reply
Be well

5

I have the BCM 12.5 for my pistol upper. Had the 11.5 been available thhat is what I would have gotten instead.
For the purpose of owning a short nimble little carbine/pistol either will serve you fine, but the shorter barrel may be just a shade handier.
With that said, I find the whole system pretty darn handy.

6

Thanks averageman for an above average answer :slight_smile:
I am awaiting a reply from BCM and will go with the 11.5" upper. I’ll put a Magpul MOE handguard around it. and try to keep the rest simple.
Be well.

7

Actually my response was direct to the OP since this is his thread. If anyone says that they can discern the difference between an 11.5 or 12.5" when it comes to handling or feel I guess I will just have to laugh. If my two uppers weren’t different configurations I wouldnt be able to tell them apart.

8

Not sure what your issue is, but this isn’t your thread. I was responding to the OP.

Sorry if I don’t agree with you on the subject of 1". But since I have had a number of years and rounds through both in the SBR format the only place the 1" makes a difference is on the big screen.

If you have some other issue with what I said the formulate a coherent response and PM it rather than hijacking this thread.

9

OP - I have a 16" BCM middy and wanted to build a pistol - did all the research and concluded that 11.5" was the way to go over any length for a 556 pistol. It is a perfect balance of compactness, reliability and performance. Paul B at BCM wrote an interesting article about the advantages of 11.5" over 10.5" - its a good read if you can dig it up. Went with a lightweight profile and could not be happier. Added an SB15 and it is the most versatile AR I’ve owned.

10

I am not the OP but had the same question.In the aricle written about the11.5" BBL, the word balance came up quite a few times. I hope my end product looks as good as yours.
Be well

11

11.5 BCM BFH here. I’ve only shot it at around 25 yards and was utterly shocked how accurate it was. I’ve read some people having feeding issues with shorter than 10.5 so I went with the 11.5 and have had 0 issues. I see no reason to to go 12.5. The accuracy in a 11.5 is more than enough. Also it is very easy to control. Very little flash and very manageable recoil.

Shameless plug: this upper is also for sale in the marketplace.

12

Got her done:

13

One of my rifles is a 11 1/2 in barrel (6in FH) and 12 1/2 in BCM upper pistol. I’ve shot rifle 300 meters no issues on accuracy. Went with 12 1/5 BCM upper pistol with intentions to SBR it later it will out shoot my ability for accuracy as a hand gun. Mine is about a mirror of docLRRP’s I’ve had mine set up the same for about 4 years it handles as any 6 pound handgun would.

14

I have an 11.5 BCM upper on a pistol

I chose to go with the 11.5 over anything shorter because the 11.5 offered more ballistic advantage than anything shorter.

15

I used an 11.5" BCM upper. I have been asked about the blue FH.
It is from the X300U with a blue filter, that I left on…
A few more degrees upwards and to the range she goes along with a couple of new BCM 14.5" middy builds.
BTW, the balance on the 11.5" is just superb.
Be well.

16

I have had both 11.5 and 10.5 and could not tell much of a difference. that being said I would not g over 11.5 because the idea is to be short

17

Do you notice any advantage to the PWS CQB vs A2 flashhider?

18

Can always throw it at someone when your out of ammo… would probably be more efficent than those strobe light thingys that just came out ha ha.

19

I would go no shorter than 11.5 in. in 5.56. My BCM 11.5 ran perfectly. (traded it for something else because I didn’t want the fixed FSB)

If I wanted a longer gun I would (did) move up to a 14.5 with pinned flash hider.

20

I wasn’t willing to go shorter that 11.5 and when the 12.5 was available when I had the urge to build a pistol that’s what I went with.
It doesn’t seem to make any difference in it’s abilities or shortcommings.