Using an AAC 51T mount with 11.5 inch barrel

General Firearms NFA
1

Is this possible if you use a short clamp on gas block like the DD version? Thus allowing the use of the AAC SPR-M4?

2

Edit: I have a 51T Brakeout mount on my 10.5" SBR. If you are using the AAC blackout or brakeout, yes, it should fit, but I’m not sure if you can, or if I would recommend using the SPR/M4 suppressor on that mount. If you are talking about the MITER mount for an SPR/M4, no, you need 12.5" minimum barrel length for that mount to fit. If you’re using that barrel length, get the Blackout or Brakeout and get an M4-2000.

3

Not sure what you are asking, but to clarify what is needed for either mount:

  1. You will need about an inch in front of the rail to use either the 51T Blackout, Brakeout, or Brake for use with the AAC M4200 or Mini4.

  2. You will need at least 2.5" of clearance in front of the rail to use the 51T MITER mount for use with the AAC SPR/M4

4

I have the SPR-M4 and the 51T miter mount, considering the 11.5" length for an SBR, and measured a friends 11.5" yesterday. It would appear that by using a small clamp on style Daniel Defense gas block that adequate clearance to the gas block would be available. I understand that the silencer itself would either have to fit under the handguard, or not go under it at all.

Thanks for the replies.

Is anyone currently running a mirror image of this setup?

5

Good luck. Let us know how it goes. I’m curious to see if you can get it to fit correctly. As I stated in my last post, AAC states that you need a 12.5" barrel (using a carbine length gas system) to fit the MITER, and as Ironman8 stated, 2.5" of barrel clearance for the mount to fit over the barrel. I’m fairly certain that regardless of gas block profile, you’re going to run out of barrel. If you can get it to fit, I’d be interested in seeing the set-up though.

6

You missed my point…between the gas block and the muzzle of an 11.5" barrel, you will have 4" of clearance which means the Miter Flashider will have 1-1.5" of clearance between the back of the mount and the gas block/port.

My point that you missed is that your problem won’t be running into the gas block, but will be clearance for your rail. The max lenth rail you can run would be about 9" to not interfere with the suppressor.

To my knowledge, nobody runs the SPR/M4 or any other AAC QD can UNDER a rail due to not being able to manipulate the unlocking mechanism when taking the can off…SO that leads me back to my point that it is not the gas block that you will run into, but the RAIL that you need the clearance for the SPR/M4…

Good luck!

7

Since I have had the SPR-M4 for a while and use it on other rifles and carbines I understand the unlocking access issue, thank you.

It would appear that a 9" Troy would not allow the AAC unit to fit underneath it, so more likely a 7" freefloat, one that would come to the receiver side of the gas block and some gap between the handguard and the silencer would be likely.

Once again thanks for the inputs.

8

:jester: Got it. Thanks for the clarification. Sorry for making the water muddy on this one. I learned something new today.

9

That actually wasn’t directed at you lol…but glad it helped you out as well…