I want to install a FRT 15 trigger in my M&P 15 and it requires a full auto BCG. I'd also like to know what the stock buffer is, I'm told l should use an H3? Thanks.

My M&P15A (purchased new about a dozen years ago) did not come with a FA BCG (but the one it came with was properly staked). IIRC it came with an H buffer. I replaced the BCG with a FA the buffer with an H2, and the trigger with a Geissele SSA.

I have a Sport II manufactured a couple years ago and it also does not have the M16/FA carrier.

I have another AR I built that does have the M16/FA carrier.

I cannot seem to escape my skepticism as to how big a deal that really is. I mean sticking a slightly heavier buffer in there accomplishes pretty much the same thing. Or so it would certainly seem.

This might help

It has to do with how the FRT-15 works. The hammer and trigger are reset by the BCG going back, but they need to be locked until the the bolt is fully forward again and back in battery.

It's the bottom of the BCG that engages the lever on the FRT-15 that causes the trigger and hammer to unlock, where the bottom of a semi auto BCG is too short to engage the lever.

As far as what buffer you need, the OP will have to do some testing to find what works best for his rifle.

You might want to hold off on obtaining and installing that forced reset trigger right now, until this matter is sorted out.

Leaked Email: The ATF Is Planning On Seizing Items Starting Tomorrow - YouTube


South Florida Federally Licensed Gun Shop Owner and Employee Charged with Illegal Sale of Unregistered Fully Automatic Short-Barreled Rifles and Other Firearms | USAO-SDFL | Department of Justice

Pictures provided at the link in the above document, along with the verbiage of the document, certainly appear to imply that ATF is now asserting that forced reset triggers constitute machine guns.

Right. I did know that, but I've seen people talk about how the extra mass tames the action.


I have an M16/Full Auto BCG in my Aero build actually.