Quarterbore.Net Forums

opticalc · #1 02-18-2008, 10:40 AM

I have a relatively new Colt LE6921 SBR where the receiver is not marked 6921 but rather marked "M4LE", and it came with a full auto M16 BCG, but not M16 fire/trigger control parts. I'm planning on getting a rLL and a KNS protector and some for of select fire kit to go along with it. For my upper's rLL compatibility I'm planning on going with the DPMS bolt carrier route since there are many reports of that working so well. But for lower compatibility I am wondering after reading the quarterbore article how much work it will take to get my particular lower to click with the rLL.

Can anyone comment on how well my lower will work

Quarterbore · #2 02-19-2008, 10:57 AM

Can you take some photos of the internals of your lower (obviously without the upper in the way)?

As for worying about a particular lower and using that with the link, that is really backwards almost as bad as buying tires and then looking for a car that fits them. Buy the rLL and if the Colt does not work, either modify the lower so it will work or buy a Bushmaster lower that will work without modification.

opticalc · #3 02-21-2008, 11:47 AM

I've shrunk them down, they dont look so bad now.

Quarterbore · #4 02-21-2008, 01:24 PM

My reply was lost in the server move... Your lower does have a sear block so for this lower to be used with the LL you will need to have it milled out to "Bushmaster Specs" to use this with the link.

Personally, I would just buy a Bushmaster lower and use that as it will work without modifications (well except for the carrier).

opticalc · #5 02-22-2008, 06:00 PM

is that a m16 hammer in my lower? if so i wonder how many other parts are m16. i do see that big sear block though...

Quarterbore · #6 02-23-2008, 11:52 AM

No, that is an AR-15 hammer. Note the notch in the front of the hammer and you do not have the spir at the rear.

http://www.quarterbore.com/nfa/registeredreceiver.htm

opticalc · #7 02-25-2008, 01:16 PM

OK, I had been referring to diagrams on another site apparently have the m16/ar15 labels swapped. Thanks for the link.

1 more question: is the BCG or just carrier for a 6.8mm SPC upper the same as the BCG for a 5.56 upper or carrier?

Quarterbore · #8 02-25-2008, 02:11 PM

I believe the only difference is the bolt. Obviously the 5.56 and 6.8 have different size case heads....