Just went to slap my Bushmaster upper on my brand new AR, and the buffer tube will not fit into the stock.  It is a six position M4 type collapsible stock.  What's the problem?  Since the buffer tube won't go in, I can't put the upper on, or anything.  Thanks.

I just went on to Bushmaster site to look at the specs of their conversion  unit. It looks like your problem is that their unit is not made to work with a carbine!! Remember the carbine has a shorter buffer tube. Hence, a shorter recoil spring and buffer unit.

You might have to adapt the stock "extension" of buffer tube . You should contact Bushmaster about this problem though!!

Stuart

1.  Thank you.

2.  Shit!

I have been trying to find someone with one of these 22LR uppers....  

Can you PLEASE describe or post photos of the Bolt/Carrier used with these uppers?  Do you haveany idea if this would work with a SWD Lightning Link?

Quoted: I have been trying to find someone with one of these 22LR uppers....   Can you PLEASE describe or post photos of the Bolt/Carrier used with these uppers?  Do you haveany idea if this would work with a SWD Lightning Link?

Sorry, digital camera was stolen (I think) and I couldn't tell you much about whether it will work with a lightning link.  Instead of the gas tube there is a roller mounted perpendicular to the bolt (like a spare tire on the hood of a Land Rover) that runs the length of the charging handle.  The bolt is also mostly made of carbon fiber, and has a hole in the back, because a plastic rod sticks out of the buffer tube and slides into the bolt whenever it recoils backwards.  

Hope that helps a little.

I can help you out then....

Please see: quarterbore.com/nfa/lightninglink.html

The lightning link works by pivoting off the rear takedown lug of the AR-15 in such a way that the rear shelf of the carrier slams into the link paddle as the carrier slams home.  When the paddle is struck the paddle of the link pivots on the rear takedown lug and the forward portion of the link body trips the disconnect in a timmed and controlled way....



In order for the LL to work it requires a bolt carrier that is square cut towards the rear at the location of the rear takedown lug.  Following is a photo of three carriers with the normal Bushmaster carrier top, a SP1 carrier that will drive a LL in the middle, and an M-16 carrier on the bottom:



What I really need to know is if it is possible to mill a slot in the bottom of this 22LR bolt to provide a slot for the LL so that the bolt will look like my 9mm bolt in the following photo:



If it is possible, then this upper would run with the lightning link!