[Morlock]

can a full size upper be mated to a lower w/ a cabine buffer? are there any wear/battering issues that i would have to worry about?

thanks
morlock.

[Hawkeye]

Yes, it will work just fine. No problems at all. Most of the SPR's that are in use by the military are set up this way.

[uglygun]

Just make sure you have a carbine length buffer tube combined with a carbine type buffer(a heavier M4 buffer probably being best as it would slow the action's cyclic rate).

A carbine buffer in a full length buffer tube would be baaaaaaddddddd.....

[Zak Smith]

The key factor is the length of the receiver extension tube, also known as the "buffer tube." On a rifle, this is the tube that is screwed into the lower receiver (which holds the buffer detent in place) which you can see if you remove the buttstock by unscrewing the screw in the top rear of the stock. On a carbine, the tube is part of the CAR collapsible buttstock. The receiver extension tube / buffer tube is shorter on the CAR than on the rifle. "Entry"-length stocks also use the CAR-length buffer tube.

With the CAR-length receiver extension / buffer tube, you must use a CAR recoil ("operating") spring and CAR buffer (the silver thing with the rubber bumper on one when which the bolt carrier pushes on). With the rifle-length receiver extension / buffer tube, you must use a rifle recoil spring and buffer.

The upper type does not come into play at all, except that the short M4 gas system is generally more finicky than the mid and rifle-length gas systems.

=z