Carbine to midlength buffer

[sabrefan]

I swapped the complete lowers of a carbine and midlength. Should I swap the buffers?

[Joeywhat]

How does it shoot? If it's not working, go to a different buffer to see if it fixes the issue. If it does work...don't do anything.

[mkmckinley]

Are the buffers different weights (i.e. standard with no markings, H, H etc)? If so, I would generally put the heavier buffer with the shorter gas system all things being equal. Either way it's not going to make a huge difference if everything was working well before you swapped the uppers. If you had an extra weight buffer to try to counteract an overgassed carbine length system I'd keep that buffer with the carbine upper.

[Failure2Stop]

I have had midlength uppers from very good companies that would not lock-back on an empty pmag with Federal XM193 when using H or H2 buffers in a carbine RE. So I generally advise to start with a normal CAR buffer and then experiment with heavier buffers and cheap ammo.