Question about upper interchangeability
I currently own a BCM carbine length rifle.
If I were to purchase a BCM mid-length upper, are there any interchangeability issues I can expect, or should the upper plug right in and cycle just like the one that came with the rifle?
Do I need to replace the buffer?
Do I need to tweak anything?
The reason I ask is that years ago I owned two identical Colts, and out of curiosity I swapped the complete uppers with each other. The rifles believe it or not suddenly started cycling unreliably until I swapped the uppers back to their original rifle, leaving me to believe there was some little tweak that needed to be made.