I just ordered a 450 Bushmaster upper from Franklin Armory. What do I need to do to use my existing lower? Some articles I have read claim I need to change out the buffer spring and perhaps a few other items. Other articles claim I don't need to change anything.
Any experience on this?
I shouldn't have said "exact same". I am running a Timney in the 450 and stock triggers in the 5.56's. I hate the stock triggers now after using the Timney.
I have now ran my Bushmaster 450BM on three different lowers and no issues. All had standard buffers and springs. One had a RR 2 stage trigger, one had a light hammer and JP spring, and one has the standard AR trigger group. Zero issues in any of them and the upper.