.450 Bushmaster with standard lower question

[AGarbers]

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?

 

[spainy79]

Didn't change a thing. Exact same components in my 5.56 lower as the 450.

 

[djl02]

I think you'll be fine, but if you need a dif spring ,I have 3 diff ones , you might try, you in southern Indiana?

 

[spainy79]

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.

 

[DEC]

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.

 

[hawg9259]

all the same with mine, bushmaster upper on a rock river lower,