HI GUYS
yesterday i clenaed my bushmaster and today i used ..
but i had a probloem...
with every mag, plastic magpul and metallic usgi, the rifle close the bolt at empty mag.
every time i shoot the last round as a "click" , with no ammo in the chamber and bolt closed...

any idea on how to fix it?
the rifle have 5 months, the magpul mags have 2 weeks
ciao
andy in italy

guys the rifle have 6 months
i fired 2500 rounds circa

now i tryed an old colt a2 and the mags work
then i :
changed bolts    no stop
swapped the upper receiver from my 16" with the 20 "   using the same lower .no stop
using another mag, i had this problem aftert the last round




the bolt dont stai opened touching the bolt face, but the middle of the bolt carrier , then when i inser the second mag and close the bolt using the mag catch, i have empty chamber


when i fire, it seem the bolt cicle 1 time and a half
when i fire i hear the recoil , like the bolt close then move rear again for a bit then close again

5 months ago i changed the buffer with the anidine recoil buffer...could it create problems?

While you were cleaning it did you accidently dry fire it with the rifle opened and dented the lower in a little?

OR

It may be short stroking and it’s catching the bolt in the wrong spot sometimes or not at all.

When you pull the charging handle does the bolt go back a lot farther then that?

well it is possible that i pull the trgger when the rifle was open...but it should not create a problem cause the hammer does not touch the bolt catch.
and about your other question...well i dont know...

i tryed the other 20" upper receiver with same results.
this upper is new, and have his hown bolt. i fired only 20 rounds , but i got same problems..
so the prblem is in the lower , not in the upper...but i dont know where....

As a couple others said on M4C.Yes that buffer could cause issues,especially with the ammo you are using.Put the lower back to its original configuration and try again.