kNS anti roll pins. is this really needed. also, if i buy an LMT bcg for my bushmaster, will it drop in without any mods. whats the best buffer to use with an m4 profile bushmaster. i know there are different sizes. thanks
KNS pins are not needed. But I like them for serving as cheap bit of “piece of mind”. Yes the LMT BCG will drop in without issue. “H” buffer should be all you need.
If your gun runs now with its current buffer leave it. I would however stake the BC key.
KNS pins must be stopped.
While you are at it, buy a “Field” headspace gage from Bushmaster and ensure that you have a proper headspace if you are replacing the bolt.
KNS pins aren’t needed if the lower is properly assembled. I use them for a consistent trigger pull.
It’s always a good idea to check for excessive headspace using a USGI FIELD headspace gauge 1.4730" when trying a bolt in a barrel where they previously weren’t used together. If the bolt closes on that FIELD gauge don’t shoot the rifle and try another bolt.
For a buffer in a Bushmaster barrel I recommend a H buffer.