Originally Posted By: iowayotehunter76The mag is a great lakes firearms. Ammo is hornady black 250 grain ftx. Buffer I am unsure of. It is RRA standard A2 stock. I bought it as a complete rifle for my first AR. It was predator pursuit model with a 20 inch SS barrel, if that helps. I dropped the lower and put the 450 on it hoping to switch back and forth.
so a standard a2 buffer is usually right around 5.9 oz. the standard buffer spring is fine for your application. compared to a standard carbine buffer at 3oz.. you're probably in ok territory.
id have to guess you're dealing with a mag related issue.
order up one of the ar stoner ones as a spare and you'll know for sure, unless you know someone else who has one to test with.
https://www.midwayusa.com/product/761181...ess-steel-black
if you do find out its not mag related and you're dealing with an overgassing issue, you have a couple options.
1) xh buffer from slash's - they tip the scales at a whopping 11oz, but come with a cost of about $125. I've got one in my ar-308 and they're nice, but it was spendy option. it also may or may not work well with your factory upper. should be ok... but i cant guarantee it wouldnt require swapping buffers when you switch uppers.
2) adjustable gas block - you can cure many evils with one of these. but again you're looking around $100 price point for a quality one. If you plan to suppress this rifle in the future this will be *the* way to go. just something to consider.
3) head over to the 450 bushmaster forum and order a bolt carrier slug from Hoot (search CCWS). its a lead bar that you epxoy into the rear of your BCG and adds almost 4oz to the carrier which gets you close to the XH buffer weight at about 10% of the cost ( i think i paid like $15 for mine?) Tubb's used to make something similar, but they dont seem to be available anymore.
this is from when i did mine. and yes you can still get the firing pin out to take the bcg apart for cleaning.
add some jb weld after a full degreasing of the bcg
the rear view
HTH