Do you think I should replace the BCG? Is it really worth it? I didn’t realize there was anything wrong with my gun until I read a thread where people were looking at various BCGs. Apparantly, I don’t have the LMT one, which is better. 
I am going to the Pat Rogers carbine course in Dec. Should I fix this thing? What all should I replace??
Give Grant at G& R Tactical a call, see if he will stake your carrier for you and sell you a Crane o-ring extractor upgrade kit. You might also want to buy and extra bolt while you’re at it because you don’t want to be “that guy” if your carbine goes down at Pat’s class. Give Grant a call; he will take care of you.
P7- I have 3 M&P15’s. Two are the older, Stag built version- one is the newer S&W built version.
Of the two older ones, one is properly staked, and one is not. Both have the older, 4 coil extractor spring and blue insert.
We ran one of the older ones in 3 classes. During one it became sluggish (at 3000= rounds). We field cleaned it (first time cleaned) and properly lubed it. Still sluggish, so we replaced the buffer spring. It runs fine.
When i get a little time i’ll stake the one gas key and replace the extractor springs/ inserts.
Bottom line is this. Shoot it. If you can/ want to send it to Grant he can hook you up. If not. we can do this at class.
Hope this helps.
I wouldn’t replace the carrier (it is good to have a spare GTG carrier though). When I restake these older CMT carriers which are really just witness marked staked from the top. I pull the gas key off and remove the finish on the bottom side of the key on an Arkansas stone so that there’s a better seal when it’s on the carrier. I use two brand new screws and torque to 55in lbs and stake with a MOACKS and counterstake with a P-MOACKS.
If you have a M&P15-T you may want to ‘dimple’ the barrel for the the rear set screw on the lo-pro gas block, I’ve had to fix many of these (on M&P15-Ts) because the gas block had moved.
I always take at least a spare bolt/carrier assembly (complete with firing pin etc.) with me anytime I go shooting an AR, and especially at classes.
So, since you need to buy a new one anyway 
, I’d pick up one of Grant’s FN Contracted BCGs and stick that in the gun, and use the one you have as a spare. You can stake the key and replace the spring/insert as time permits.
Not sure which PR class you’re going to in December, but if it’s the one in Florida I will be there with my staking tool and can fix you up in about 5 minutes. If not, I’m sure that Pat or someone else will have the same tool at the other December class. Either way, Pat usually travels with a good supply of spring/insert kits and he can fix you up with those parts.
GotM4- solid info there. Is the factory aware of this?
Thanks guys. I appreciate all the advice. 
I’ve told Ernest Langdon (S&Ws Federal LE/Gov’t sales) and our civilian regular S&W rep about this. They both say the rifles are now in-house. So hopefully they’ll fix it in production.
Got it. So this was on the old rifles- the Stag ones?
The head of LE sales states that the in house are at ser# 50k/ above. have you seen them?
If so, problem solved/ not?
I have talked to my regional rep at S&W as well about this as well.
C4
It’s on both old and new M&P15-Ts.
grrrrrr…Thanks. I’m doing an article on 3 M&P’s over a specicic time frame. I will look for this as a potential problem.
Good 411~
Gents, re: recent M&Ps- In June I happened upon a batch of M&P15-As delivered to a LE customer. The several I looked at from the group were all positively staked at the carrier key and castle nut, had the proper extractor spring assembly, and appeared to be assembled well otherwise. I was rather impressed.
Being cynical, I had speculated that they had received some extra TLC in production for the benefit of an end-user that could drive more sales, or negatively impact them. I was told that those coming in recently were all like that.
Perhaps someone is listening?
The sweet deal that was inked also evidenced a sincere desire by S&W to get their offering into some hands.
I made a number of suggestions to them when this was still in the nascent stages.
M4 feedramps
1/7 twis
Proper staking
Proper spring/ insert
And so forth
They lost in the begining, probably because while the LE guys are very GTG, the company is lost in space and wanting to deal with casual buyers rather then regain the cop market.
Switched on civilian shooters will buy a good gun.
Switched on cops won’t buy a hobby gun (administrators and bean counters excluded)
I have been in touch with them on a regular basis. S&W is listening.
Whew…