Those familiar with the M16/M4/AR15 will be surprised to find two springs and detents under the M&P15-22 grip. The springs will be pretty obvious but the little detents can fall out undetected and they take a sharp eye to find after they've bounced across your basement floor. (Who, me? )

The M16's rear takedown pin spring and detent are secured by the stock or receiver end plate on the carbine versions, hence the surprise many of us get removing the M&P15-22 grip.

-- Chuck