S&W M&P: Slide releases when mag is inserted.

[Ring]

my USP and g27 both do it if you hit it hard

[nickdrak]

"R.T.F.M."

Page 16 of my M&P manual states:

"WARNING: DO NOT USE EXCESSIVE UPWARD FORCE
WHEN INSERTING A LOADED MAGAZINE INTO THE
PISTOL. EXCESSIVE UPWARD FORCE COULD CAUSE
THE SLIDE TO MOVE FORWARD, CHAMBERING A ROUND AND
MAKING THE PISTOL READY TO FIRE."