These guns were spec'd for "MRBS" Mean Rounds Between Stoppages" These pistols were engineered for extreme reliability, durability. This firearm designed around ruggedness has testing that has exceeded 11,000 rounds and one "M" gun going 30,000 rounds before RSA replacement. During testing phase 6 Glock M guns went 120,000 rounds without stoppage with Speer Lawman Ammunition. That's 20,000 rounds per firearm with zero stoppages. Some of the "M" features are, but not limited to the following:
Enhanced Locking Block
NDLC Slide Marked 19M
NDLC Barrel Marked on top "M" per Contract featuring Enhanced Marksman Barrel.
NDLC Enhanced Trigger-bar
NDLC "." Connector
NDLC Proprietary Spec Cruciform (33588)
Ameriglo "Agent" U notch Ameriglo Night Sights.
Ambidextrous Extended Slide Stop Lever.
30274 Ejector TMH 33854
(3) OEM 15 Round Magazines.