The Down Range Forum
Member Section => Tactical Rifle & Carbine => Topic started by: Big Frank on November 12, 2025, 04:31:25 AM
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The M16A2 trigger mechanism is so complicated, the military made and used slave pins to use when working on it. The slave pin is inserted and the trigger pin removed, so the trigger assembly can be removed as a unit. After any further disassembly, the slave pin can be used to hold the trigger assembly together for re-installation. The marines adopted the M16A2 before the army, so I bought the marine corp 23&P TM, Organizational And Intermediate Maintenance (Including Tools And Special Parts List) before the army made their own TM. I did Level 3 maintenance in the army, one step above unit armorers, who were one step above weapons crew/operators.
Here are a couple of pages from the TM, and a pic of 2 old trigger pins of mine, before and after modification. And a pic of 2 triggers and disconnectors, with a modified pin and an unmodified pin installed. I took multiple pictures of the new slave pin, and they all turned out bad. I don't know if it had anything to do with how shiny it is after I polished it up by spinning it against a sanding sponge with a cordless drill. Maybe it's because I held the camera one way for one pic, and rotated it 90 degrees for the other. You can tell it's been cut down to 5/8" anyway, and that's what matters most. The final length is about halfway between the grooves, so I cut it about 1/3 of the way between them, then chucked it in the drill and rotated it perpendicular to the edge of a grinding wheel running at full speed.
I seem to recall using a slave pin to hold parts of an M203 grenade launcher together during assembly, but I'm not sure. I do remember having to inspect some M203s and replace the old firing pins with a new style. The old ones were a hair too long IIRC, and could possibly pierce a primer. I think I posted before how to visually identify the old vs. new firing pins by taking the backplate off the launcher and looking at the pin, without disassembling the launcher any further. I remember using slave pins for something, and it wasn't simple M16A1 triggers. You would really need them with an M16A2 Enhanced rifle, with a 4-position selector lever. They have burst and full-auto. The Rock River Arms Star Safety Selector rolls under you thumb so easily you can hit all 4 positions without and trouble.