hey all, I'm a former 45B and worked at the ordnance school teaching the M2 class, so I know Ma quite well....but I have a question:

The SA plate is thicker than the FA plate.......that way FA parts will not fit inside the "box".......

no shit. ok then that makes perfect sense. thanks!

The term used to describe the thicker blocking area on the side plate is "denial island."



So it's not just a counseling retreat you attend with your significant other.

OK, last lame joke of the day. No promises.

haha I love that one. My friend was just asking me the other day why the inside of his AR15 looked different than my M16....

Denial Island!

u guys are such kidders haha

That might not be the only way to get a semi M2 design, but it does form the basis of most of the approved US beltfed semi conversions currently out there.

ATF requires that the receiver of a semi version of a machinegun be different from the machinegun version in a way which precludes easy installation of unmodified full auto parts, but judges each different firearm design individually.

On most of these belt feds, the ATF arbitrarily decided that the right side plate was the "firearm frame or receiver" because that was where the US Army Ordnance Dept. decided to stamp them with serial numbers and model information, so it is the right side plate of most semi belt feds which has to be different from the machinegun right side plate.

There have been semi side plate designs which used blocking pins or riveted and welded-in blocks to accomplish the purpose of preventing installation of full auto fire control components in addition to the more common denial island.  It's just that the denial island is really, really inexpensive and easy to do when you're making side plates from scratch by conventional or CNC milling.

thanks for all of that.

The semi bolts are modified by first altering them to no longer take a full auto sear and trigger, then machining them to pass the blocking bars or denial island.  Most designs also modify the barrel extension and lock frame, but the important part is converting the bolt to no longer take a GI full auto sear, and then producing a semi-only sear/trigger design to fit the semi bolt.

okk. so bolt it is. makes sense. i will have to look them up. id like to see a semi sear. thanks!