New project time: a retro M16A1 build

Black rifles are like belly buttons, everybody's got one.  It seems like practically everyone has an AR-15 of some sort, everyone but me anyway(unless you count my 715T, which is just a 22LR 702 Plinkster in an AR shaped plastic shell).  So, I decided I should join the club.  Most ARs are lego builds, just buy the parts and slap it together, and this one won't be much different.  The big difference here is that instead of buying new parts I'm starting with a genuine Vietnam era Colt M16A1 parts kit.

My goal for this one is the "battlefield pickup" look.  These are Colt parts, and they're only original once, so I'm going to leave it looking well used.  I got my black rifle parts kit from Royal Tiger Imports on Black Friday when they were on sale.  The packaging from RTI was just plain awful.  All the parts were just thrown in the box with a single piece of bubble wrap around the buttstock.  The gas tube wore a hole in the corner of the box and the bag with all the little bits was broken open.  Consequently, a lot of the pins and little bits rattled out of the box, so I'll have to rob them from a lower parts kit I bought for another project.  After cleaning all the gunk off the parts, here's what I ended up with:

This is a Grade B kit and all in all, not too terribly rough for what it cost.  The forging codes on the upper indicate that it was made some time between '74-'82.  The parts are very well worn on the outside, but the internals look great, like the gun was carried a whole lot but seldom fired. The handguards are very rough with many cracks and missing teeth, but that's not uncommon with these early style handguards and this was a Grade B kit.  I plan to try to fix them, so we'll see how it goes.

I'm going to build it on a standard AR-15 80% lower, and I have to make it a semi-auto only rifle.  The parts kit was a machine gun, and it included all the naughty bits.  You could just throw them away and buy a standard lower parts kit, but I'm cheap, and I like the idea of using as many Colt parts as possible.  Before I even started machining the lower I had to take care of them.  Most of the naughty bits can be converted to semi-only, but one part can't be used at all.  The very first thing I did was crush the auto sear to pieces in my vice, making it completely unusable.

Next up was the hammer.  The M16 hammer has a tail on it that needs to be ground off, making it practically identical to a standard AR hammer.  Original on the left, modified on the right.

Next was the disconnector.  Like the hammer, it's got a tail on it that needs to be removed.  A few seconds with a grinder fixes it right up.

The selector lever is up next.  It's got a fin sticking up in the middle of it that needs to be ground down.  Modified in this way the selector still spins all the way around but the positions give you safe-semi-semi.

Last, the trigger needs some welding.  The AR trigger has a closed back, the M16 has an open back because of the tail on the FA selector.  The end of the trigger needs to be welded closed so that a FA disconnector will not fit.

Just changing the selector or disconnector would make it work as a semi-only rifle, but for legal reasons you need to modify all the parts so that there is no question about your intent.