Chapter 7

Magwell and Bottom Operations

Finally got around to machining out the lower portion of the magwell and the bottom plane operations. I was pretty antsy to see how well the magwell seams matched up and to see how smooth I could get the walls of the magwell. The rest of the bottom plane was dirt simple - just 2 slots, a milled flat, and a stepped hole for the selector detent. I once again used a solid carbide 3/8" end mill which provided excellent wall finish as well as zero deflection - definitely going to invest in some more carbide tooling. Well, onto the good stuff, the pictures!

Making the slots for the trigger guard

Beginning of the lower magwell operation.

Making the flat in the rear of the reciever for the grip to sit flush on.

After the first operation.

Don't forget the stepped selector detent hole! (Note the mismatch on the grip flats. For whatever reason they were off by about 10-thou and didn't match up. Oh well, can't win them all.)

Some deep slotting going on.

They match up! At least well enough for now.

Turns out there was an mismatch of about 0.010" where the top and bottom magwell operations met. Turns out that this was actually a good thing though, because the magwell was undersized anyways. Yeah... I uhh... did that on purpose! This allowed me to offset and adjust so that the two magwell operations matched up nicer and opened up the inside dimension a little more.

Offsetting and opening up the inside dimension some more - notice all the aluminum "hair" to the right. Thats one of the coolest parts about doing a finishing pass on a long DOC.

That's better. I could barely feel that little edge with my finger. The pockets are matched to within a few thou now.

Its alive!!! Well at least a magazine fits partially in the magwell.

Flipping over and opening up the inside dimension a little bit more from the top plane.

Now look at that match!

Some close-ups:

However much I hate not letting the machine do all the work, I had to do some hand filing to get rid of the scallops in the corners. I just barely had to hit each corner with a long file to allow a magazine to slide easily in and out. I will have to do some more filing though as some of my magazines are too tight of a fit.

And proof that it fits!

Now all thats left is to chamfer the bottom of the magwell, flip on end and machine a slot in the front of the reciever for the upper to mount to it, and mill the flat and thread the hole for the grip to mount on. Oh, and drill that little hole for the bolt catch pin. Won't be too much longer and I'll be throwin' some brass! Stay tuned!