I had an old SP1 upper with a crack under the ejection port that I picked up along with a bunch of other parts a couple of years ago.  I really hated to toss it out because it reminded me of the gun I was issued in boot camp at Parris Island in 1977 (except that one had a fwd assist).  One day while I was cleaning up the shop I saw it laying next to an old Remington 513T .22LR barrel and the marriage was made.

I bought a CMMG conversion kit from AIM Surplus and put it in another AR to get the dimension to the bolt face of the cartridge insert and reverse engineer the CMMG guide rail and bolt face then hit the Cad software.  I cut off the old chamber on the Remington barrel to get rid of the original locking pin slots and turned the barrel down enough so that I could slide a barrel extension made to fit the receiver onto it.  Then I cut off the other end of the barrel (to loose the tapped holes from old front site) and re-crowned it.  I silver brazed the extension onto the barrel and set back up in the lathe to re cut the chamber.


I set it up on the mill to cut the guide rail slots, the extractor slot and a slot to take the new feed ramp. Then I drilled a hole for the barrel locator pin.  


I didn’t want to mess up the CMMG kit by cutting the fingers off of the end where it grabs the fake cartridge insert and holds it in place so I made a new bolt guide without the fingers so it could slide along each side of the barrel in the grooves.

I hadn’t given a lot of thought to a forearm but remembered that I needed to make a barrel nut to hold the barrel onto the receiver. I’ve made custom barrel nuts for AR’s before and since I didn’t have to deal with the gas tube this one would be easy.  I remembered that I had some .095 walled 1.5” pipe left over from another project and brazed it to the barrel nut after drilling some holes to reduce weight.

I will probably mount a retro scope onto the handle because shooting open sites with bifocals is too challenging.  I might design a new front site base later on if I get to feeling guilty.  I still need to make a spacer to fill the large front take down pin hole and give it a good Duracoat paint job. Oh yeah, I need a charging handle too. I should be able to test fire it pretty soon.  

Very cool!!

+1

Looks pretty intereseting so far. I want to see how the comes out.

i have a few charging handles for sale if you need one