This is a discussion on One of the Last Entreprise receivers within the Gunsmithing forums, part of the M14 M1A Forum category; I saw your M14 build last year and I followed your build on the '92 Winchester. This is going to be fantastic! Lloyd...
I'd suggest leaving it as is. It's a great example to have in a collection. It's too bad that Entreprise didn't do a better job on there receivers. I built several and rejected several for builds as they were out of spec in too many areas.
I keep a Lithgow M1 unfinished receiver in my collection as well as LRB M14 and AR receivers in various stages of finish machining. They are all interesting.
You know if there is a receiver hiding in that chunk of steel I have to bring it out. I did some checking looks like it is machineable although they made some of there roughing cuts very close to not cleaning up especially front of receiver bridge and rear bolt passage .
I'll confirm everything before starting but first step will be facing receiver and boring barrel thread bore and rear bolt passage in line . Followed by timed single point threading the barrel thread.
This will become the datum centerline that all future machining referances from. Over 240 different machining operations will be envolved in this .
And all will be machined using a 12 x 36 Grizzly lathe also used will be a 112 year old Hardinge Brothers bench miller I converted to use on my lathe. Same set up I used on the Lithgow M1 casting and M14 casting ,both fully documented with pictures of each set up on the WeaponsGuild.
This is why I love the M14, lots of soul goes into making that reciever. It's also pretty neat your using the old machine and not the newer computer guided ones. The guys I work with joke about the old hydraulic bores and mills we used to run required a brain to operate, the new electric ones are push a button and sweep the floor.
Did some more measuring today and found the .730'' bolt passage moved off location when they rough drilled it. It going to be real close if it cleans up.
Same with front of bridge they rough milled straight cut but it finishes on 5 degree angle . Nothing is on size ,but they rough drilled elevation/windage holes , connector hole,and scope mount hole.All are .025'' or so under spec .But I only have .010'' on scope side flat and legs .So I'm going to have to do so set up and move receiver around so everything works out to print.
Backs of legs are real close to size so I cant move a lot .
My hats off to you. I don't know how you're able to accurately determine that you've got material everywhere. I've tired it in the past when trying to machine rough forgings and have had a tough time. have had to shift the whole forging (not a partially machined billet) so that it barely cleans up on one side while taking 1/2" off the other, but nothing as complex as an M14 receiver. I'm also amazed at the work you're able to turn out with your equipment. I'm not familiar with your lathe/mill setup, but have tried (unsuccessfully) to turn small parts on bench top lathes, and they just weren't rigid enough to do accurate work. Based on your previous work, I think that you could probably do it with a "Smithy".
Looking forward to seeing your posts on this. I'm hoping that you don't find any previous machining errors that prevent you from using this.
I think it would look cool if you only machined the operational areas and left whatever you could in the rough format. Would it be possible to get a barrel that has inner rifling and threading done but square outer and block stock as well. Kinda Fred Flintstone meets M1A.