I finished the project and really appreciate everyone's help and advice. As stated originally the barrel was 1.25" in diameter and 26" long. I used some of the lathe time to experiment with RPMs, depth of cut and feed speed.
What worked the best for me was to expose about 12" of barrel at a time between the chuck and a live center and reduce to the desired diameter using pretty small cuts of .005 to .007 diameter reductions. Yes, this took forever as in hours. I tried both HSS that I ground and indexed carbide and the carbide gave a better finish and liked speeds above 200 RPMs--600 RPMs seemed ideal for the carbide. If I had to do this again, I would experiment more but I'll admit to just wanting to get it done as it was late at night and was slack in my documentation.
Is there a way to get a glossy finish using the lathe? The triangular carbide bit run at 600 RPMs with a slow feed speed did okay. It does not look like a record with obvious grooves but they are there. If a gunsmith gave me a barrel with that finish I'd be very disappointed.
The chambering was as easy as for a bolt rifle until the very end. I had a go gauge and used 3 pieces of Scotch tape (.005") to make a no-go gauge. With more experience I am sure this would have been easier but would rather have had a no-go gauge too. Is there a standard measurement for the distance from the back of the barrel to the face of the locking lugs?
I made no attempt to time the gas port hole and, of course, I drilled through both a land and a groove about 50/50. I also took a big shortcut and used the DRO on the lathe to measure an existing rifle length gas port and just duplicated the position. Would love to have a small mill but that will have to wait.
The lathe did okay and I have no complaints about it. One unexpected issue was when using a range rod to center the bore for cutting and threading the tenon and reaming the chamber, I would get different readings on the .0001" gauge when running the lathe under power VS. taking it out of gear and spinning by hand. I expect that is not normal? I ended up leaving it in gear and turning the pulley on the outside to make sure I was actually centered. Guessing that means the bearings aren't very precise. I was able to get it measure less than a .0001" of runout using this method both under power and by spinning the pulley.
One other surprising lathe discovery. As I was profiling the barrel for the gas block. I was measuring with the DRO, a digital micrometer and a regular Starrett 0 to 1"micrometer. I was doing all of the measuring close to the tail stock. When I got to within .003 of the desired diameter I decided to measure at the location where the gas block would be. Very happy that I did. It was at the desired diameter and one more cut would have been a disaster. Does that mean that there was more deflection of the work item further away from the headstock? The end that would eventually become the muzzle was supported by the live center. The lesson for me is to measure in the location of exactly where you need the cut to be precise.
I put 60 flawless rounds through the rifle yesterday and it feeds from the magazine, ejects normally and locks open on an empty magazine. Maybe that was beginner's luck! I do feel that the mechanical spirits were helping me because I did get lucky a few times!
Thank you all agian for the input.
Henryrifle
