Barrel Tester, Looking For Ideas

Sorry guys, I wrote a wrong dimension down. You should take .125 from the action face, leaving the space between the action face and flat bolt face at about .500.

All dimensions are approximate. As Mike said, you would have to get the shoulders exact so that when you screw a AR barrel minus it's barrel extension on and seat it, the headspace would be correct.
 
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jackie schmidt said:
Sorry guys, I wrote a wrong dimension down. You should take .125 from the action face, leaving the space between the action face and flat bolt face at about .500.

All dimensions are approximate. As Mike said, you would have to get the shoulders exact so that when you screw a AR barrel minus it's barrel extension on and seat it, the headspace would be correct.
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Will do. I will have a nice project.
 
Mike Bryant said:
That would be pretty simple to make. I'd bore and thread a piece for the inside thread. Then cut a thread on a barrel stub in the lathe to fit the inside thread, Turn the insert around and screw the insert onto the threaded barrel stub and then cut the external thread to fit the receiver with whatever shoulders you need to make it work. Doing everything like that, all your threads and shoulders would be concentric and at right angles. The hardest thing about making the insert would be to get the headspace correct and that would take some measurement to get it correct.
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Mike,

Thank you. I believe I understand what you articulated. I may save a little time, I have few shot out barrels, I can unscrew the barrel extension on one and cut off a stub from tenon side long enough to chuck up.
 
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Asa Yam said:
Good advice - IIRC, the US Army has taken this route due to bolt fractures after 3,000 to 10,000 rounds. Why? Cyclic motion + corrosion pits = fatigue tester. See https://www.sciencedirect.com/science/article/pii/S1350630705000221 for a report on this. Note the failure pattern of the bolt is typical for ARs - failure is normally at the lugs on either side of the extractor due to the "missing" lug. There have been instances where the bolt failed at the cam pin hole as well - again, corrosion and cyclic loading are generally the cause, with heat treatment being a factor as well.

AR-15 bolts are relatively cheap, and available. (About $50 to $75 for a "normal" bolt assembly.) Surgery (i.e., fixing eyes, hands, and face) is not.


Clean with 16? Think you're slipping. ;)

P.S. Think the AMU's rig is the direction you want to go.
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Asa,

Nice to hear from you, bud. Thank you for the advice and link.

If I recover well enough from my total knee replacement on 3 April, I may go with Diaz, and Bobby Adams to the match In Hawaii in Sep.

Nez
 
NezRongero said:
Mike,

Thank you. I believe I understand what you articulated. I may save a little time, I have few shot out barrels, I can unscrew the barrel extension on one and cut off a stub from tenon side long enough to chuck up.
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I wasn’t thinking about saving time. I was thinking of alignment. If you cut the barrel stub threads in the lathe and leave it in the chuck, then the threads are as in line with your lathe bed as they can be and so will the insert when you cut the threads on it. If you chuck up an old barrel, you can’t be sure that the threads are straight even if you get the old chamber centered.
 
Mike Bryant said:
I wasn’t thinking about saving time. I was thinking of alignment. If you cut the barrel stub threads in the lathe and leave it in the chuck, then the threads are as in line with your lathe bed as they can be and so will the insert when you cut the threads on it. If you chuck up an old barrel, you can’t be sure that the threads are straight even if you get the old chamber centered.
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Basic machine shop practice.
 
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