Would this compromise accuracy?

B

Boyd Allen

Active member
Point one: Threading close to a barrel's shoulder is a skill that takes practice, and can result in mistakes by an inexperienced and/or infrequent lathe operator.
Point two: A thread relief can be an issue when setting a barrel back.
Question: What would be wrong with using a precision ground washer (made from suitable material), installed like a Remington recoil lug, between the barrel shoulder, and the action face? If the tops of the barrel threads were slightly flat, and of a specific diameter, it would seem that a good fit could be achieved over the threads, and there would be not interruption of threads when a barrel is set back less than the full length of the tenon. Yes, I know that it would be inelegant, but would it work with no reduction in accuracy?
 
Depending on the length of the setback and the cartridge, you can live without a thread or two..just mho.
I recently bought a small inset threading tool to get closer to the shoulder.
 
Shoulder, chamber, thread, freebore, throat all dead true or to .0001-.0002, washer .0001 flat and parallel, action .0000-.0001 perpendicular. adds up.
Could you just lose 1 thread in action face? A thread releaf there.
 
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Boyd,

I think Jackie did a thread strength test on a piece he had cut a thread relief groove in, and then threaded over...or something like that. Somebody had taken him to task on this issue, so Jackie, who had the equipment to do so, tested it for strength. The joint finally broke at eleventeen metric ass-tons...far beyond what the joint would experience in a barrel and action joint. Jackie was vindicated, and we all learned something. Hopefully, Jackie will chime in and describe the testing he did.

The point? I think you're trying to fix a non-existent problem. It might be unsightly, but nobody will see it screwed into an action. Pretty is as pretty does.

Justin
 
You mentioned the correct way to do it right out of the gate that being to simpy "Practice" until it becomes second nature so it can be done right and without exception. If one does not have the will he will never find the way. I typicaly only do my own work and the pride I take in doing so is set extremely high and I dang near filled up a five gallon bucket with scrap pieces while going through the learning process on how to do it right. Now I am able do it without really giving it much thought thanks to the muscle memory that has since been developed along the way. What used to be quite frighting has now become the most enjoyable for me as I trully do enjoy cutting threads for what ever the need might be for now.

JLouis
 
Zebra13 said:
Boyd,

I think Jackie did a thread strength test on a piece he had cut a thread relief groove in, and then threaded over...or something like that. Somebody had taken him to task on this issue, so Jackie, who had the equipment to do so, tested it for strength. The joint finally broke at eleventeen metric ass-tons...far beyond what the joint would experience in a barrel and action joint. Jackie was vindicated, and we all learned something. Hopefully, Jackie will chime in and describe the testing he did.

The point? I think you're trying to fix a non-existent problem. It might be unsightly, but nobody will see it screwed into an action. Pretty is as pretty does.

Justin
Click to expand...

That was quite a while back.
The discussion centered around using old take off barrels on different rifles, in this case, a shooter had a 6BR barrel that had came off of a Panda, and wanted to use it on a Rem 700. The barrel was already down to 21 1/2 inches or do.

I chucked the barrel up true, and cut the relief for the Rem bolt nose. I then set the lathe on 16tpi, and set the tool to catch the existing thread in the middle about 1/2 inch up.

I then just established a 16tpi on the tenon to fit the Rem action. It didn't look half bad. I then took and machined a spacer to fit in conjunction with the recoil lug to establish the correct headspace.

The rifle shot just fine.

When wrote this up on the Forum, and all hell broke loose. Dangerous. Heresy.

So, I took time to machine up pieces out of an old unlimited barrel and tested what force it took to make the thread fail.

I was using a 20 ton hollow ram, and neither the "reclaimed" thread or a standard thread failed.
 
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Instead of adding another piece to the assembly couldn't you just use a slightly thicker recoil lug and partially bore it to give the threads the relief needed ?
 
You could if you were going to use a lug. I was asking about situations where you are not. I guess that I should have said that.
 
well then the lug-less recoil lug is still the answer.
start with the thickest, then to thinner as you freshen
the throat.
 
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