Barrel Set Back

[PMA3]

I have a 1000 yard rifle that was built by Bob Hart SR. in 1974. In 1975 I shot several matches with it at Williamsport but mainly used the rifle for long range groundhogs, then sort of retired it in the late 70's.
The rifle has a #4 Hart action, Hart 2 oz trigger, Hart 1.350" straight taper 30" barrel chambered in 7MM Rem Mag and a Hart heavy walnut stock with a 4" forearm. The barrel now has 847 rounds through it and would like to get some information on barrel set back to help me make a decision going forward...I plan on keeping the same caliber for nostalgic purposes as it would no longer be a competitive 1000 yard gun.

What does barrel set back really mean in layman terms?
After set back, how many quality rounds for this caliber can you usually count on compared to the original # of rounds?
Can you use the same cases? ( I have 200 once fired cases from last year )
Will the head space change and the die need adjusted?

I did do a search on this topic and found some information but not all that I was looking for. Any info would be greatly appreciated in helping me move forward with this project.

Thanks...Paul

 

[stenger]

Things are going to change ! Why not just put a new barrel on it?

 

[Preacher]

Set back is just a term that means cutting a little off the barrel and rechambering it...
You should be able to obtain about as many rounds out of the new chamber as the old one did..
Your old brass will only work 100% perfectly if it was cut with the same reamer....
The headspace will probably change unless you use the same reamer with a stop on it..

 

[mikegaiz]

I have done it twice and never got good results. :'( I think it is better to get a new barrel.

 

[Erik Cortina]

If you use the same reamer you can use the same brass and if a competent gunsmith does it for you headspace will also be the same.

But I do agree with the others, just buy a new barrel. This one lasted you 40 years, I think you got your money's worth! ;D

 

[tenring]

847 rounds is not a lot, even in a 7MMMag. Here is what my smith (well known BR smith) says: If the bore is not severely fire cracked, it can be re-chambered. He recommends not more than 1500 rounds have gone thru my 6BR's for successful re-barrel, and predicts it should shoot well for about half than many (750) again with this extended barrel life.

 

[PMA3]

Thanks to all who responded. I'll take the gun to my gunsmith (Sid Goodling) for inspection of the firecracking and see what he has to say....sounds like a new barrel may be in order.
Erik...I only used the gun about 5 years in the 70's, then shook the dust off it about 2 years ago to work up a new load as all the components I used in the 70's were no longer manufactured. Also, as you suggested back in December, I posted pics of the bullet diameter measuring tool that I finally got completed....it's in the Reloading Forum.

 

[cdparker]

Remember, when you set a barrel back, also take a ¼" or so off the muzzle. Reaccomplishing the crown adds greatly to returning the original accuracy to the barrel.