Free Bore advice please

[thekubiaks]

I need some advice on how to proceed please. Instead of boring you with all of the details, here is my problem. I had two 6.5 x 284 LG Benchrest guns built by two reputable gunsmiths. Both guns were built with .290 necks and designed to shoot the 142 SMK's. The problem is, I forgot to specify the freebore and the guns have different freebore dimensions. One gun with the longer freebore shoots a lot better than the other.

I have both reamers and can :

1) mount the barrel on the lathe and touch up the chamber by running the reamer with the longer freebore to match the other chamber or

2) I believe that Dave Kiff has some kind of tool that will allow me to increase the freebore without disassembling the barrel and action.

Which do you recommend. Thanks for the replies.

 

[JerrySharrett]

If you have both reamers, and the drawings for both, and the only difference is freebore length, remove the barrel with the shortest freebore and run the longer freebore reamer in BY HAND. If you are very careful and go by sensible feel, you will get a better job and with less danger to you or the barrel by running the reamer in by hand.

You will need a good tap handle type wrench and also the proper pilot bushing for the reamer.

This style wrench will give the best control. Unfortunately this auction is ending in a few minutes. I'm just using this picture for illustration.

http://cgi.ebay.com/Starret-No-91-B...5|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

 

[thekubiaks]

Thanks Jerry, that sounds like the easiest way to do it. Amazingly, the freebores differ by .060" I have the correct reamer pilot and should be able to touch it up. Regards.

 

[Don]

Thanks Jerry, that sounds like the easiest way to do it. Amazingly, the freebores differ by .060" I have the correct reamer pilot and should be able to touch it up. Regards.

You are going to have to perform more cutting work than just running the reamer in deeper. Both shoulder (unless a Savage nutted rifle) and breech face will also have to be machined.

Might as well do all this work in a lathe................Don

 

[Bob Kingsbury]

If both barrels were fitted correctly and the only difference is the freebore,
there is no reason to machine the action face again. If your lucky
and both reamers are identical, you can very carefully use a reamer
extension and deepen the throat with the longer throated reamer.
This can be done without changing the headspace if you are carefull.
Be sure to use cutting oil and brush the barrel when your done
to remove the trailing edge bur in the throat.

 

[Bnhpr]

175 min f.b. and .188 max f.b.

 

[JerrySharrett]

You are going to have to perform more cutting work than just running the reamer in deeper. Both shoulder (unless a Savage nutted rifle) and breech face will also have to be machined.

Might as well do all this work in a lathe................Don

Don, read again what he describes. Am I missing something or are you? We sure don't want to steer him wrong.

 

[Don]

Don, read again what he describes. Am I missing something or are you? We sure don't want to steer him wrong.

Hi Jerry,

My feeling is that no 2 different manufactured reamers are going to have the exact same base-body to neck-transition dimensions, and because of this, running a different reamer into a previous reamed chamber to cut a new freebore/throat only, will also require running the reamer in a bit further to clean up all body dimensional differences thereby increasing headspace, thereby necessitating shoulder and breech end cuts.

Best scenario would be that existing chamber is smaller and the .060 freebore reamer is slightly larger thereby cleaning up existing smaller chamber while cutting new .060 freebore/throat without increasing headspace, and necessitating other cuts.

Re-thinking this, if a borescope is available, re-cut the freebore/throat using your hand ream method, borescope it..........if all is cleaned up, good to go, if not chuck up in lathe and make remaining cuts.............Don

 

[JerrySharrett]

If you have both reamers, and the drawings for both, and the only difference is freebore length, remove the barrel with the shortest freebore and run the longer freebore reamer in BY HAND.

Hey Don, note what I posted in post #2 above.
You are correct in that if there are other dimensional differences, the entire chamber needs to be rereamed with the desired reamer.