REAMER FREE BORE MEASUREMENT WITH NO PRINT

[ricco1949]

Is there a practical way to measure freebore on a reamer?

My friend acquired a 2001 PTG, .271 Nk, 6BR reamer with no print.

I've tried inserting the reamer in a fresh barrel to touch point and measuring the distance to the neck. I'd have to face the barrel to get as accurate as possible but this still seems rough at best.

Any tips?

 

[Alex Wheeler]

Measuring a reamer freebore

I posted this the other day but that thread is gone. I thought I would put it up because it may help someone save some grief. This is a quick easy way to verify that your freebore is close to what it should be. I can usually get within .005" of the true length doing this. Which is close...

forum.accurateshooter.com

 

[ricco1949]

Thank you Alex.

I did try to look for the grind change but it is so faint to the naked eye that I wasn't sure I was seeing it correctly.

I tried my visor and 4x cheaters and it's still faint but visible in the right light.

After measurement it appears to be .060+/- .

BTW, it pretty much agrees to inserting the reamer with bushing into muzzle of an old barrel with a fairly fresh flat crown. That's how I confirmed I was correctly seeing the grind change.

 

[Jud96]

Alex’s advice is solid.

Recently I found a 6PPC reamer at the shop that was simply marked “6PPC 0.269NK”. I couldn’t find the print so I took all the dimensions I could with the 0-1” mic. The freebore on PPCs is typically 0-.070, so there’s not much of a straight. My solution was to dial in an old piece of barrel and short chambered it so the throat, neck, and shoulder were complete. Then I made up a dummy round with the bullet I use and a sized piece of brass. Put the piece of brass in the chamber and measured from the base to the back of the barrel. Then seated the bullet progressively deeper until I couldn’t feel it “grab” the rifling. I measured from the base of the case to the barrel while seating the bullet deeper so I knew I was getting close. This showed that the freebore was at least sufficient for the bullet I’m using and wasn’t too long or short.