Freebore and lead question

[Swift4Yotes]

I sent a few 6 Hagar dummy cartridges with 70 ballistic tips seated at 2.280" to PTG as they said they could custom grind a finishing reamer to produce .020" bullet jump at this cartridge oal. The reamer they stock is a .117 freebore and they said they would custom grind it to 0 freebore .
Fast forward several month and our barrels are now chamber with this supposedly modified reamer and there is exactly .100" jump with cartridges loaded exactly like the dummy rounds we sent in.
Now for the question.....
The cutting portion of the reamer just forward of the shelf or case mouth edge measure .241ish diameter across the flutes and tapers to .231" ish (hard to measure) within the .300" or so length up to the pilot. I am curious if this .010 taper is standard and just the normal lead angle or was this what was ground in to shorten freebore. I'm concerned we got an unmodified reamer. Thanks!

 

[STS]

Welcome to PTG.

 

[Dusty Stevens]

Cut your losses and send the sammy hagar cases to manson and get exactly what you want

 

[Fuj]

JGS has been doing mine lately.....

 

[Edd]

I sent a few 6 Hagar dummy cartridges with 70 ballistic tips seated at 2.280" to PTG as they said they could custom grind a finishing reamer to produce .020" bullet jump at this cartridge oal. The reamer they stock is a .117 freebore and they said they would custom grind it to 0 freebore .
Fast forward several month and our barrels are now chamber with this supposedly modified reamer and there is exactly .100" jump with cartridges loaded exactly like the dummy rounds we sent in.
Now for the question.....
The cutting portion of the reamer just forward of the shelf or case mouth edge measure .241ish diameter across the flutes and tapers to .231" ish (hard to measure) within the .300" or so length up to the pilot. I am curious if this .010 taper is standard and just the normal lead angle or was this what was ground in to shorten freebore. I'm concerned we got an unmodified reamer. Thanks!

A taper of about .010" is normal. The front end of the reamer is usually about .005" smaller than the bore diameter. The length of the taper depends on the throat angle.

 

[gunsandgunsmithing]

The most common lead angle is 1.5°, sometimes expressed at 1°-30 minutes.

 

[DaveTooley]

Also understand that you need to add about .015" to any stated FB length which is the 45 degree angle at the end of the neck.
Under some magnification you should be able to tell if the reamer has a cylinder section in the throat. There will be a difference in the grind marks as it transitions from a cylinder to the taper. Good luck

 

[Dusty Stevens]

And usually a regrind has a longer nose before the bushing than normal. Looks like a real long freebore but its under the size that would cut