Difference in dimensions between Hornady OAL gauge and my DIY measurem

[soflarick]

1903a3 bolt action.

Hornady OAL length gauge, Hornady modified 30-06 case, Hornady bullet comparator.

Bullet is Nosler CC 168 boat tail

Used the Hornady OAL length kit, got 2.808 with the comparator.

Used my case sized in an RCBS FL die, same bullet, closed bolt, then used dowel to tap a bit to seat the shoulder up against the chamber since I figured the bolt alone wouldn't push the shoulder all the way. I was correct as a couple light taps with the dowel moved the case forward just a bit. Using the comparator, I got 2.833.

The Hornady case headspaced at 2.040, my case (as well as most other cases I checked regardless of manufacturer) spaced at 2.043.

I know some say the Hornady cases aren't going to be perfect matches to the firearm, and to use the "old" DIY system of pushing an empty case and bullet through with the bolt to check true OAL.

Why is there such a difference in OAL between the Hornady case and my case (same bullet)? They headspaced very close to each other, and I pushed my case in all the way with a dowel.

Should I abandon the Hornady kit and just let the bolt determine OAL to adjust bullet setback from the lands when reloading?

I can drill and tap my case to match the threads of the Hornady case if that would help.

Thanks for the help.

Edit: checked my Garand Service Grade. I did not disassemble the bolt for the test, so I'm sure the ejector pushed on my case in the test. Hornady kit measured 2.846, my case and the SAME bullet measured 2.849. I understand there's the difference between the 03a3's bolt action and the Garand's semi auto action.

Edited July 8, 2013 by soflarick

[cotis]

I have been struggling also to obtain reliable measurements for OAL in my 30-06. Please explain in more detail what you are doing with the dowel. Thanks