Originally Posted by NesikaChad
I have the reamer print book published by David Kiff/PTG.
30-06 AI length from case head to datum line on the shoulder: 2.0773"
25-06 AI length from case head to datum line on the shoulder: 2.1127"
For reference, the datum line of the shoulder is where it measures 3/8" of an inch in diameter.
Based on the print, if your gunsmith were to use the 25-06 gauges the cartridge would not technically be an AI 30-06 as it'll end up longer.
In practice it's going to resemble something like a Gibbs/Ackley inbread deliverance thing that goes bang. You can't just pull material out of thin air and in this situation it's likely the case will steal material from the neck area in order to fill the dimension.
NOW, that being said, you could probably still use the gauges. You have a couple options:
1. If your guy is "Johnny on the spot" he can chamber the gun and headspace the gun to have the GO gauge stick out the ass of the chamber by the difference.
OR (and if your really a wildman)
Just chamber the thing to the 25-06 depth and run it. All your going to do is have a neck a smidge shorter than the next guy's. If you have good dies it will very likely not hurt a thing.
IF you do this just be sure to do the following to avoid going to the hospital:
On your initial fire form use a heavy bullet, a moderate charge and SEAT THE BULLET LONG< LONG< LONG !!!!
LONG I SAY!!
Here's why. With a gun being nothing more than a pressure vessel and brass being nothing more than a balloon you have pressure exerting at a right angle to whatever it contacts. That being said you want to ensure YOU are controlling where the brass stretches. By seating your bullets long you ensure your case is firmly planted against the bolt face. This offers only one choice to the case; it has to pull material from the neck and grow only towards the muzzle end of the chamber. This is harmless as the backside of the case maintains integrity. All widgit wildcats fire form like this.
It's when you have a case rattling around in a chamber like the proverbial sausage fest/hot dog hallway analogy that you run into problems/broken parts (to include body parts)
If the pressure exerts at a right angle the bulk of the case surface area is against the inner walls of the chamber. The brass will literally "bite" and hold fast (especially in an AI since there's almost no case taper) If the brass has nothing in front of it to ensure your case head is supported then guess what? When the primer gets whacked everything tries to move forward until either the bullet or case shoulder stops it. Then the fire gets lit and the case head stretches right back to the bolt face. Again that material has to come from someplace. In this case its from the case body, making for thin webs that love to split due to work hardening and/or pressure. If this only happened one time, its likely you'd be fine. Where it becomes a big issue is when you go and size your brass to run like a raped ape (short shoulders etc) Now your stretching it over and over and over, pulling from web/body everytime and then squishing it back into shape.
Brass will only tolerate this for so long. Your gun will "sneeze" and you'll be picking crap n brass from your face.
Point is you now have a case that wants to kill you when you least want it to. . .
In your situation all a guy has to do is ensure the bullet is long and then fire form. Once you do this adjust your dies to size the case just enough to facilitate good feeding/extraction.
Best advise, get the right gauges. PTG (David Kiff) sells em for under $30 bucks. Can't go wrong with proper instrumentation/gauging.
Hope this helped.
That's good to know Chad !
I didnt think it was the same but didn't know for sure, and I never assume anything when it
comes to chambers and headspace.
It worries me that a gunsmith would assume something like that, Oh Well, it's a good thing
you questioned the use of the different headspace gauge.
As the owner of a custom rifle
everyone should be fulley aware of the chamber dimensions
and the head space that the smith intends to give you and why.
Some times a smith will use a reamer that will work but may not be exactly what you want
just because he has one. and doesen't want to charge you for one. (Not a good reason)
Get what you want even if you have to buy the reamer your self.
I have rechambered many rifles with a chamber that would not work unless the shooter/owner
loaded special brass, seating debths and even bullets with odd diamenters.(One had a barrel
with a bore dia. of .3085).
It is allways good to ask questions to be sure.
J E CUSTOM