.204 OAL and CBTO match chamber

[Sigfla]

Just measured several bullets OAL and CBTO (base to Ogive) in my Pac-Nor .204 chamber. The chamber is cut for a .230 neck but I do not know the freebore measurement. Can anyone help me out with some observations based on these measurements?

32 V max
2.2675 OAL
1.9105 CBTO

39 Sierra Blitz
2.2955 OAL
1.9405 CBTO

30 Berger (discontinued)
2.2760 OAL
1.9650 CBTO

 

[Tommie]

I believe this has become the de facto standard.

 

[L.Sherm]

If you have a .230 neck then its not a saami chamber. The saami is .232 and .100 freebore.

 

[Sigfla]

I believe this has become the de facto standard.
View attachment 1728121

Yep I have seen Ricks PTG chamber many times. I think I may have the same cut but I am just not sure on the freebore. Based on my posted measurements I am pretty sure I have a short freebore. I just dunno if it’s .015 or slightly longer. The gun was bought used with maybe 40 rounds through it. The data I got was for 30 grain Bergers with blc2 at 2.240 oal. Given my measurement that would be around a .02-.03 jump off the lands.

 

[Sigfla]

The reason I am wondering is bc I think I may have a .062 throat. I base that on some calculations from other folks OAL and CBTO using 39 grain Bergers with a known .100 freebore. I know I can’t 100% replicate their comparator or micrometer measurements or even their modified case but all things being equal I worked some numbers and hit around .062 and I seem to remember having seen a ptg chamber drawing and discussion with a .230 neck and .062 throat.

 

[Woollybugger]

If you can seat above the shoulder-neck (donut) and stay under mag length shoot it. If you want it longer throat it. You can rent a PTG uni-throater from 4D

 

[Sigfla]

If you can seat above the shoulder-neck (donut) and stay under mag length shoot it. If you want it longer throat it. You can rent a PTG uni-throater from 4D

Not wanting to mess with it. It shoots .1 with the 30 grain Bergers. I was really just trying to pin down if I had a zero freebore or a .062. After more research I found the threads that reference PacNor using a .062 freebore on their match cut chamber. Others have spec .015 but if not asked for it seems they use a .062 for non SAAMI spec chambers.

 

[Rick in Oregon]

The Pac-Nor print Tommie shows above in Post #2 is mine that I modified slightly from Todd's original 204 Match chamber. Mine has .015" freebore vs the .062" FB that PN will use if not requested otherwise. Just be aware if you use this or a similar reamer design, shooting factory ammo in this chamber is not recommended.

I had Dave Kiff at PGT grind my 204 Match reamer for my M700 11T build. The rifle shoots lights out.

 

[RegionRat]

Rick, what bullet/seating were you intending to run when you had that reamer dimension changed?

 

[Sigfla]

The Pac-Nor print Tommie shows above in Post #2 is mine that I modified slightly from Todd's original 204 Match chamber. Mine has .015" freebore vs the .062" FB that PN will use if not requested otherwise. Just be aware if you use this or a similar reamer design, shooting factory ammo in this chamber is not recommended.

I had Dave Kiff at PGT grind my 204 Match reamer for my M700 11T build. The rifle shoots lights out.

Beautiful gun. I am leaning towards doing a barrel swap on my Savage .204 with your specs or maybe a 10 twist. We shall see how far I go once I finally get off my butt and load some rounds for my GreTan Remington .204. In any case I want to start loading for my Dakota .243 in the future as well. Kids are older (graduating high school) and not taking as much time out of the schedule as the last few years. I finally have space in the new house to setup my bench and do what I want now as well.

 

[Rick in Oregon]

Rick, what bullet/seating were you intending to run when you had that reamer dimension changed?

RR, in that rifle, the bullets of choice are the Nosler 32gr BT and Vgdn, and the 39gr SBK, mostly the 39gr as the rifle is my LR rat rifle for work past what my 221FB and 20VT are usually used for; work past 400 yds.

With that chamber, I'm able to reach the lands with all bullets mentioned. I get .2" groups with .080" off the lands, all the way down to .005" off the lands. The 204 is indeed very accurate even with ridiculous jump distances of .100"; SAAMI factory dimension.

 

[Coyotefurharvester]

20-30 thousandth jump is very reasonable for the 204R, factory designed to be very jump tolerate.

 

[RegionRat]

RR, in that rifle, the bullets of choice are the Nosler 32gr BT and Vgdn, and the 39gr SBK, mostly the 39gr as the rifle is my LR rat rifle for work past what my 221FB and 20VT are usually used for; work past 400 yds.

With that chamber, I'm able to reach the lands with all bullets mentioned. I get .2" groups with .080" off the lands, all the way down to .005" off the lands. The 204 is indeed very accurate even with ridiculous jump distances of .100"; SAAMI factory dimension.

Thanks Rick.
I have ever only used Greg Tannel's reamer for bolt, and John Holliger's for AR bbls. They both spoiled me.