6BR Norma Berger 105 COAL?

[pelikan800]

Question on Berger 105 gr. BTHP COAL. I have a Rem. 700 action I did a Remage on with a 26" 6mmBR Norma 1:8 twist Criterion barrel (through NSS). I've shot 75 handloads to break in the barrel so far using Sierra 95 MK's with no issues (loaded to 2.35" COAL). Yesterday I began to reload some Berger 105BT bullets (Berger part #24428) over Varget using the data in the Berger manual. They gave a COAL of 2.441". That turned out to be way too long to chamber in my rifle. I did rebarrel my rifle using Go/No Go gauges so it should have correct headspace. Using my Hornady OAL tool and the Berger bullet, I determined that the max COAL with the bullet touching the lands is 2.325".

If Berger is using this COAL in their manual, shouldn't it chamber in most rifles? I've reloaded .223 and 6.5CM for my R700 factory rifles (in addition to thousands of pistol reloads) in the past and never had an issue with chambering. Your thoughts?

 

[Bill Norris]

If Berger is using this COAL in their manual, shouldn't it chamber in most rifles? The answer is no. Because Berger set that particular COAL for that particular barrel and chambering. Aftermarket barrels can be chambered with different lengths of throat for different lengths of bullets. Go/No Go gauges only determine headspace.

 

[PatMiles]

Gonna have to do your homework on your rifle.
https://www.wheeleraccuracy.com/videos
Watch "Finding your lands".

 

[rwj]

Gonna have to do your homework on your rifle.
https://www.wheeleraccuracy.com/videos
Watch "Finding your lands".

If the chamber is throated for a lighter bullet, you may find that a 105 grainer will be seated deep into the case thereby reducing volume for powder. Cases may display signs of high pressure at lower charge weights than cited in the manual.

 

[pelikan800]

Yes rwj, that is a concern. Because I can't seat the bullet out as far as the manual suggests, I worry using any of the load data with a deeper seated bullet could cause pressures that are too high. I might start at the low end of powder volumes and see what the velocities are (I have a magnetospeed). Less powder with the deeper seated bullets might give me the speed and groups I'd like to see.

 

[Comandante]

Pelikan800: You have a PM.

 

[expiper]

my dasher with 150 FB gives ~2456 LOAL ---your is ~125 shorter so your FB must be ~020-030"--Roger

 

[pelikan800]

Roger, your calculation sounds about right. I'll probably begin 20 thou off the lands and work up some initial loads. Thanks!

 

[pelikan800]

My question at this point is powder amounts. Berger suggests 26.5 - 29.4 gr. using Varget and a 2.441" COAL. Now that I'm probably going to be around 2.32" COAL and therefore a smaller internal volume, do I start at 26.5 gr. of Varget and work up until stiff bolt lift etc. or start even lower? Thoughts...