Where is the limit for 6BR?

[Rat Rifle]

There is no one right answer, but I can Guarantee you that the hottest load is not the Best load, in a Straight BR.

Every single case head separation that I have seen has been caused by repeatedly bumping the shoulder back too far. Your report makes me want to know how you set your FL dies.

Perhaps to not “derail” the OP’s original question, how I set My dies could be addressed in a separate thread ?

 

[Bob3700]

Perhaps to not “derail” the OP’s original question, how I set My dies could be addressed in a separate thread ?

I have 6 mm BRX and 308 brass that has more firings than I can count. Only bump shoulders back .0015” each sizing n anneal after three firings. Have never had a case head separation. Primer pockets will open up and be the reason to discard a case.

Agree with Boyd on this one. Case head separations are typically associated with too much shoulder bump.

 

[nakneker]

You want to find the limit? Start low and work your way up. Never take someone else’s load at face value and assume your rifle will shoot it just fine. Thats a bad habit and it happens a lot, sometimes with consequence. There’s nothing wrong with duplicating someone else’s load, just work up to it.

 

[YBPS]

I have had 2 6BR’s with 1:8 twist. 29.5 of Varget has been the load with both barrels, seated touching the lands with 105 Hybrids. One barrel was faster 2840 and the current barrel is slower 2770. Both 26”.

 

[mgunderson]

Whatever the limits is.... we are way beyond it! Just my opinion.

 

[J.D.Erwin]

Whatever the limits is.... we are way beyond it! Just my opinion.

Every 6br has a limit but every one is difference to the barrel and action being use
for that setup your load development and time at the range will tell you what you need to know.

 

[NC/Br Shooter]

I know 34g of Varget is too much for 80 grainers.
Even 32.5 Varget with 80s is still pretty hot.
That's bra though.

 

[Laurie]

You say data from 'books' - presumably reloading manuals?

Note a degree of confusion here. There are two 6BR chambers with different sets of load data - 6mm BR Remington and Norma. Many US sources, especially older ones, are for the short-freebore original Remington version, and as powder / bullet manufacturers have to chamber their test barrels to SAAMI specs, any such data are for shorter COALs and produce SAAMI maximum pressure with lower charges.

That's changing now with for example Sierra #VI data for the Norma chamber version, and looking at Hodgdon's latest incarnation of its online menu driven facility, it now has both versions - which I'm sure must be recent. (Trying to do a like for like comparison on this facility, I see why Hodgdon has added the Norma option. It only gives loads for Accurate brand powders which Hodgdon recently acquired and has obviously used the former Accurate company loads data. There is none for IMR, Winchester, and Hodgdon powders and the H4895 loads are therefore only for the Remington chamber.)

The 107gn Sierra MK is therefore tested by Sierra in its #VI edition data with the bullet seated very deeply indeed at 2.25-inch COAL. Most people having a 6BR rifle built today for anything other than for light bullets for short-distance BR use something much closer to the longer Norma chamber freebore, in many cases longer still with the rifle throated to suit the chosen bullet(s). The CIP (European standards agency responsible for this version of the cartridge), COAL is 2.440" and many of the higher loads you've seen quoted will be for yet longer freebores and COALs giving yet lower pressures.

(I say Sierra #VI is now the 'Norma' version, but the COAL for the 107gn SMK is still a short 2.350", and I suspect the max H4895 charge will be as per 'Remington' data in older editions. The recently introduced 110gn SMK is seated to the CIP Norma version OAL at 2.450-inch and the H4895 max is 0.1gn higher despite the heavier bullet.)

 

[Kracken McGraw]

You say data from 'books' - presumably reloading manuals?

Note a degree of confusion here. There are two 6BR chambers with different sets of load data - 6mm BR Remington and Norma. Many US sources, especially older ones, are for the short-freebore original Remington version, and as powder / bullet manufacturers have to chamber their test barrels to SAAMI specs, any such data are for shorter COALs and produce SAAMI maximum pressure with lower charges.

That's changing now with for example Sierra #VI data for the Norma chamber version, and looking at Hodgdon's latest incarnation of its online menu driven facility, it now has both versions - which I'm sure must be recent. (Trying to do a like for like comparison on this facility, I see why Hodgdon has added the Norma option. It only gives loads for Accurate brand powders which Hodgdon recently acquired and has obviously used the former Accurate company loads data. There is none for IMR, Winchester, and Hodgdon powders and the H4895 loads are therefore only for the Remington chamber.)

The 107gn Sierra MK is therefore tested by Sierra in its #VI edition data with the bullet seated very deeply indeed at 2.25-inch COAL. Most people having a 6BR rifle built today for anything other than for light bullets for short-distance BR use something much closer to the longer Norma chamber freebore, in many cases longer still with the rifle throated to suit the chosen bullet(s). The CIP (European standards agency responsible for this version of the cartridge), COAL is 2.440" and many of the higher loads you've seen quoted will be for yet longer freebores and COALs giving yet lower pressures.

(I say Sierra #VI is now the 'Norma' version, but the COAL for the 107gn SMK is still a short 2.350", and I suspect the max H4895 charge will be as per 'Remington' data in older editions. The recently introduced 110gn SMK is seated to the CIP Norma version OAL at 2.450-inch and the H4895 max is 0.1gn higher despite the heavier bullet.)

Thanks for this info Laurie, I was curious as why Sierra’s sixth edition was so low on the max charges.