6mm Creedmoor help

[Laceygm]

Need some help with a load.

I worked up a load for my 6mm CM that was shooting pretty good last week. Took the load out today and was all over the place, showing pressure signs and SD was in the 30s. Temperature was similar but was 1000’ higher in elevation.

Load is 105 gr Hornady HPBT Match, 41.8 gr H4350, CCI 41 primers and Lapua small primer. 2.727” OAL.

I can’t find much info using Lapua brass.
According to Quickload I’m on the high end of the pressure curve, but under SAAMI max.

Anyone using these components that is willing to share info would be appreciated.

 

[ShtrRdy]

Was the brass new the first time out and 1x fired the second time out?

 

[918v]

How did you resize the brass? Or was the load assembled using new brass?

 

[TSULLI]

Try to identify any variables that could possibly have been introduced no matter how small they may seem and verify all components used. Just as it's asked above, any difference in brass was the first thing that popped in my head as well.

 

[Laceygm]

Was the brass new the first time out and 1x fired the second time out?

All virgin brass

 

[Laceygm]

How did you resize the brass? Or was the load assembled using new brass?

Virgin brass, FL resized out of the box before I loaded it.

 

[TSULLI]

I can’t find much info using Lapua brass.
According to Quickload I’m on the high end of the pressure curve, but under SAAMI max.

Lapua brass can be pretty thick compared to some other brands. That lowers internal volume which raises pressure but it's odd that you didn't have the problem during your last outing though. An elevation change like you mentioned wouldn't have an effect like that. H4350 is part of Hodgdons extreme series so it is very temperature stable which rules that out... I am interested to see what others might have to say about it.

 

[Laceygm]

Try to identify any variables that could possibly have been introduced no matter how small they may seem and verify all components used. Just as it's asked above, any difference in brass was the first thing that popped in my head as well.

The load was identical. All new brass, all components from the same lot.
The only differences I can see is today was about 5 degF cooler, 1 inhg lower and about 800’ higher elevation.
When I shot last week, I was in load development. Only shot 5 rnd of this exact charge but went .3gn higher with no pressure signs, but this was the best load. I had a .45” group at 100. Today wasn’t able to hold better than 1.5” and high pressure.

I know the data is at the top edge of charge according to Hornady and Sierra. According to Hodgdon I still have a little way to go. I am thinking I just need to step back a little since I am using heavier brass.

 

[jpjulian]

Try dropping the load back 1 full grain to 40.7-40.8 and seat to a base to ogive of 2.140 and see what the target tells you. You might be pleasantly surprised......

 

[Laceygm]

Try dropping the load back 1 full grain to 40.7-40.8 and seat to a base to ogive of 2.140 and see what the target tells you. You might be pleasantly surprised......

I’ll load some up to try out next weekend. That’s the same charge I’m using for 6.5 CM with pretty good results.
Thanks