Brass weight

[Allen in MT]

Just got a 100 count box of Alpha 6mm CM SPR. Looks good so I loaded 5 with the same load I had in my Hornady LRP brass which was 39.8 grains of H4350 Took them to the range to fire them and ended up with a tight extraction. bolt lifted up ok but couldn't pull bolt back, had to beat it back with palm of my hand so I shot a second, same thing. Got to looking at primer an it looks like they are cratered.
Got back to the bench and de primed and weighed the empty case's and then weighed the Hornady cases. The Alpha brass weighed right at 10 grains heavier than the Hornady cases. Weighing 3 case's of each the Hornady weighed Ave 148.7gn and the Alpha was 158.9gn avg, so that is telling me less case capacity, got to start with a lower powder charge.
If you have 6mm cm Lapua cases can you get a avg weight of 3 cases without primers and the same if you have Peterson 6mm cm cases.

 

[Rule3]

Case VOLUME (H2O) is a better indicator than case weight.

 

[troy fairweather]

this is why you need to drop the load some when you change things.

 

[mdi]

Water may be a better method of measuring, but weighing cases is a good indicator if one mfg. is different than another...

I must have made a mistake 30 years or so ago because I always reduce a load if I change any component...

 

[Allen in MT]

Thought it would be a start load as Hodgen start load is 39.0 gns & I used 39.8. Guess will have to drop 1 1/2 or 2gns. will do H20 weight to see differences. Was just kind of curious as to what case weight was with different Mfg. I've been reloading since 1971.thanks

 

[Walkalong]

Looks good so I loaded 5 with the same load I had in my Hornady LRP brass which was 39.8 grains

Change a component? Start over, work it back up.

That said, if you had weighed the brass first you would have known to back off some to start for sure.