This is in reference to my 6xc Tubb .160 freebore .270 loaded neck od in a .278 neck chamber
I read a 10 yr old post somewhere on here where David Tubb stated that switching from Norma brass to the then new Peterson shot 25fps faster even though the capacity was the same. Noone commented on this.
I have been shooting Peterson brass with copper DTAC's at 2985 fps. I recently converted some Lapua Palma brass and am now at 3012 fps. Same everything other than the case. I did my own water weight tests and the cases were very close in capacity ie .5% difference. SD's for both loads were in the 10 range with ES around 20.
Based on my trimming experiences the brass alloy softness to hardness ratings on these 3 brands is as expected: Norma>Peteterson>Lapua
So what is happening here? My only guess is that some how the tougher brass has more resistance to fireform and thus exerts a tad more initial pressure down the bore on combustion? If not then what is it?
I read a 10 yr old post somewhere on here where David Tubb stated that switching from Norma brass to the then new Peterson shot 25fps faster even though the capacity was the same. Noone commented on this.
I have been shooting Peterson brass with copper DTAC's at 2985 fps. I recently converted some Lapua Palma brass and am now at 3012 fps. Same everything other than the case. I did my own water weight tests and the cases were very close in capacity ie .5% difference. SD's for both loads were in the 10 range with ES around 20.
Based on my trimming experiences the brass alloy softness to hardness ratings on these 3 brands is as expected: Norma>Peteterson>Lapua
So what is happening here? My only guess is that some how the tougher brass has more resistance to fireform and thus exerts a tad more initial pressure down the bore on combustion? If not then what is it?