I’ve only been reloading rifle cartridges for a couple of months but I’m starting to see some interesting relationships between case overall length and brass type. I’ve been testing several different powder and primer brands. Primer brands F210M and CCIBR2 have been loaded with Powders IMR4064, Varget and Reloader 15. Brass types are Lake City Match and M118LR, Winchester and FC brass.
My rifle is a REM 700 VSS .308 24” barrel with 1:12 twist.
My most accurate loads have been with Lake City Match brass and Lake City LR M118 brass.
These Loads are Varget 45gr F210M primer Lake City Match brass and 168gr Nosler CTBT seated 2.827“. The Velocity measured, 2690fps with a .244” five shot Group.
The Next most accurate was 42.5gr IMR4064, CCIBR2 primers, Lake City M118LR Brass and 175gr Sierra MK seated to 2.827”. Group size was .335” and Velocity 2630fps.
I just started testing the Reloader 15 this weekend. No firm data yet.
What I’ve noticed is that the commercial cases, Winchester in particular requires a deeper seating depth to get the better groups. Basically the depth is somewhere around SAMI standard. Still testing.
I noticed a huge difference in group size when I tried the 2.827” seat depth with the Winchester brass. My groups ballooned to 1.4 inches until I started seating the bullets deeper.
I’ve read that there is a relationship between seating depth the jump to Lands and groves. But my data says there is a stronger relationship between case design and seating depth. I would assume that the relationship is case volume or density and seating depth.
Does anyone have any more data on this.
One other question; I’ve been testing during outside temperatures of 45 to 55 degrees Fahrenheit and have been unable to achieve the max velocities(above 2700fps) from loads posted on any reloading table . Why is that?