Re: .308 Load Data
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rust</div><div class="ubbcode-body">I have sort of the same problem with the .308, more ES/SD than I would like.
Part of the problem is that the primer contributes quite a bit in a .308 say compared to a 30-06, smaller case, less powder and don't forget that modern standard large rifle primers were primarily developed for the -06.
In the high power rifle world, some of the better known (meaning successful) shooters have been using the Russian primers which are the least hot primer that will reliably ignite the powder in a .308, and they are seeing lower ES/SD numbers. They are not using wimpy loads either to boot to 1,000 yards.
Other things which affect ES/SD are neck tension, uniform brass, uniform seating depth, uniform firing pin strike energy, uniform powder charge and even temperature of the rounds.
Just for grins, you might try some of the old .308 standby powder, IMR 4064, carefully weighing out charges to see how your numbers compare. Except for it's temperature sensitivity, 4064 would be my powder of choice. It gets a little peaky pressure wise with heavy loads and higher temps. </div></div>
Yes, a lot of things come into play. My ES isn't awful, but I want much better (approx. 30fps). I keep looking around, but it looks like trying 250/215M with Varget works well as long as you reduce the load.
http://www.6mmbr.com/gunweek097.html
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"><span style="font-weight: bold">Varget Yields Low ES/SD and Lapua Brass Shows Minimal Runout</span>
I headed out to the range, armed with my chronograph, to see if I could find a good load with Varget and the 175 SMKs. I chronographed loads from 42.0-44.0 grains of Varget, using both BR2 and CCI 250 primers. (My past experience loading for .308s, suggested this 42.0-44.0 range should deliver good accuracy.) For the first outing however I decided to seat the bullets just touching and at a later date play with seating depth a bit more to fine-tune my loads.
I settled on 43.0 grains of Varget and CCI 250s. This load gave me an average velocity of 2657 fps with an extreme spread (ES) of 10 fps and a standard deviation (SD) of 4. Those ES/SD numbers were for a 10-shot chrono string. [Editor: Those are impressively low numbers, which should translate to very tight vertical at long range.] I might mention that loaded round runout on my Sinclair concentricity checker was .001" or even less. You gotta love that Lapua brass!</div></div>
While not .308Win and Varget, it is an interesting study comparing BR2 and 215M primers in a similarly sized case.
http://www.the-long-family.com/primer_study.htm
