Has anyone else experienced this? A wide ES with Retumbo? Briefly, here's what I have and have done yet I still get extreme spreads of 30 or more; never in the single digits.
100 pc of Hornady brass divided into boxes of 20 with 1 to 4 firings through each lot. All cases were trimmed to the same length after the first firing and none has exceeded .010" over that length since then. After the first firing all the necks were turned to the same thickness, .013." Most needed only a partial turning to achieve this and any that needed more than about 80% are not included in the boxes in question. Flash holes were reamed to be uniform. And before reloading, the brass is cleaned with a tumbler and SS media.
I FL size to move the shoulder back .0015 to .002" and use a neck bushing to achieve a neck tension of no more than .002," usually a .307" or 308". I don't use the expander ball.
All reloadings have been 71 to 73 gn of Retumbo powder with 72.6 being the lowest ES (28) and has shown to be the most accurate without pressure signs.
CCI-250 primers and Berger 168 VLD Hunting bullets;the bullet seated .020 off the rifling. (Seating determined using a method written about by someone at Berger and posted elsewhere here on LRH.)
Bullets are sorted and seated as shown in Shawn Carlock's video so thet the OAL - may vary but the base to ogive dimension is within .001". The necks are brushed and lubed similarly too. After the first firing of the cases, concentricity is usually within .001" of both cases and assembled ammunition.
The rifle barrel is a Hart, 26" 1/9 twist and the remainder of the rifle has had all the customary squaring, truing, bedding ect. The rifle is a Remington 700 in 7mm RM.
I couple weekends ago, I shot the last of the batch where I has the ES of 28. I've reloaded 20 the other night and yesterday I fired 5 through the chrono (CED M2
) and the ES of those 5 was 67. I stopped right there. Routine was my norm; 1 shot every 5 minutes or so after 2 foulers (not counted)
Now here I am trying to figure out what's going on so I could adjust but my head has cramped. Anyone have any ideas?