Have just tested CCI and MUROM large rifle primers side-by-side in identical conditions.
260 rem, lap brass, 46g of N560 Temp 65 -70f, Humidity 60%, DA 1200 FT
I fired 2 x 5 shot groups of each primer....both will group .5 moa.
Now for the differences....
1 The CCIs produced some awful ES results.....77 & 44 for the 2 groups. 2 The Muroms cut this by 50% ! 3 The CCIs showed 48fps MV difference on the averages of the 2 groups. 4 The Muroms showed 1 fps MV difference on averaged velocities of the two groups!
Given that each group showed MVs in the upper 2800fps range I was sutprised to find that the Muroms print .5 moa higher than the CCIs.....down to barrel harmonics I guess......the Murom groups were very consistent.
I am transfering to Muroms and cutting primer costs by about 2/3rds.
Rich H......if you read this I would like to add 3000 Muromsto my wishlist.
The CCI with the awful ES and the Murom with their outstandingly consistent ES still group <.5" according to the after action report above.
It would appear to me that there is something else that would equate to good consistent rounds other than ES as both large and small ES still manage to group the same. Even a huge spread in average MV gave very similar grouping to the much tighter MV spread. I sometimes think as reloaders we get too worried about SD, ES and MV.
Now a 2/3 saving on price would make the decision between two primers that give the same results where it matters, at the target, easy.
Murom £29/1000 and more consistent CCI BR £85/1000
No brainer really.
Also, whilst ES might make no difference in groups at short range, it makes a big difference at extreme range (1000yds +). 77fps difference in velocity is a difference of 2.2moa at 1000yds, 5.2moa at 1500yds. That's a massive difference.