Shooting my CZ 550 FS in 9.3x62 Mauser today I gathered some performance data and was a bit surprised:
Prvi Partisan 285 grain loading yielded 2138 fps average with extremes of 2121 and 2152 fps (10 rounds fired).
Lapua 285 yielded 2195 average with extremes of 2175 and 2210 fps (only three rounds fired).
Handloads using the Privi Partisan 285 grain bullet and 51 grains of H4895 averaged 2052 fps; extremes=2024/2069 (ten shots).
Handloads with 52 grains of H4895 averaged 2123 fps; extremes=2108/2136 (ten shots).
I'll be proceding by one grain increments as testing continues.
(Handloads showed no high pressure signs in my rifle, but you should always work up from published reloading guides, rather than depend on the web.)
I have NECG peep and red dot front sights on the rifle and shot at 100 yards. There's no good way to determine accuracy of the different loads without a scope (or much better eyesight), but each would produce groups of about 4". The Lapua shot about an inch higher at 100 yards than the Prvi.
Getting the correct height front sight for the NECG rear peep is tough. And they're expensive enough not to buy the whole set, so when I replaced the brass faced one that I couldn't see with a red dot that I could, I measured and ordered and it was just a tad too short. The fix seems to be pretty easy - I'll file a bit off the threaded part of the peep shaft so it will go down another complete turn and that should put me about two inches high at 100 yards with the Laupa, one inch high with the Prvi - about what I wanted.
As far as the factory ammo goes, Prvi averages about 57 fps slower than the Lapua. Doesn't seem very significant to me considering the cost difference.
-Don
