Benchmark is slow, you will never get there.
N133 with a thick cup primer in Lapua brass is the key...accuracy is astounding to say the least.
I'd rather run a 22-250; even get risky with a 225 Winny or 22 Zipper/Wasp.
What, by chance, is a "thick cup primer"? IME its a Rem. 7.5 or mil-spec CCI. Benchmark is too slow?
The AI 223 and 222 Mag will run close enough without magic primers, powder, cases and custom chambers for the latter. Better yet, magical pressure limits are not really needed either. Benchmark and slower fuel at above SAAMI spec is too slow?
Running 4,200 from a 223 begs for a larger case, and they're out there.
Am waiting to see recommended loads for 50 grainers at 3,850 from the std. 223 case now...the 22-250 is obsolete.
