07-01-2020, 05:26 PM
I found that my Howa 6.5 Grendel required an extended break-in of about 100 rounds, with frequently cleaning. Once I did that, my groups closed up quite a bid. My best combination was with Hornady 123 grain ELD bullets, Hornady cases, CCI 400 primers, and 29.5 grain of Alliant Power-Pro Varmint. This is a warm load that did not show excessive pressure signs. I did achieve 2555 fps average, with SD in the low teens. Groups were between o.4 and o.7 inches at 100 yards. It also liked the Lapua Scenar 123 grain HP, but with a smaller charge: 29.0 grains of Power-Pro Varment. The velocity was still 2550 fps average for most strings. The ambient temperature was 95 degrees. When I tested this round at 50 degrees F. the veocity fell about 60 fps, and the groups opened to just under one inch. Also, the rifle tolerated a long cartridge length with Benchmark and H322 (group size between 0.7 and 0.9 inches at 100 yards), but not with Varmint. I had to seat the bullet back to COAL: 2.250"