I have made several previous postings regarding loads for my M81 in .30 Rem. I did a few more tests today. As in the past, the firing was done from a bench rest over sand bags at a distance of 50 yards using factory open sights. Accurate Arms (AA) 2460 ball powder was used for all loads. AA2460 has weight-for-weight ballistic performance close to IMR4895 or IMR3031. Cartridge OAL was 2.52" in all loadings. For firing the following loads, five rounds were loaded in the magazine. The rifle fed and functioned properly for each of the following three 5-shot strings:
1. 110 grain Hornady 110 grain spire point bullet with 36.0 grains of AA2460. For a single five shot string, at 6' from muzzle the average velocity was 2562 ft/sec, with SD = 65 ft/sec. 50-yard group size was 2.5" (center-to-center)
2. 170 grain Hornady flat point bullet with 30.0 grains of AA2460. For a single five-shot string. at 6' from muzzle the average velocity was 2137 ft/sec, with SD = 26 ft/sec. 50-yard group size was 1.5" (center-to-center). This was the tightest group I have ever fired with this rifle.
3. This was the same load as #2 above, except 170 grain Remington Core-Lokt bullets were used instead of Hornady. Average 6' velocity was 2138 ft/sec, with SD = 20 ft/sec. The grouping was a little worse than #2, with the best four shots having a 50-yard 2.0" group size (C-to-C), with a fifth shot being a flyer that went low and left, increasing the total 5-shot 50-yard group size to 4.0" (C-to-C).
There were no obvious signs of high pressure for any of these loads.
It would take a lot more shooting to establish without a doubt that the Hornady 170 grain bullets produce better groups than the Remington Core-Lokts, so I can't speculate on that - except from what I know now, I'd use the Hornady bullets for hunting.