I have a pre 64 M70 in 300 &H
It really liked this load. Mind you these are not the meaningless three shot groups you see all the time in magazines and the web, I prefer ten shot groups to determine consistency. The first is a nine shot group at 100 yards, and the second is a ten shot group at 300 yards.
I am going to recommend that on the first firing of your cases, you lubricate them and fire them lubricated, such as I have done:
The reason for this is that the base to shoulder distance of Belted Magnum cartridges was never standardized. What was standardized was headspace off the belt. You fire a dry case in a dry chamber and you will experience short case life.
If you want your cases to be ruined , like the reloader who shot these,
Just ignore my advice.
Since these cases are $2.00 each, I prefer to be financially prudent and extend their lifetime by first of all, on first firing, lubricating the cases. As I explained here:
Setting Headspace With a light coating of lube, like case lube, the front of the case not adhere to the chamber during combustion. So, instead of the side walls having to stretch to the bolt face, because the front is fixed, a lubricated case will slide to the bolt face, and the shoulders will fold out, creating a stress free, perfectly fireformed case.
When you resize the things, you are going to have to buy a special case gauge made for belted magnums, such as this Wilson Cartridge Headspace gauge sold by Midsouth.
https://www.midsouthshooterssupply....ilson-adjustable-case-gage-300-h-and-h-magnum
And again, this is because the base to shoulder distance for chambers and sizing dies was not established, and without these gauges, you will, and I mean will, push the shoulder too far back, and that will again, will cause case head separations. You set up these gauges using a fired case, and then you adjust the sizing die so you only bump the shoulder 0.003" or less. I do not recommend a 0.000" adjustment as the next firing the brass may be work hardened more, and then the case may stick during extraction. Your rifle has an extractor that was built around the assumption that the case contracted enough after firing that it did not have to yank the case off the chamber walls. Do that enough times and you will break your extractor. Start with the proper case clearance before firing, and end with the proper case clearance after firing, and both your cases and extractor will last longer.