My brother has a #1 in 300h&h. He's using 168ct's or 180 hornady pills in his rifle pushed by rl powder. You'll only get three to five firings with full power loads as the heavy taper stretches the brass a bit more than the newer designs. Think 300 wsm
or 300 win power level wise. Some 300h&h rifles are rather short throated so measure up before you load rounds.
Win is offering a couple of the m70 variants in 300h&h this year... marked 300HH on the lists.