Florida Shooters Network

I’d like to know how much less powder should be used in 7.62x51 cases using 308 specs.I use 43.2g Varget w/68g Hornady match in my 308 hand loads.A buddy told me that he thinks it’s 10% less. But he’s never hand loaded 7.62 x 51.So I’d like a second opinion if anyone knows ,thank you.

I don't know of any "rule of thumb" on charge reduction. However my Hornady Book recommends a minimum 3% reduction in charge when using mil-spec brass over commercial brass.

That said the right thing to do would be to start at the lower end of 308 WIN load and work up in increments checking your results with a chronograph. I usually load about 3-5 rounds of each charge with each batch being about .5 grain apart then check and record accuracy and velocity. Keep in mind that your OAL will also effect your results. I like to gauge my chamber and use about a .010" clearance from the olgive to the rifling to determine my OAL.

It all depends on that you are loading and for why.
For hunting or target loads, I go through the brass and select brass of the same manufacturer or head stamp/date, and use a long established load data.
For plinking, I just load to the starting load listed in the manual, and ignore who made the brass.
For mass loading to be fired in a MG, I just load what brass I have on hand, half way between min and max load; and feed them through the Dillon, with overall length set just under max.
Never had any issues doing the above.

I am going to load some at the recommended starting load and work up from there.I am going to be shooting these through a bolt action CZ 550 varmint.Purpose is target shooting.

3 percent reduction is about right. as far as I can determine, the real differences in pressure specs between the two landings are negligible and arise from CUP and PSI not corresponding in a linear fashion. Unless you are shooting something that may have a weaker action like an Ishapore Enfield or a small ring Mauser converted to .308, the only thing you need to worry about is whether the missus cases have less volume than commercial cases. You can determine this by weighing your milsurp cases and comparing the weight to commercial cases. The heavier case will have less volume.