H4198 for .308 WIN loads

[andym79]

Hi guys, I have had a lot of success recently using H4198 16gns in my .30-30, behind a 165 gn cast bullet. I am thinking about doing the same for my .308 WIN. The Lyman manual lists the same bullet with 24 gn of IMR4198!

Here in lies the problem, here I can only get H4198 and not IMR4198! Hodgdon listed a load for 160 gn cast bullets using H4198, they do not however list such a load for cast in the .308 Win. On the basis of extrapolation (case capacity, and a ratio between recommended H4198 (starting 15gns) vs IMR4198 (starting 18gns) for the 30-30) 16 gns in the 30-30 would be around 20 in the .308, but I don't want to just guess at it. Has anyone used H4198 in the .308 WIN?

I know IMR4198 and H4198 are not identical are they similar enough at reduced loads?

[303Guy]

Hodgdon show the two to be similar but H4198 seems to be a little slower and denser requiring a slightly higher load for the same velocity. This in several cartridges including the 30-30 and 308 but with lighter bullets.

[Larry Gibson]

Start at 18 gr with either H or IMR and use a 1/2 - 3/4 gr dacron filler. Work up from there in 1 gr increments until accuracy goes south. Then tweak the most accurate load 1/2 gr + and -. Preferably use 10 shot test groups.

Larry Gibson

[runfiverun]

bumping up the load for the 308 from the 30-30 would get your pressure back to the same.
the 30-30 is 2.4 cc's of case capacity and the 308 is 3.4 cc's.
the powder wuld still give you the same gas volume using the same load in both.
much like using 17 grs of 2400 in both and the 0-6 also.
there will be some small differences because of the chamber size but everything else being the same, boolit weight and bbl length, you would see quite similar velocities.

i think i would just use the same load but add a filler for the 308 and work up from there till i was happy.