Blame it on the season, but sometimes i just like to remember...think looking at the Christmas tree kicked this bout of memory into gear.
Had a buddy that ran a commercial reloading biz. in the early 1980's; he trusted his idiot son to order powder. Ended up with a crap-load of 4320 he really didn't want. He offered me 40 pounds of it at dealer invoice (and 10,000 well stored Alcan small rifle primers as well 600 53gr. Remington .224" match HP's).
Ruger #3's were still new at the time, and i picked one up in .223. Not giving a loading recommendation, but I do not think you can get enough IMR4320 under a 53gr. bullet in a military .223 case to cause an over load. (not don't just go and do it...some clown out there will probably pre-compress the powder with a arbor press.) Out the box, with just a 2-7X Leup. on top, fired two 200 meter 5-shot groups, one at 1 .26" and the other at 1.57", with a dinky little singles shot, barrel band, carbine and a 7X scope.
kind of sold me on the combination.
So a HK SL6 comes along (not sold for long...an odd looking semi-sporter semi-auto that looked more WWII than 1980's). Same load produced 10-shot 100yard groups in the 8's.
So i tried 4320 in everything using a standard case from a 375-06 on down (don't include the belted mags) and they all shot at least decently....a few had one or two loads they shot better, but none of the rifles tried "hated" the powder.
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Idiot son. About 4 yeas later, Mr. IQ decided to get rid of the old Christmas tree by jamming it into the fire place. Burned down both the house and the Ammo Shop.