Got the Marlin 336C back yesterday. I had sent it to JES Reboring to be opened up to 38-55 since the bore was in bad shape when I bought it. Jesse's turnaround is real quick compared to most, 3 weeks including a week+ each way for shipping. His work is every bit as good as his turnaround. He gets some flack from some of the traditionalists since he uses a .366 bore,.3755 groove, so you can use modern jacketed bullet. The original specs were for .377-.379 groove. I have no plans at all for jacketed bullets in this rifle, so didn't really care which way it went.
I had cast some Lee 38-250RF bullets while waiting on the rifle, PC some, pan lubed others with Winds Wonder Wax(5 parts bees wax, 4 parts Crisco, 1 Part Vaseline). Had loads made up with both at 9 grains Unique and 10 grains Universal.
The rifle came in yesterday and even though the temperature was in the high 90s, working up to 100, I had to give it a try. Mounted an old Vari-X III 2.5-8 for load workup and setup at 50 yards in my backyard.
The two loads with PC didn't work bad, both Unique and Universal turned in nice groups.
10gr Universal-Lee 250
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9 gr Unique-Lee 250
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The pan lube didnt do quite as good, wondering if it was the heat.
Got out this morning while the temperature was still in the 80s and tried 10-Unique with the pan lube and got 5 in under an inch, take out the fouler and it had 4 in half an inch. Don't know if it was cooler temps or better concentration on my part.

Loaded up some with 28-3031-250-Pan Lube and I'm guessing I found my target load.
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Freak group I'm sure but it got me thinking about leaving the scope on for a while!
Alternated back and forth with pan lube and PC and all groups were 5/8 or under. Velocity was 1362 with the pan lube, 1417 with the PC
I still want to try some 4895 and some loads around 15-1600fps, but I could stay with the loads I've already tried for most anything I'll ever do with it.