Today I made my first attempt to form 375 jdj brass from 444 marlin brass. I have made 7x30s from 30-30s before without problems. I tried my usual steps, lubed with one-shot and mica in the neck but when I ran it through the sizing die, it just didnt want to go... at all. I put pretty good force on my press trying to make it size but I felt like if I pushed any harder the case was going to stick. What am I not doing right? These are hornady dies with good, clean brass on a rock chucker press. Any advice would be appreciated. Thanks, John

Im getting ready to do the same thing soon. I have read this try Imperial sizing die wax . Try this link to http://specialtypistols.infopop.cc/groupee/forums

make sure to chamfer and de-burr all the 444 case mouths first. If any of the 444 case mouths are out of round, you may get a collapse in the shoulder area as well.

Not to ask a stupid question, but are you sure the dies are for the 375 JDJ?

I've always used the RCBS lube to form this brass and have never had a problem. Also, like stated above, I make sure and chamfer prior to sizing.

I have been told to run it through a 44 or a 444 die to make sure the neck is nice and true also,
Thanks,Keith

Yes, the dies are 375jdj. I dont know what I was thinking when I said I was using one shot lube. What I was using is hornady unique. I've been using it for about 10 years and have never stuck a case. But it doesnt seem to be doing the trick on my 444 brass. Anyway, I dug around and found my old rcbs pad and lube just to give a shot and the case sized alot easier. I chamfered and deburred a few and ran them through and a couple of them started to split alittle at the mouth. I'll try running them through a 44 die to see if that helps. Thanks for all your advice fellas. I'll let you know how it all turns out. Thanks again, John

You might want to anneal the cases first if the splitting persist.
Jeff

I'm pretty sure One Shot is not for sizing cases like that. I have had trouble using one shot just sizing necks. Go with RCBS liquid lub and a pad. I've never had a problem with my 375jdj or 309jdj
I roll the brass on a pad with RCBS lube and put some inside the neck area with a q-tip. It does take some presure but they always work.
If you need some formed brass let me know to get started. I have some extra that has been fired a few times. Just run them through your dies and load so they will form to YOUR chamber.

Mike

On these cases, I found that you must first true them up in a .444 die (or anything similar) so that the case mouths have any dents and rough spots ironed out. After that, the problems magically go away.

Also, I've used Hornady One-Shot for necking down the .444, and it works just fine as long as you have a smooth, tapered expander. Most expanders do require a little polishing to get them to perform best.