I just took delivery of a Lee Collet die set. I ordered a 300 RUM and recieved a 300 Weatherby.

The instructions say 300 Weatherby but the die itself is stamped "300 MAG G5". Where this is a neck sizing die is it possible that this will work on the 300 RUM?

Anybody know one way or the other or care to guess?

I wonder if they use the same die for both and I just got the wrong instructions? I guess I might as well try it before going through the pain of exchanging it by mail.

I'm not near a source to look up case dimensions right now. I'm pretty sure the Weatherby is shorter overall and has a longer neck....

(edit) I also received a Lee Factory Crimp Die for the 300 RUM and I just noticed that the die itself is just stamped "300 MAG H5". This gives me a bit of hope.

The Rum is only .025" longer. If you think you got the wrong die from your supplier I'd get back to them. If you got the wrong die inside the yellow plastic holder I'd get a hold of lee. They are easy to find onthe internet.
I have one for my 300 wby and it isn't working well. It binds on the case as the case enters the collet and won't let go real easy on the way back out. I spent some time yesterday and can't figure out why it is doing that. The collet has plenty of room to slide the case in and out when it's out of the die. It's almost like the collet is going into the cup the closes it as the shell is still going up into the die?? Oh well.....I've got my forester dies making really really good runnout anyhow.

Thanks kraky.

If you get a chance could you check your 300 wby die and tell me what is stamped near the bottom edge of it? If its the same as mine I may be ok. .025" is fairly close.

I think I read that the collet needs to be lubed sometimes, you may have already tried that.

Well--this may add to the mystery....mine says 300 mag B4. If I remember right when I had the cup out of the top ofthe die it just said 300 mag.
Lee sent me a new cup but it didn't change a thing. The collet seems open enough to slide a fired casing into. I just can't figure out the binding. And.....yup....I tried some lube in the collet.
I found that in the gun I own...only the mildest loads would chamber after a collet resize without some resistance on the bolt. I did an experiment with ammo made with the same casings and exact same loads of those that chambered with the slightest resistance and those that chambered free. I found a pretty significant change in point of impact....like 3" at 100 yds. Both grouped good but the change of impact really bothered me. So, I bought a redding body die to use after the collet die. THEN a light went on in my head that I was being crazy and might as well go back to full length sizing.
Funny how one can chase his tail in a circle at this game of reloading.

It is entirely possible that the Lee Collet die is the same for both the .300 WBY and .300 Ultra. It is only the mandrel and the neck portion that matter, so the lower portion of the collet "body" needs only be something larger than the body of the case. Thus, if two cases use the same diameter bullet and are approximately the same length in the base-to-shoulder dimension, then the same die could conceivably be used for both.

Along those lines, I use a .223 die for .222 Magnum by utilizing a washer of the right thickness placed on top of the shell holder head to compensate for the difference in body lengths.

It turns out the answer is NO.

I just tried it. The case body on the RUM is way too fat. It only made it about halfway into the die before binding up on the mouth of the die.

I guess I'll have to talk to the outfit I bought it from. Its hardly worth returning for the price of it. Maybe I just need the collet part. I think I'll contact Lee too.

Thanks a lot for the input guys. I'll let you know what happens.

STONECREEK.....YOU WONDERFUL PERSON!!!

I thought about your idea on the washer. I looked closer at my die and saw the sleeve that contacts the shellholder is getting peened over from use. What was happening was the casing was going too high into the die and the collet was grabbing on the beginning of the radius of the neck and trying to size it. Obviously it couldn't do that without binding.
I just got home from the hardware store with a .094" think washer for the top of the shellholder and......problem fixed. The sleeve now "activates" the collet befor the casing is all the way into the die.......YIPPEE!!

Ain't it great what a discussion can produce?