300 rum load help

[djtjr]

Guys for those of you loading for the 300 rum or other hot overbore cartridges I have some questions. I built up a load settled on 93.5 gm of retumbo under a 200 accubond in rem brass and a 215m primer with the bullet seated to mag depth. A few weeks ago I built up in .5 gn increments from 90 to as high as 97 before starting to see pressure signs ejector marks flat trimers etc. I settled on the low node and took it out yesterday just to chrono it for a upcoming hunt to start building my click chart. In similar temp weather as the last excursion I blew the first 3 primer clear out of the case with some other signs of presure but not much. It was only the 2 nd or 3rd firing on that brass so would it be customary to get loose primer pockets after 1 firing any other thoughts? Is there a better brass option? How many firings are you getting out of your mag brass. Any other thoughts welcome.
Thanks
Don

 

[djtjr]

Re: 300 rum load help

noone have this issue in any magnums before?

 

[bohem]

Re: 300 rum load help

I don't own one, but I have a few friends who do.

The things that I've learned on the 300 RUM:

The brass is poor from the factory, and the action that it is placed in is a bit on the small side for that case. The loads involved in firing are significantly higher than the 300 WM case design (which was one of the driving criteria of the receiver design).

Blowing primers suggests a couple of things, but one of them oft left unnoticed is the amount that the first firing of the brass deformed the primer pocket.

You can shoot a hot load, grow the case head, and it will appear to be OK on pressure. Second and third loading of the case and it will show pressure signs.

This is not a problem common ONLY to magnums, but a lot of people tend to overload the mag cartridges before noting pressure issues.

This is usually due to the extra material in the case head and the tendency of the brass case head to soak up some extra PSI before sneezing.

 

[esorensen]

Re: 300 rum load help

Bohem is right. The 300 RUM brass from Remington is VERY soft. If you've ever prepped and trimmed any number of cases, you'll know what I'm talking about. Warm to hot loads will get you about three firings and the primer pockets will be too loose. I don't think the brass is a good indicator of how much pressure there is in a given load, as the brass is so soft. If the cases were by some other manufacturer, the same loads would give much longer brass life and no "pressure" signs, even at the same relative pressure.

I rechambered my RUM with a match reamer that was a bit tighter with little headspace. I thought that might get me a couple more firings from the brass, but it was not to be. Rem brass sure preps nice and quick though.

 

[djtjr]

Re: 300 rum load help

thanks guys
d