300 rum help

[djtjr]

Guys for thousand 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

 

[highridge1]

All the same lot of powder? I had issues with retumbo and H1000 varying too much lot to lot ,so I went back to RL 25 in my 300 ultra and 338 ultra and every thing went better.

 

[trebark]

Generally speaking you should get several firings from your Remington brass. I shoot Nosler brass (which is notoriously soft) in my 300RUM and I'm on my second loading and seem to be doing fine.

Did you keep track of the brass that had the 97grains of powder in them? you may have loaded them for the second time and they were already loosened up a bit.

 

[J E Custom]

If the primers are easy to press in they were probably some of the "Hot" loaded brass and the
primer pockets expanded .

Moderate loadings should last 4 or 5 times, but heavy loadings may only last a couple of times
before becoming trash.

While loading if the primer goes in with little or no effort that case is rejected and if there is
very many they are all rejected.

The main reasons that you should blow a primer is pressure (Which may be caused by many things)
or a lose primer pocket caused by many other problems.

J E CUSTOM

 

[venom600]

I've been doing load development with the same 100 pcs. of brass for the last couple of months. Some of the pcs of brass have been loaded 4 times now. All are holding up so far.

Pet load so far is the 200g Barnes LRX over 96.5 grains of Magnum and a Remington 9 1/2 primer. Getting 3207 avg muzzle velocity and no pressure signs.

--Ben

 

[lamiglas]

A friend of mine had this same problem. he was doing load development on a 338 rum and loaded up some new brass for load developement/ pressure testing. he didnt realize some of these first loads were over pressure until he loaded them the second time. at this point he learned that some of the higher pressure loads that he had shot resulted in very loose primer pockets.

 

[djtjr]

Thanks guys I appreciate it. All these answers seem consistent with my thoughts as well

 

[sureshot300]

Make sure your cases are trimmed to length properly. I wouldn't think you would have excessive case stretch with load of Retumbo, but just something to check.

I would suspect loose primers or lot of powder as well. Verify your overall length again too.

Don