Originally Posted by harfman99
I was doing some load workup this last week and found the one. The load 180 berger vld 84 grains of retumbo fed 215 primers. fired and annealed rem brass. The load gave me 3283 avg with a average diff of 8 fps and gave me .25 moa at 600. The brass was handling it very well no signs of excessive pleasure at all and i couldn't have been happier. I went out with my brother Friday evening and had problems with over pleasuring cases. It was only about 65 degrees when we were out and only about 10 warmer than it was when i did the load workup. so temp shouldn't have been the problem. All cases had a had a normal going through neck and mouth cleaning and partial neck sizing, primer pockets also cleaned. the powder scaled out to the 10th of a grain and from the same jug.
bullets were all set out to the same leignth. the bullets are just touching the lands.
I don't know what i am doing wrong to cause such a big diferance in preasure. Would it be the barrel the brass of something i am overlooking.
also the problem wasn't continious with three over preasuring and the next round not and several more after that and back and fourth. I put 12 rounds down range that nite and kept the shots spread apart to keep the barrel cool.
any thing else to look at would be greatly appreciated.
3284 fps with a 180gn Berger out of a 7mm RUM is over the edge unless you're running a 30" barrel? Out of the usual 26" barrel even in the sloppy factory chambers with the long throat 3200fps is about maximum.
If you're right on the edge pressure wise, the carbon build up and slight throat roughening as you fire progressively more rounds can push you over the edge, especially if the temperature is warmer as well.
Case length can be an issue, but most factory RUM chamber lengths are 2.875" or longer. Even a tight custom chamber will usually take brass 2.870" long with out spiking pressure. Don't trim until you've actually measured your chamber length, or you may trim too much.
Don't be put off the RUM, so long as you don't run it over the edge or expect to fire large numbers of rounds through it in rapid succession, it'll give superb long range performance with managable recoil that is hard to beat. I have built many 7mm/404's and 7mm RUMs and have never found them a problem to load for. I use mainly 2218/H50BMG powder and anywhere from 99 to 104 grains with the 180 Bergers and 175 SMK's depending on throat length. I have always got good barrel life when used in big game hunting situations. They are not varmint or match rounds, but a 180 Berger at 3200 fps out of a 26" barrel is a pretty darn good long range hunting performer!