7mm Rum Loads

[Pivot Buster]

Well I'm new to this forum thing and this is my first post so bear with me. I just received my new 7 rum from Proof Research. 26" barrel 1:9. I'm looking for a little loading insight. Now I know Retumbo seems to be the powder of choice for most but we just can't get it these days. The powders I'm playing with are vv n560, vv n570, vvn165. Brass nosler custom, bullet 160AB, primer F215m. 87 g of vv n560 was giving me 3400 with extractor signs of pressure with a still smooth bolt operation. 4 shot round was withen 6 ft sec of each other and were all touching. This was in fresh brass. Reloads in those same cases at same specs the next day jumped up 77 ft per sec with higher pressure signs. Whats your thoughts? No I didn't mess up on powder amount, oal, primers. Switched to vv n570. 93 g 3350 two 2 shot groups both pairs an even inch appart with light pressure signs. Speed separation was averaging 15 to 20 ft sec differance. the grouping and speed are less than desirable with this slower powder. The grains are so big on the n570 that breaking them may be a must for consistant speed again whats your thoughts? I thought we had it pegged with the n560 until the reloads. I could creep up the loads on the n570 to signs of solid pressure and hope accuracy comes around. I just don't know. Does maximizing case capacity create a more consitant round? N560 leaves room in the case where as n570 is almost getting to the top. Any insight and or advice would be greatly appreciated. We only have the VV powders to work with so switching to something else is going to be hard with the current demand. If I keep messing around with this thing I'll have the barrel burned out just in time to go hunting. I just can't help myself though. LOL. I want these groups tight and my speed consistant so I can get my turrent cut. Thanks in advance.

 

[Lefty7mmstw]

I think your pressure may be a bit warm if you are hitting over 3250-3300 fps with 160's in the 7rum. I ran one for a few years with 140 grain bullets doing 3500 fps and 175's doing 3100 fps. My brother has a 7 rum at present doing just shy of 3400 fps with 150 grain pills. They were/are both 26" barrels and pretty close to topped out. I was using rl25 with the 140's and I 5010 with the 175's; my brother uses retumbo with 150's.
With this cal. and 160-175 grain bullets I'd really be looking at some of the powders for the 50bmg. They would get you your speed without being quite so flaky. They would also give you good case fill, which in a case like the 7rum is **** near manditory.