Re: 7RUM 30\" barrel velocity potential?
Realistic comfortable loads should get you into the 3050 to 3100 fps range with most barrels. Some will be slightly faster, some slightly slower. That is with the 200 gr ULD RBBT.
When I say comfortable loads I mean you can get 5 firings per case before primer pockets begin to loosen up.
The 7mm RUM is a great round with the heavy 7mm bullets out now.
Twist wise, a 1-8.5 would probably be about perfect. That said, I have a 1-9 6 groove Lilja on my 27" barreled 7mm AM and get 3150 fps and have not had any stability issues. Others have said there were issues with the 200 gr ULD RBBT in a 1-9 twist barrel.
For that reason you may want to go with a slightly faster twist.
Keep in mind, if you want to use the 200 gr ULD RBBT, stay away from wide land rifling designs. The 3 groove barrels are pretty hard on these bullets, a 6 groove seems to be just the ticket to get the most velocity for the money.
Rock barrels has made me a prototype, thin land barrel in their 5R design which I have been testing on my heavy 7mm AM. It has been working perfectly so far with velocities up to just shy of 3300 fps. THis is a 1-8.7 twist so you may want to contact them for the same barrel in perhaps a 1-8 or 1-8.3 as they can make any twist rate you want in 1/3" steps.
Simply put, these big bullets in a long barreled 7mm RUM really turn that chambering into a different beast!!
You would not be unhappy with its performance at long range.
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