Norma URP 7mm-08

H

harveycmd

Inactive
I'm trying to find out if some have used URP for 7mm-08. I've seen some data on 160gr bullets, but I'm interested in 139-140gr. Given its burn rate, I would think it should be suitable, but I realize the chemistry of the powder may prevent this.

I'd be interested in hearing from anyone who has tried.
 
Ummm, your thinking of Norma MRP. Not URP.
Norma does not list data for URP in the 7mm-08.

I looked at the 2 burn charts that i have. URP is not even listed on them.
Use at your own discretion at your own risk.
 
Western distributes both URP and MRP in this country. Both Powder valley and Midway retail it, among others. URP is faster than MRP and lies between 203B and 204 in burn rate. So the burn rate is appropriate for 7mm-08, though near the slow end of the range.

So, why do you see the slower MRP listed for 150 grain bullets and not URP? The reason is the bulk density of URP is lower than MRP, so it is hard to get a heavy enough charge of URP in the case to reach normal peak pressures with either the 139 grain Hornady SST Interlock or the Sierra 140 grain SP without significant compression. The QuickLOAD computer model said 105% case fill was needed to get to about 55,000 psi. That exact number must be taken with a grain of salt, but it gives you a good sense of the issue.

That bulk is the reason this powder does better in the larger .30-06 case volume as suggested in the load data book. Even there, it does best with a 180 grain bullet (same sectional density as a 153 grain 7mm) or heavier. It would probably be good in a 7mm-06, if you decided to build that wildcat.
 
FWIW, I routinely load compressed loads of Ramshot HUNTER for my 7mm08. It has never been an issue and I have loaded up to 110% without a problem.

As to whether or not this is better than say, using BIG GAME which gives slightly less velocities but with the correct density for the lighter bullets I can't say. But I shoot 150-175 grain bullets in my 7mm08 so it's not a problem I run into.
 
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