Velocity vs. powder charge

[imq707s]

Over the last few weeks I've been doing some load development for my Ruger Mk-2 all-weather rifle in 7mm Rem Mag. I'm using Hornady's 139gr. SST bullets, and H-4831 powder. I've worked up loads from the recomended starting load of 62.8 gr. of powder up to the max of 67gr. of powder. I've found two loads that work the best. 64gr and 66.5 gr. of H-4831. I can get consistant groups of around .75" with both of them. Here's my quesiton, what is the approximate difference in velocity between these two loads? If they are both equally accurate, which one should I use, the load near the bottom (64 gr.) or the load near max (66.5 gr.)? Is the extended barrel life and less recoil of the 64 gr. load worth the slower velocity. I normally target shoot and deer hunt with this rifel. Any info would be great.

 

[Art Eatman]

Don't have a loading data book handy, but I'd just use book numbers for a baseline and interpolate between them. For government work, just assume a straight line of velocity vs. charge weight.

As an arbitrary example, if 62.8 grains gives 3,000 ft/sec, and 67.0 grains gives 3,300 ft/sec: I'd just assume that 65.0 is about halfway, so the velocity is about 3,150. That's close enough as makes no nevermind.

Unless you just need the absolutely flattest trajectory out to a 500-yard Bambi shot, I wouldn't worry about the trivial bit of difference in velocity between the 64.0 and the 66.5 loads. Bambi won't know the difference.

And I'm gonna move this to the Reloading Forum.

, Art