200gr accubond 300win mag

baltz526

Handloader
Sep 25, 2005
1,074
8
here is my question, my model77 ss ruger 300 win mag shoots the AccuBond 200gr great at 75deg, it will shoot a three shot group touching.i'm using imr4831 cci mag primers ww cases. with cold conditions i get 4" groups with the apperance of bullet instability, slightly out of round bullet holes in paper.the point of aim stays stable.is this a primer issue, a powder issue, or a twist rate issue, with the long 200gr profile of the AccuBond. the powder is recent, and the primers have been stored in a sealed ammo can for several years.
 

bhruble

Beginner
Feb 5, 2022
5
4
The first thing I would change is to go with a Federal Mag Primer , hotter flame to better ignite your slow burning powder when the temps are colder , I think you'll see improvement !
 

SJB358

Ballistician
Dec 24, 2006
31,304
564
here is my question, my model77 ss ruger 300 win mag shoots the AccuBond 200gr great at 75deg, it will shoot a three shot group touching.i'm using imr4831 cci mag primers ww cases. with cold conditions i get 4" groups with the apperance of bullet instability, slightly out of round bullet holes in paper.the point of aim stays stable.is this a primer issue, a powder issue, or a twist rate issue, with the long 200gr profile of the AccuBond. the powder is recent, and the primers have been stored in a sealed ammo can for several years.

What's the difference in speed? Oblong bullet holes are a concern with a 1-10 gun and I have seen that bullet still shoot fine, at very low speeds with a 10 twist. I can't imagine you are losing so much speed in the cold it's going to heck.

Just my thought, but how many great groups did you get at 75 degrees to validate the load? I know IMR4831 isn't a perfectly temp stable powder but it hasn't ever been that sorta shifty in my use.
 

TXbaldhunter

Handloader
May 12, 2007
276
24
Winchester or Federal Magnum Primers are a little hotter.I've used a lot of CCI's,but I like the Win or Fed better.
 

SJB358

Ballistician
Dec 24, 2006
31,304
564
Winchester or Federal Magnum Primers are a little hotter.I've used a lot of CCI's,but I like the Win or Fed better.
Actually, from a recent run down a few years ago, that isn't true. CCI250's were the hottest.

Now, I hate sounding like a know it all, but when I tried 215's in place of 250's in a few of my favorite loads it verified what I was seeing. I think back when 215's were new stuff they were the hottest, but today, I believe 250's are the hottest ones out there. I believe it was John Barsness that did the test, but don't hold me to it.
 

JD338

Range Officer
Staff member
Nov 4, 2004
21,725
994
I would make sure the rings and mounts are torqued to spec. Why abo copper fouling? Does the rifle need a deep clei?

JD338
 
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