300win mag 190smk and 180accubonds

Joined
Nov 28, 2009
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1,101
Location
Thatcher arizona
Went out again with the 300 win mag. tried some 180gr accubonds. I think I ended a bit high as the groups started spreading, so they prefer a certain velocity window? But the first and second were both right around an inch and plenty of speed. The n560 was giving damn good numbers as far as I’m concerned. Then shot the 190smk and h4831sc and the numbers continued. I’m going to work the 72.5gr load some. I know only 3 shot groups. But it gives me a solid start point for this rifle.
mall but 1 load I tried gave me single digit es/sd the one that didn’t was 10sd and 20es. Can’t load the videos. But here’s the target. I circled groups and marked them.
the left one I circled was 72.5gr h4831 190smk
Ave-2916fps
Sd-3
Es-5
The bottom left circle was 74gr n560
Ave-3049
Sd-4
Es-9
I’m going to load the same ones again and mess with seating depth some. I also redid the first load that shot well of 70.5gr h4831sc with the 190smk
Ave-2863
Sd-6
Es-12
I think I’ve got some good starting points to play with.

IMG_6232.jpeg IMG_6228.jpeg IMG_6223.jpeg IMG_6225.jpeg
 
Thank you for taking the time to share this. I have just a few comments.
  • Looking at measures of variation (i.e., SD & EV) with small subgroup size (as n = 3 to 9) has very low confidence level. Looking at the average speed is helpful in seeing if you're approaching the published maximum speed (in order to get an idea if you are approaching max and dangerous pressure). But that's about all that looking at avg. speed is good for, at this stage of the game. When starting out, I only do subgroups of 3. also. As I find one that is potentially accurate with no obvious overpressure signs, I will then repeat that experiment using 5 in a Subgroup and 2 other sets of 5 with sm changes in charge weights on each side of that sweet spot. After that time, also, you can more or less jump to the lands As this will usually only allow a small improvement in accuracy/precision.
  • Prioritize your objectives. Write them out (w/ priority) on top of your working paper/log sheet.
    • For example, for me,
      • #1 Precision within 1.5 MOA (for =< 4.5 inches at 300 yds. for big game) ,
      • #2. Use large for calibre, non-lead bullet,
      • #3 Min. muzzle Speed to achieve >= 2000 ft-lb at 350 yds to penetrate >= 36 " for thru-n-thru shot on elk, and to mushroom >= 1.5x.
  • I'd only measure and make decisions on the max vertical distance /stringing within a subgroup. (The causes of variation in horizontal POI grouping is: 1) wind and/or 2) you.
  • Only use one brand of case within an experiment. "Headstamp" is another variable.
Have fun and stay safe!
 
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