Thoughts on these targets?

mmattockx

mmattockx

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Rifle is an AR with McGowan match barrel chambered in .223 Wylde. Powder is WC735, bullets are 69gr SMK's for loads #1-8 and 69gr PRVI BTHPs for #9-10. OAL is 2.250", range is 100m, shot off a front rest and tail bag. The grid on the paper is 1" square.

Loads #1-5:
20170304_120249_zps7r4hkuzq.jpg



Loads #6-10:
20170304_120220_zps3ag3gzui.jpg



22.8gr is clearly the winner of these, both with the SMK's and the PRVI's (loads #5 and #9). I am going to try some at 22.9gr as well to see if things can get any better, but it is already pretty damn good. Load #5 measures just over 0.250" and several others are well under 1".

Questions:

1) Should I be shooting 5 round or 10 round groups to verify what load #5 is really shooting? Shoot the whole string at once or let the barrel cool a bit through the string?
2) It was ~7C yesterday when I shot these, should I expect to have to tweak the load for summer temps to stay on the node? I have heard that WC735 is temperature sensitive, but how sensitive? The load is nowhere near max, FWIW, with nice rounded edges on the primers and no other pressure signs.
3) Anything else to try for tweaking to improve the load?


Thanks,
Mark
 
I'm kinda paranoid about going 3-shot groups. If I had the rifle on a lead sled, perhaps, or in a fixed vise that makes sure it cannot move and that's I'm out of the equation... it's too damned easy to twitch or jerk and voila, the three-rounds groups is discarded because it's not tight enough.

I think most people use 5-round groups. I often do also, but what I really prefer is to shoot a 10-round group, measure it and then measure it again with the best 9 holes. Those are 100m examples:

Loads%201621-22-23_zpskhefr1w5.jpg
 
OP, do you have access to a chronograph? I would put load 5 plus a couple of 0.1 gr increments up and down over the chronograph. What you are looking for is consistency of velocity - that is, where the curve flattens out for a couple of groups. This means you have a load that is tolerant to small differences in powder charge variation with little velocity variation. Hopefully that gels with group 5 and you're done.

I would also shoot 5 shot groups for better validation of group size and velocity stats.

Looking pretty good!
 
Shooting five, three shot groups, has shown you absolutely nothing about what you and your shooting.
Shooting about forty, five shot groups would give you some indication of your shooting, unless you let the barrel cool during the shooting, in which case nothing is shown about accuracy of your outfit.
 
Grawfr said:
I'm kinda paranoid about going 3-shot groups.
Click to expand...

More testing will be done to confirm that #5 wasn't a fluke. I was shooting 3 shot groups just looking for the best choices to look further at. This was the second round of loads for this rifle, looking at loads around the most promising initial tests.

Anybody have any experience on how temp sensitive WC735 is and if I am likely to have to tweak the load a bit for summer?


Mark
 
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