My load development hasn't been going as well as expected since installing a new Criterion 26", 8 twist in 223 match barrel, and it occurs to me that maybe I'm just doing it wrong.:o
So I am hoping that I can beg some help from you guys with the "gray haired" load development skills, as plainly, mine suck!
I tried out the 77 TMK at the range yesterday with very good results. I'd decided to use IMR8208 for my loads because it was was near the top of the velocity list in my Lee loading manual, and experience tells me 8208 is fairly temperature stable.
Using the Lee manual, my loads started at 20.5 gr and 2535 fps (SG of 1.46) and topped out at 23.5 gr (a tad over book) for 2830 fps (calculated) and SG of 1.50, and were set to touching lands.
I shot 3 shot groups in round robin fashion at 200 yds, in conditions as follows: 100 F, winds 220 relative, 6 to 12 mph with gusts to 15. The range is fairly protected, but winds still matter. SG's were above as calculated due to extreme temps.
Groups were measured in MOA with calipers, (someday I'll get OnTarget for measuring results) with best at lowest velocity, and next best at max, although there was a big jump in elevation on the target at max load, much more than I'd expect with only a .5 grain increase.
Groups were: .316' at 20.5 gr., .665' at 21.5 gr., .557' at 22.5 gr., .563' at 23.0 gr., .234' at 23.5 gr.
All groups moved up the target with increased load, but the possibility exists that I skipped over a node around 22.0 grains. I'd loaded up 5 rounds in 22.0 grains to use as sighters, and after several scope adjustments, the last shot hit right on point of aim, so I may go back and explore that a bit.
The load at 22.5 gr. also fell right on POI, like the sighter at 22.0 gr., and shots 1 & 2 were at POI and spaced .577" (.288 moa) apart with shot #3 slightly higher, but barrel heating may have played into the results. Again, these were shot round robin.
So here's my question: Where to start refining the load? Do I go with the smallest group, the highest velocity ( second smallest group) or the two more consistent groups in the middle of the sequence?
I appreciate any and all help you guys can give. This 77 TMK looks to be a winner.