no real point here, just an imperfect example, shot today in the rain. obviously doing a ladder test at distance gets polluted as barrel harmonics and drop get mixed together, but i did it anyway, for no good reason.
I loaded 10 rounds very meticulously starting at 43.00g and going up by .10 exactly each round (except i'm an idiot and skipped 44.50g)
Then i shot them in order starting from 43.60 and going up, then going back to 43.00 and going up. I was having trouble seeing the cluster of holes on the cardboard so i couldn't tell exactly which order the last 5 rounds were shot in. I think I know, but I'm not 100% sure so I just put them all together with their velocities. Also, I did not change my hold at all, including no compensating for wind, so i believe the horizontal is mostly wind.
Couple interesting points...
IME, when you get close to the max, a LITTLE bit of powder will make a BIG difference in velocity. But back off a few grains and changes in powder don't produce nearly as large an increase in velocity. During matches, I'm usually shooting these more than 100 fps faster. This is a pretty moderate load so you can see it doesn't change that much. In fact, for the 5 rounds from 43.60-44.00g the velocity varied only 8 fps. and only 3 fps from 43.80 to 44.00. Of course, with a sample size of one... and I don't have an explanation for the next 5 shots which are all over, though my eye was getting a little fatigued so i let a couple of them sit in the chamber longer than a minute while i blinked and tried to focus.
another interesting note is despite varying the charge by a whole grain from 43.00 to 44.00, the 10-shot group was still sub-MOA and the vertical component is only 1.33" at 331 yards, which is well under .5 MOA
according to jbm, the min and max velocities 2832 fps and 2901 fps should give me drops of 13.9 and 12.9 respectively, so exactly 1" vertical at that distance, ignoring bullet exit/barrel harmonics.
shots 2 3 4 look pretty tight, 5 fps and only 2 bullet diameters of vertical. i'll make a few more of those and see if it is repeatable
I loaded 10 rounds very meticulously starting at 43.00g and going up by .10 exactly each round (except i'm an idiot and skipped 44.50g)
Then i shot them in order starting from 43.60 and going up, then going back to 43.00 and going up. I was having trouble seeing the cluster of holes on the cardboard so i couldn't tell exactly which order the last 5 rounds were shot in. I think I know, but I'm not 100% sure so I just put them all together with their velocities. Also, I did not change my hold at all, including no compensating for wind, so i believe the horizontal is mostly wind.
Couple interesting points...
IME, when you get close to the max, a LITTLE bit of powder will make a BIG difference in velocity. But back off a few grains and changes in powder don't produce nearly as large an increase in velocity. During matches, I'm usually shooting these more than 100 fps faster. This is a pretty moderate load so you can see it doesn't change that much. In fact, for the 5 rounds from 43.60-44.00g the velocity varied only 8 fps. and only 3 fps from 43.80 to 44.00. Of course, with a sample size of one... and I don't have an explanation for the next 5 shots which are all over, though my eye was getting a little fatigued so i let a couple of them sit in the chamber longer than a minute while i blinked and tried to focus.
another interesting note is despite varying the charge by a whole grain from 43.00 to 44.00, the 10-shot group was still sub-MOA and the vertical component is only 1.33" at 331 yards, which is well under .5 MOA
according to jbm, the min and max velocities 2832 fps and 2901 fps should give me drops of 13.9 and 12.9 respectively, so exactly 1" vertical at that distance, ignoring bullet exit/barrel harmonics.
shots 2 3 4 look pretty tight, 5 fps and only 2 bullet diameters of vertical. i'll make a few more of those and see if it is repeatable