Yesterday I did a ladder test at 300 yards using a different procedure than what I have seen on the internet, so far. Many of you are probably already doing your load testing this way but I haven't seen it so I thought I would share. This worked well for me so it might help out some one else. I also have a question about the results so stick around for that.
This load is for my R.E.P.R. 20" 1-11.25, with a USO 3-17. The loads are 41-45 grains of Varget under 175 grain SMKs inside of PMC brass lit by Remington 9 1/2 primers, loaded to 2.800 OAL +- a few thou measured off the meplats. I haven't figured out seating depth or distance to lands yet but they are fed through a mag. The firing sequence is round robing style. Everything was shot off a bipod prone with a rear bag. Wind was mute the first cycle, light the second cycle, and dead calm the last cycle which was getting towards dusk. All wind was from 9' to 6' when it was present. Also I don't have a crono so no FPS data is available.
I stapled up the targets like this on top of card board at 300 yards. The POA is the center of the upper target with un adjusted POI being the bottom target. Like this.
I worked up from 41 to 45 grains by increments of .5 grains. After each shot, using the scope and spotting scope, I would plot the impact on an identical target. This allowed me to stay in the firing position accept to pick up the brass, inspect it for pressure signs, and let the barrel stay cool. I saw no pressure signs up through 45. Here is the target which I would wright on while still prone behind the rifle.
After each “cycle” (what I am calling one shot of each different charge weight from 41-45 a total of 9 shots per cycle) I would walk down range and change out the target with the impacts for a fresh one. This prevented the holes from becoming too cluttered. I only had to walk out to the 300 yard line three times for this test. After all three cycles of the round robin were complete I was easily able to take my plotted target, compare it to the three targets with impacts, and mark the card board with the appropriate charge weight per hole. I can even tell on which cycle each hole was made per charge weight, but haven't as it doesn't seem necessary. Here is a picture of the holes on the card board color coded per charge weight. The POA stayed constant through out the entire round robin.
This picture shows the POA and amount of drop to each group.
As you can see the hotter my loads got the POI actually dropped. If I were to continued upward with the charge weight I assume the POI would start to rise. I am sure this is not un common and any information or links to exhaustive articles any one has about this I would appreciate it.
As for which charge weights to focus on and refine you can see that 41 grains (silver) grouped the best vertical dispersion at .3” with a width of 2.73” however no nearby charge weights grouped very good. Looking at 44, 44.5, and 45 grains I can see that 44 (black) had the best vertical dispersion of .66” and the best width of 2.55” while 33.5 (puke yellow) was terrible. You can see that 44.5 and 45 grouped quite close to 44 however vertical dispersion for 44.5 (light blue) was 1.4” and the vertical for 45 (pink) was .96”. I realize the width is not important at this point however I included it for the sake of more information. Vertical dispersion between just 44 & 45 is .87” while the vertical between 44 & 44.5 is 1.69 and it is the same between 45 and 44.5. I think I will start at 44 and work upwards to 45.6 by increments of .2. I saw now pressure signs to 45 so as I go above 45 I will look for them. Should I put together some charges below 41 and see how they group? This load will be for long range steel so I would prefer the higher velocities of the 44+ loadings however the lower POI confuses me and I don't have a crono.
I appreciate any insights you all may have so thank you for your input.
This load is for my R.E.P.R. 20" 1-11.25, with a USO 3-17. The loads are 41-45 grains of Varget under 175 grain SMKs inside of PMC brass lit by Remington 9 1/2 primers, loaded to 2.800 OAL +- a few thou measured off the meplats. I haven't figured out seating depth or distance to lands yet but they are fed through a mag. The firing sequence is round robing style. Everything was shot off a bipod prone with a rear bag. Wind was mute the first cycle, light the second cycle, and dead calm the last cycle which was getting towards dusk. All wind was from 9' to 6' when it was present. Also I don't have a crono so no FPS data is available.
I stapled up the targets like this on top of card board at 300 yards. The POA is the center of the upper target with un adjusted POI being the bottom target. Like this.
I worked up from 41 to 45 grains by increments of .5 grains. After each shot, using the scope and spotting scope, I would plot the impact on an identical target. This allowed me to stay in the firing position accept to pick up the brass, inspect it for pressure signs, and let the barrel stay cool. I saw no pressure signs up through 45. Here is the target which I would wright on while still prone behind the rifle.
After each “cycle” (what I am calling one shot of each different charge weight from 41-45 a total of 9 shots per cycle) I would walk down range and change out the target with the impacts for a fresh one. This prevented the holes from becoming too cluttered. I only had to walk out to the 300 yard line three times for this test. After all three cycles of the round robin were complete I was easily able to take my plotted target, compare it to the three targets with impacts, and mark the card board with the appropriate charge weight per hole. I can even tell on which cycle each hole was made per charge weight, but haven't as it doesn't seem necessary. Here is a picture of the holes on the card board color coded per charge weight. The POA stayed constant through out the entire round robin.
This picture shows the POA and amount of drop to each group.
As you can see the hotter my loads got the POI actually dropped. If I were to continued upward with the charge weight I assume the POI would start to rise. I am sure this is not un common and any information or links to exhaustive articles any one has about this I would appreciate it.
As for which charge weights to focus on and refine you can see that 41 grains (silver) grouped the best vertical dispersion at .3” with a width of 2.73” however no nearby charge weights grouped very good. Looking at 44, 44.5, and 45 grains I can see that 44 (black) had the best vertical dispersion of .66” and the best width of 2.55” while 33.5 (puke yellow) was terrible. You can see that 44.5 and 45 grouped quite close to 44 however vertical dispersion for 44.5 (light blue) was 1.4” and the vertical for 45 (pink) was .96”. I realize the width is not important at this point however I included it for the sake of more information. Vertical dispersion between just 44 & 45 is .87” while the vertical between 44 & 44.5 is 1.69 and it is the same between 45 and 44.5. I think I will start at 44 and work upwards to 45.6 by increments of .2. I saw now pressure signs to 45 so as I go above 45 I will look for them. Should I put together some charges below 41 and see how they group? This load will be for long range steel so I would prefer the higher velocities of the 44+ loadings however the lower POI confuses me and I don't have a crono.
I appreciate any insights you all may have so thank you for your input.
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