goodgrouper
tryingtobeabettergrouper
Where I live in Utah, I am blessed (cursed) to have some of the largest temperature swings imaginable this time of the year due to our very low humidity here. It's generally not much above 30%. I say cursed because the amount of clothing you have to take around everywhere is a pain but mainly because it's hard to tune guns in when the temp can swing 50+ degrees like it did today. It's a blessing in that it makes for some really good experiment opportunities.
In the canyon close to my home, there is a spot where I shoot where the sun won't reach me until 10:00 in the morning and the overnight cold air settles in for a brisk start to the day. Upon arrival this morning at 6:00 a.m., the humidity was 33% and temperature was 34 degrees! There was frost on the grass and my breath would hang in the air long enough to obscure my view through my headlamp light.
I began to set up the windflags, targets, reloading gear, and my Oehler 35 chronograph. The wind was about 3 mph and swirling around.
I began the experiment shooting several loads of N133 and recording the speeds, the deviations, and the group sizes at about 7:00 a.m. The temp at this time actually dropped to 33 degrees. I began with 53 clicks and ran it all the way up to 55 clicks. I found two distinct windows where the groups were best and the deviations (coincidentally?) were also smallest. One at the bottom end and one at the top end. I also noted that the load .3 grain above and .3 grain below the optimum shot pretty decent and also had small deviations. When the loads were shot outside the node windows, the numbers got bad both in group size and deviations.
Then I switched the powder in the hopper to H322 and did the same thing only with less clicks due to the faster burn rate of H322. I ran a ladder from 50 clicks to 52 clicks. I noted that it too had two nodes, one high and one low. However, the best accuracy in the upper node had only the second best deviations. The lowest deviation load shot a group .030" bigger but both were under 15 fps. I also noted that the node window was much narrower with H322. The low end node would not shoot near as good of groups or deviations .3 grain above or below the "sweet spot". I feel I had a pretty good handle on the situation as far as groups were concerned as the wind was still easy to cope with at a little breeze of 2-3 mph.
Anyhow, the best load for both powders as far as group size and numbers was in the upper node and it yielded a nice .180" for the H322 and .195" for N133. Interestingly enough, the velos for these groups in the freezing weather was 3401 and 3413 respectively. So it seemed that no matter the powder used, this particular barrel shot the best around this velocity give or take 12 fps at this temperature.
After a warmup and a nap in the truck, I set up some new targets and moved my reloading bench into the shade. It was now quarter to 10:00 and the thermometer said it was 65 degrees. I prepped some cases, and b.s'ed a bit with some other shooters that had shown up and by 11:30 the temp was at 75 degrees and climbing quick. So I threw the N133 back in the hopper and re-ran the same ladder doing nothing different and recorded the velos.
By the end of the N133 ladder, the temp gauge said it was 83 degrees--a swing of 50 degrees!! The wind or breeze actually had died completely off by this time but a touch of mirage had set in.
Looking at the velocities, the N133 had gone up very in speed very uniformly and equated to about 1 foot per second for every 1 degree increase. The best load was now shooting at 3451 and the group actually shrank to a .177".
Then it was time for H322.
The temp was holding steady at 84 degrees and the conditions were beautiful. I ran the same ladder and was surprised to see that H322 also increased it's velocities very uniformly and about 1 foot per second per degree. The velocity deviations on the load also remained at about the same levels going from 11 to 16. But again, the sweet spot was narrow with this powder and a click above or below dramatically increased the group size and the deviations. But the sweet spot again yeilded a slightly smaller group than N133 which measured .152"
CONCLUSION:
N133 and H322 velocities increase very similarly to one another at about 1 foot per second per degree. However, the N133 provided slightly better deviations and gave better accuracy above and below the "sweet spot". H322 would shoot slightly smaller groups when the sweet spot was reached, but it was much easier to get bumped out of tune. In other words, it was less forgiving.
Both powders increased about .30 fps per .3 grain increase of powder and showed very similar pressure curves although H322 was decidedly faster in burn rate because same velos were attained with several grains less powder.
Now for the second experiment: Volume in temp swings.
While my powder thrower was in the shade for loading the ammo used in the first half of the day, I decided to load a few round of N133 with the bare hopper in the sun, then with the hopper in the sun with a white sock over it.
I compared the velos to the velos attained in 83 degree weather with the hopper in the shade. The gun was to remain in the shade to keep the comparison fair.
The results were the velo DROPPED about 40 fps when the powder was thrown from the bare hopper in the sun and they DROPPED 10 fps when the white sock was on the hopper. I can only assume that the reason for the drop was the sun heated up the kernels of powder and the thrower threw less powder by weight because of the increase of volume. Very interesting. Unfortunately, I did not have my scale with me to see what the difference in weight was from shade to sun but I will have something else to test next time at the range!
FWIW!
In the canyon close to my home, there is a spot where I shoot where the sun won't reach me until 10:00 in the morning and the overnight cold air settles in for a brisk start to the day. Upon arrival this morning at 6:00 a.m., the humidity was 33% and temperature was 34 degrees! There was frost on the grass and my breath would hang in the air long enough to obscure my view through my headlamp light.
I began to set up the windflags, targets, reloading gear, and my Oehler 35 chronograph. The wind was about 3 mph and swirling around.
I began the experiment shooting several loads of N133 and recording the speeds, the deviations, and the group sizes at about 7:00 a.m. The temp at this time actually dropped to 33 degrees. I began with 53 clicks and ran it all the way up to 55 clicks. I found two distinct windows where the groups were best and the deviations (coincidentally?) were also smallest. One at the bottom end and one at the top end. I also noted that the load .3 grain above and .3 grain below the optimum shot pretty decent and also had small deviations. When the loads were shot outside the node windows, the numbers got bad both in group size and deviations.
Then I switched the powder in the hopper to H322 and did the same thing only with less clicks due to the faster burn rate of H322. I ran a ladder from 50 clicks to 52 clicks. I noted that it too had two nodes, one high and one low. However, the best accuracy in the upper node had only the second best deviations. The lowest deviation load shot a group .030" bigger but both were under 15 fps. I also noted that the node window was much narrower with H322. The low end node would not shoot near as good of groups or deviations .3 grain above or below the "sweet spot". I feel I had a pretty good handle on the situation as far as groups were concerned as the wind was still easy to cope with at a little breeze of 2-3 mph.
Anyhow, the best load for both powders as far as group size and numbers was in the upper node and it yielded a nice .180" for the H322 and .195" for N133. Interestingly enough, the velos for these groups in the freezing weather was 3401 and 3413 respectively. So it seemed that no matter the powder used, this particular barrel shot the best around this velocity give or take 12 fps at this temperature.
After a warmup and a nap in the truck, I set up some new targets and moved my reloading bench into the shade. It was now quarter to 10:00 and the thermometer said it was 65 degrees. I prepped some cases, and b.s'ed a bit with some other shooters that had shown up and by 11:30 the temp was at 75 degrees and climbing quick. So I threw the N133 back in the hopper and re-ran the same ladder doing nothing different and recorded the velos.
By the end of the N133 ladder, the temp gauge said it was 83 degrees--a swing of 50 degrees!! The wind or breeze actually had died completely off by this time but a touch of mirage had set in.
Looking at the velocities, the N133 had gone up very in speed very uniformly and equated to about 1 foot per second for every 1 degree increase. The best load was now shooting at 3451 and the group actually shrank to a .177".
Then it was time for H322.
The temp was holding steady at 84 degrees and the conditions were beautiful. I ran the same ladder and was surprised to see that H322 also increased it's velocities very uniformly and about 1 foot per second per degree. The velocity deviations on the load also remained at about the same levels going from 11 to 16. But again, the sweet spot was narrow with this powder and a click above or below dramatically increased the group size and the deviations. But the sweet spot again yeilded a slightly smaller group than N133 which measured .152"
CONCLUSION:
N133 and H322 velocities increase very similarly to one another at about 1 foot per second per degree. However, the N133 provided slightly better deviations and gave better accuracy above and below the "sweet spot". H322 would shoot slightly smaller groups when the sweet spot was reached, but it was much easier to get bumped out of tune. In other words, it was less forgiving.
Both powders increased about .30 fps per .3 grain increase of powder and showed very similar pressure curves although H322 was decidedly faster in burn rate because same velos were attained with several grains less powder.
Now for the second experiment: Volume in temp swings.
While my powder thrower was in the shade for loading the ammo used in the first half of the day, I decided to load a few round of N133 with the bare hopper in the sun, then with the hopper in the sun with a white sock over it.
I compared the velos to the velos attained in 83 degree weather with the hopper in the shade. The gun was to remain in the shade to keep the comparison fair.
The results were the velo DROPPED about 40 fps when the powder was thrown from the bare hopper in the sun and they DROPPED 10 fps when the white sock was on the hopper. I can only assume that the reason for the drop was the sun heated up the kernels of powder and the thrower threw less powder by weight because of the increase of volume. Very interesting. Unfortunately, I did not have my scale with me to see what the difference in weight was from shade to sun but I will have something else to test next time at the range!
FWIW!