[Standard Disclaimer: The below info was of interest in my gun, yours will be different so start at minimum book load and be careful and watchful working up.]
Lots of detailed info below, but there is the summary:
I started playing with Hodgon's H100V in my .260AI. Found a very accurate load at good velocity. The best group was found at 44.7 grains H100V at 2911 fps velocity with a SMK 142 gr bullet. The remaining big unanswered question is: What will be the temperature sensitivity?
Details:
Gun: .260 Remington AI, New 24 inch Krieger barrel, 1:8 twist. All testing done with Lapua 260 Rem. cases pre-fire-formed and resized, necks trimmed to length and shaved to consistent thickness, set to maximum AICS mag length (this is why I didn't try to further improve the load later by trying OAL variations). All testiing with Sierra MatchKing 142 gr bullets coated with Boron Nitride (BN).
I decided I should develop a proper load with this new barrel rather than just winging it with ballpark loads suggested on the Internet. So I prepared for the following regimen (carefully recording atmospheric data each time):
1. Rough ladder test from 41.0 to 46.0 grains of H100V to find node(s) with minimal elevation change.
2. Once node found, play with 0.3 gr. powder changes and look for best group.
3. Chronograph best load found and plot data
4. Perform scope alignment per Brian Litz instructions
5. Zero at 100
4. Test ballistic software predictions (come-ups) at 300 and 600 yards.
1: I ran a ladder test from 41.0 to 46.0 grains of H100V, in 0.5 gr increments. Best elevation groups were at 42 grains and 45 grains. I also chrono'ed these loads (separately) with a MagnetoSpeed. Velocities ranged from 2660 fps average at 42.0 grains and 2960 fps average at 46.0 grains -- but I only shot one round of the 46.0 load because bolt extraction got tight. The 45.5 load showed some ejector "shininess" on the case so I think that load also too hot. 45.0 gr and below showed no pressure signs.
2: I next zeroed in on the 42.0 to 45.0 range and loaded 5 cartridges at each of 0.3 load increments. (so, 42.0, 42.3, 42.6 etc up to 45.0 grains). I shot these for group size on a perfect windless (per Kestral) day @ 41.0 F at 80.5% humidity. Kestral gave Density Altitude this day at -675. The best group was found at 44.7 grains H100V (100 yards). Group size was 0.27 inches mostly horizontal dispersion. I also then moved the target back to 200 yards and shot the same 44.7 load and got 0.6 inch dispersion. I am happy with this load!
3: I chrono'ed this load (Magnetospeed again) at an average of 2911 fps from a warm but not hot barrel, ES was 17 fps.
4: I set up a vertical scope alignment target per Brian Litz's instructions on his DVD and found my NF 5.5x22 scope was already aligned perfectly and had very repeatable clicks (but I already knew that, just mentioning it here because it is a very useful step if you haven'/t done it.) DO THIS if you haven't, no matter how much your scope cost.
5: I zero'd at 100 yards (again a nice tight <0.5 MOA group) and entered my atmospheric and load data into Shooter and ran the numbers.
6: The Shooter data was within one click (0.25 MOA) at the longer ranges I tested.
Comments: H100V is an interesting powder, called a "hybrid" by Hodgdon. It meters very easily (all the load testing above was individually-weighed charges on a high-quality electronic scale, which I believe to be accurate to within 0.5 grain.) Pressures seemed to ramp up fast though with even the 0.3 grain increases. From the data above you can see that from 42.0 to 45.0 grains showed absolutely no pressure signs, then 45.5 grains showed slightly flattened primers and ejector marks, then 46.0 grains was definitely hot with significant bolt stickiness, flat primers, and very noticeable ejector marks. So, be VERY CAREFUL as you walk up the ladder.
This rapid pressure rise also makes me wonder about temperature sensitivity on hotter days. I'll be watching this. H100V is NOT on of Hodgdon's Extreme line of powders. I still think for most folks Hodgdon H4350 is best for .260AI, and especially for standard .260 Remington cartridges. But if your rifle doesn't quite seem to like H4350, then H100V might be worth a trial. (And yes, I have also tried H4895-SC and found good accuracy but velocities no better than about 2800 in an accurate load.)
The BN coating I use is for additional barrel life and cleaning ease, not to try and gain velocity. I believe coating the bullets with BN gives my about 25% more barrel life with a given load.
I hope this information is interesting to someone.
Lots of detailed info below, but there is the summary:
I started playing with Hodgon's H100V in my .260AI. Found a very accurate load at good velocity. The best group was found at 44.7 grains H100V at 2911 fps velocity with a SMK 142 gr bullet. The remaining big unanswered question is: What will be the temperature sensitivity?
Details:
Gun: .260 Remington AI, New 24 inch Krieger barrel, 1:8 twist. All testing done with Lapua 260 Rem. cases pre-fire-formed and resized, necks trimmed to length and shaved to consistent thickness, set to maximum AICS mag length (this is why I didn't try to further improve the load later by trying OAL variations). All testiing with Sierra MatchKing 142 gr bullets coated with Boron Nitride (BN).
I decided I should develop a proper load with this new barrel rather than just winging it with ballpark loads suggested on the Internet. So I prepared for the following regimen (carefully recording atmospheric data each time):
1. Rough ladder test from 41.0 to 46.0 grains of H100V to find node(s) with minimal elevation change.
2. Once node found, play with 0.3 gr. powder changes and look for best group.
3. Chronograph best load found and plot data
4. Perform scope alignment per Brian Litz instructions
5. Zero at 100
4. Test ballistic software predictions (come-ups) at 300 and 600 yards.
1: I ran a ladder test from 41.0 to 46.0 grains of H100V, in 0.5 gr increments. Best elevation groups were at 42 grains and 45 grains. I also chrono'ed these loads (separately) with a MagnetoSpeed. Velocities ranged from 2660 fps average at 42.0 grains and 2960 fps average at 46.0 grains -- but I only shot one round of the 46.0 load because bolt extraction got tight. The 45.5 load showed some ejector "shininess" on the case so I think that load also too hot. 45.0 gr and below showed no pressure signs.
2: I next zeroed in on the 42.0 to 45.0 range and loaded 5 cartridges at each of 0.3 load increments. (so, 42.0, 42.3, 42.6 etc up to 45.0 grains). I shot these for group size on a perfect windless (per Kestral) day @ 41.0 F at 80.5% humidity. Kestral gave Density Altitude this day at -675. The best group was found at 44.7 grains H100V (100 yards). Group size was 0.27 inches mostly horizontal dispersion. I also then moved the target back to 200 yards and shot the same 44.7 load and got 0.6 inch dispersion. I am happy with this load!
3: I chrono'ed this load (Magnetospeed again) at an average of 2911 fps from a warm but not hot barrel, ES was 17 fps.
4: I set up a vertical scope alignment target per Brian Litz's instructions on his DVD and found my NF 5.5x22 scope was already aligned perfectly and had very repeatable clicks (but I already knew that, just mentioning it here because it is a very useful step if you haven'/t done it.) DO THIS if you haven't, no matter how much your scope cost.
5: I zero'd at 100 yards (again a nice tight <0.5 MOA group) and entered my atmospheric and load data into Shooter and ran the numbers.
6: The Shooter data was within one click (0.25 MOA) at the longer ranges I tested.
Comments: H100V is an interesting powder, called a "hybrid" by Hodgdon. It meters very easily (all the load testing above was individually-weighed charges on a high-quality electronic scale, which I believe to be accurate to within 0.5 grain.) Pressures seemed to ramp up fast though with even the 0.3 grain increases. From the data above you can see that from 42.0 to 45.0 grains showed absolutely no pressure signs, then 45.5 grains showed slightly flattened primers and ejector marks, then 46.0 grains was definitely hot with significant bolt stickiness, flat primers, and very noticeable ejector marks. So, be VERY CAREFUL as you walk up the ladder.
This rapid pressure rise also makes me wonder about temperature sensitivity on hotter days. I'll be watching this. H100V is NOT on of Hodgdon's Extreme line of powders. I still think for most folks Hodgdon H4350 is best for .260AI, and especially for standard .260 Remington cartridges. But if your rifle doesn't quite seem to like H4350, then H100V might be worth a trial. (And yes, I have also tried H4895-SC and found good accuracy but velocities no better than about 2800 in an accurate load.)
The BN coating I use is for additional barrel life and cleaning ease, not to try and gain velocity. I believe coating the bullets with BN gives my about 25% more barrel life with a given load.
I hope this information is interesting to someone.
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