H4350 lot to lot or temperature inconsistency?

[32Special]

I have a new .260, and I worked up loads using H4350. Powder is hard to come by, and I had two unopened jars of H4350 that was packaged shortly before they started marking the powder as "extreme." I've never seen any data suggesting the "extreme" powder loads were different than the older H4350. I used that powder for load development thinking that the mild spring temperatures would be a good time to use it, and saved my limited "extreme" H4350.

I finally had a load: virgin Lapua, 210M, 142 SMK, mild charge of H4350 that averaged 2739 at 55-60F from a 26" barrel. OAL set at 2.800. I ran out of the older powder, and made loads with the same lot virgin brass, primers, bullets but using the newer "extreme" powder. I only made 15 to test, and shot them yesterday when the temperature was 80-85 F.

Velocity was up 70-80 fps on average. Shot to shot variation was good. Admittedly, it was 25 degrees warmer, but 80 fps increase? I didn't expect that magnitude of change. I still don't have any real excess pressure signs, but it is a little higher than I want.

Questions:

1) Is this typical of H4350? I've never encountered that much lot to lot variation in other powders.

2) Based on my earlier experience, I would have to drop the powder charge by about 1 grain to get back down to my earlier velocity where I had a good "sweet spot." Would matching my earlier velocity with the new lot of powder preserve that sweet spot?

I don't like the idea of having to work up new loads for every new lot of powder. Previously, I'd buy powder a keg or two at a time, but now, like everyone else, I'm forced to take whatever I can get which has been 1# cans.

Suggestions and experience appreciated. Thanks.

 

[Aimsmall55]

I've just started on my second lot and I'm getting the exact same velocity in my creedmor. What's the lot #

 

[32Special]

Well, I threw away the cans of the old stuff which were both the same lot, and sealed when I opened them. The stuff I'm using now is the bottom of an old 8# keg of H4350 extreme (lot 8 06210113796) that I blended with a couple of new cans of extreme (lot 10320135158). I was hoarding the extreme with the idea that I could load several hundred non-temperature sensitive rounds.

I'm afraid that I'll just have to load 10 at the old charge and 10 rounds 1.3 grains lower and make a point to shoot them at 55-60 degrees. Assuming 7 fps per .1 grain (based on prior tests with the old powder), that should take me to the old velocity ASSUMING the powder is simply hotter. Shooting them both at the 55-60F temperature will settle the temperature part of the question. I just checked my notes, and my actual average velocity was up 89 fps over what I was getting with the older powder.

Problem is I have a match coming up, and I need to get this ammo question solved.

I've read that with lot to lot vairations, the trick was to load to match your old velocity and that would keep your node/sweet spot. Can anyone confirm that to be true?

Thanks.

 

[Aimsmall55]

Well, I threw away the cans of the old stuff which were both the same lot, and sealed when I opened them. The stuff I'm using now is the bottom of an old 8# keg of H4350 extreme (lot 8 06210113796) that I blended with a couple of new cans of extreme (lot 10320135158). I was hoarding the extreme with the idea that I could load several hundred non-temperature sensitive rounds.

I'm afraid that I'll just have to load 10 at the old charge and 10 rounds 1.3 grains lower and make a point to shoot them at 55-60 degrees. Assuming 7 fps per .1 grain (based on prior tests with the old powder), that should take me to the old velocity ASSUMING the powder is simply hotter. Shooting them both at the 55-60F temperature will settle the temperature part of the question. I just checked my notes, and my actual average velocity was up 89 fps over what I was getting with the older powder.

Problem is I have a match coming up, and I need to get this ammo question solved.

I've read that with lot to lot vairations, the trick was to load to match your old velocity and that would keep your node/sweet spot. Can anyone confirm that to be true?

Thanks.

Yes and no ( in my experience ) .... Question of pressure. If your sweet spot is 1.27 grains lower and your running a low charge (especially in colder weather) it could be dangerous. My suggestion would be roll with what you got and let the past lot be exactly that .. The past. That's only if this load is shooting to your standards. I'm assuming your f-class where anything above 1/4 moa at 100 is intolerable. That being said if its still shooting lights out .... What the hell. 89 fps will only help you in bucking the wind. Ismh that if your Es and sd is up from your lower charge and your using fgm210m primers , try the br2's. they will give you a speed roughly slower and your Es and sd will almost certainly be lower. Just my opinion.