I'm in the load development stage for a new 280 Ackley. It is a Cooper Excalibur, 1:10 twist. Looooong throat. Magazine length 3.400". I have some questions related to powders for this rifle but first here is what my load data consists of: Nosler custom 280 ackley brass(neck sizing) Fed210M primers Nosler 160gr Accubond bullets COL = 3.330” Powder H4831SC and RL22 I did barrel break in with some less expensive hornady interbond bullets and had some 1/2 MOA groups so I was excited to progress and improve from there. That seems like a long time ago and I'm not satisfied, well partially. I started loads way down at 55 grains and worked clear up to 63.5 grains with only a couple slightly sticky extractions. No primer cratering or flattening. I still am a tad nervous about that upper load being too hot even though I shot them between 75 – 82 degrees f. I started with the H4831SC because of the temperature resistance. I’ve read about the freeze tests etc and those test would mimic my range of environmental conditions. My elevation use also ranges from 1000ft to 8000ft. This is my do it all rifle, though I have several others, so I would prefer not to add powder as a cause for POI changes on top of the already extreme environmental conditions. So the H4831SC had fair results with a few groups in the .75”-1moa but when I switched to the RL22 those groups where cut in half and across a wide powder deviation. I shot a string of 3 round loads starting at 58.5 in ½ grain increments up to 61.5. of those 6 – 3 rnd groups one was .26”, one was .35”, one .46”, one .80 and the other two larger. I was extremely impressed with the rifle but not happy about the Hodgen powder not working out in this rifle. Maybe I’m getting to critical over these details but I’m planning to have dials made by leupold and I’d like them to be as close as possible for the loaded ammunition as possible. I still have not worked on bullet seating to fine tune the loads. My questions: Any advice on getting the H4831SC to work? Is it reasonable to expect to be able to get the H4831SC to perform to what I’ve already seen from the RL22? Would you recommend another temperature resistant powder like H450(is it even available?) or H1000, others? It’s damn near hunting season now so I’ll be loading the RL22 powder but will be back at it after the deer hunt and before the elk season which is at the end of October at 8000ft. Thanks in advance for the reloading wisdom.