ABLRs can be extremely accurate but, you have to find where they like to be seated in your specific rifle. I shoot these in nearly every caliber and there doesn't appear to be a set "these like to be X off the lands" as some shoot great in close and others shoot best with a huge jump (.130" off lands in my 338 for example).
Try your H1000 and do a seat test with something around 61-62 grains. Start .10" off (or whatever longest mag length allows) and then back them off in .10" to .20" increments until your final test load is .100"-.130" off the lands. Whatever seating depth groups best, use that as your seating depth for whatever other powder you end up trying, should you need to try more.
So in short, do a seating depth test first and then work up your powder charge. Then you can do a final "fine tune" with seating after that if needed.