I tried H1000 in my 22in with 77tmk. I couldn't get enough in there to get it to outperform H4350. Rl16 along with full cases of N555 rl23 didn't he best, 3300+ fps. H1000 was 100-150fps behind these. Lapua brass, less capacity than HDY. H4350 moved 77s at 3275 at pressure, H1000 was around 3200 with a 12" drop tube and full case. Just my personal findings.
Edit*
Just looked at HDY data, they have a max for H4350 at 37.7 with 80, I went up to 42gr with Alpha brass in the new 18in barrel shooting 88s. Their max of N555 is 39.6gr at 3150 from a 24in, I'm shooting 43gr with 88s comfortably at 3100 from a 6in shorter barrel. Take the lawyer data with a grain of salt.