Does anyone have any experience with H-1000 powder? currently using H4831, someone suggested H-1000 to me, would be used in a .300 Win Mag. Never used any other powder, pretty new at reloading...Thanks in advance!

I have used H4831 for over 17 years for my 300 WM and now use H4831sc. I was told the same thing about H1000 and tried a pound. I didn't get the results I was used to w/ H4831 so I went back. Your mileage may vary.

I'd be using IMR 7828.

For years us handloaders had trouble duplicating the factory velocity of the 7Rem Mag. IMR releasted the "New" 7828 and our velocities were what they were advertised.
I would try 7828 as I too believe that H-1000 is too slow.