Let's start a new thread, so as not to go off-topic on Mr. Murdica's thread.
Max, the .300 RUM is basically the .404 Jeffrey case necked down to .30 and blown out a bit. I've never shot one. But back in the mid-1990s, Dave Tooley made up a bunch of chamberings on the .404 Jeffrey case. Left full length, and necked down to .30 caliber, it would be the same as your RUM. No one did that, for a .30, they always shortened it. Even in those days, the case shortened to 2.7 inches (MHV) was considered max for a .30. I shot the .30 SVH, same thing, but a 2.50 length case. Full-length was for .338s and larger.
Those who did use the MHV (2.7) used heavy bullets. Don't remember when the 240-grain Sierras came along, but that would be about right. And now, the newer Berger Hybrids -- the heavy ones.
I've also never regularly used powder slower than Rel-25. I have used 25 in an even smaller .30, an 8x68 necked down to .30. I could get 100% loading density with Rel-25 and 210 BIBs. Problem was, 4831 was more accurate, even though the loading density is far less.
I continue to use Rel-25 in a .338 on the full length .404 case, necked down, with the 300-grain Bergers. Going to make a smaller .338, so I can use 4831.
So, I can't be much help. H1000 has always teased -- always shot small but given mystery flyers. I don't know about the other extremely slow powders, Retumbo, VV N170, etc.
I do use 100 yards for all my testing. The only thing I do is if there is a bullet hole's worth of vertical, I make a mental note to see how the 1,000 yard groups perform. Usually, the groups do not have any more vertical than you would expect.
So, sort you bullets however you like, be careful with the charge weight, test jump versus jam, all the usual things. Try the heavier bullets first. Try different primers. I use the very mild "Wolf" (Russian) LR primers in my .30 SOB (close to a .308 Norma Magnum). But I've had barrels that preferred the Fed 215 with everything else the same. Go figure.
BYW, with mild primers, at the first sigh of a hangfire, stop. Wait a full minute before even thinking about opening the bolt. Clear the area behind you. Don't let your thumb get in the way. If the rifle fires as you open the bolt, it will fly back with tremendous force. Never happened to me, but I do know someone who lost a finger, piece of their thumb, and got a hole in their shoulder.
Good luck.
Max, the .300 RUM is basically the .404 Jeffrey case necked down to .30 and blown out a bit. I've never shot one. But back in the mid-1990s, Dave Tooley made up a bunch of chamberings on the .404 Jeffrey case. Left full length, and necked down to .30 caliber, it would be the same as your RUM. No one did that, for a .30, they always shortened it. Even in those days, the case shortened to 2.7 inches (MHV) was considered max for a .30. I shot the .30 SVH, same thing, but a 2.50 length case. Full-length was for .338s and larger.
Those who did use the MHV (2.7) used heavy bullets. Don't remember when the 240-grain Sierras came along, but that would be about right. And now, the newer Berger Hybrids -- the heavy ones.
I've also never regularly used powder slower than Rel-25. I have used 25 in an even smaller .30, an 8x68 necked down to .30. I could get 100% loading density with Rel-25 and 210 BIBs. Problem was, 4831 was more accurate, even though the loading density is far less.
I continue to use Rel-25 in a .338 on the full length .404 case, necked down, with the 300-grain Bergers. Going to make a smaller .338, so I can use 4831.
So, I can't be much help. H1000 has always teased -- always shot small but given mystery flyers. I don't know about the other extremely slow powders, Retumbo, VV N170, etc.
I do use 100 yards for all my testing. The only thing I do is if there is a bullet hole's worth of vertical, I make a mental note to see how the 1,000 yard groups perform. Usually, the groups do not have any more vertical than you would expect.
So, sort you bullets however you like, be careful with the charge weight, test jump versus jam, all the usual things. Try the heavier bullets first. Try different primers. I use the very mild "Wolf" (Russian) LR primers in my .30 SOB (close to a .308 Norma Magnum). But I've had barrels that preferred the Fed 215 with everything else the same. Go figure.
BYW, with mild primers, at the first sigh of a hangfire, stop. Wait a full minute before even thinking about opening the bolt. Clear the area behind you. Don't let your thumb get in the way. If the rifle fires as you open the bolt, it will fly back with tremendous force. Never happened to me, but I do know someone who lost a finger, piece of their thumb, and got a hole in their shoulder.
Good luck.