I might shoot it again starting from shots 5-12 or 13.....but I think there is something there right around shot 8, the book max. I never felt pressure on bolt lift so I may make a 13 or 14 in .3
And pretty sure I will do a ladder with h-1000.
Looks like this rifle may be a shooter, but I don't even have 100 down the tube...
Don't mind me, I just like to stir the pot a little
But... I sometimes wonder if a random grouping like you got for 7 8 9 is just coincidence? One way to find out is to shoot it again starting at maybe 6. If 7 8 and 9 group again, I would say you probably have something.
My load development technique is to find the working max in my rifle based on pressure signs and start grouping there. If accuracy is acceptable, that's what I use. I might play with seating depth before trying a lighter load.
That said, those are light loads in the 300 RUM. I shot the 210 VLD's with 93 gr of Retumbo as a max load. Are you chrony'ing these loads? I'm guessing you are getting less than 2800 fps with 87 gr of Retumbo.
Also, I like to have at LEAST 90% case capacity for my go to loads, especially hunting loads. 100 gr of Retumbo is about 100% of usable case capacity in the 300 RUM depending on how deep you seat your bullet. 87 gr is going to be about 87%. Take a sized case and dump 100 gr in it and see how much it fills it. It should come up just under the shoulder neck junction. H1000 is faster than Retumbo and you will get less filled capacity. Those powders are best with lighter bullets.
I've been working up a load with RL33 and the 230 Hybrids. My working max (by pressure signs in my rifle) is 102 gr. With 103 gr I got a very light stiff bolt. 102 of 33 is about 98-99% capacity with a COAL of 3.92 33 is denser than Retumbo. A few guys have been having very good results with 33 and the 230's. Best results are with the bullets close to the lands, maybe .010
I have found a lot of published data for the 300 RUM to be on the conservative side, especially Berger data. Take that for what it's worth.