200 AB, Retumbo, 300 rum

[Stavi300RUM]

What are you using for development? Nosler #7 manual shows starting at 88 and 91.5 gr as MAX, but I see a lot of people are using 92 gr as a starting point and going up to 95gr. Any suggestions without blowing up my gun?

 

[mrultramag]

I've shot retumbo w/200AB in 300 Rum. I think I went as high as 95 gr looking for tight groups. For my gun-Rem 700 (26in bbl)- RL25 92 gr is more accurate and gives me 3150 fps. That is about what you should expect velocity from retumbo as well. Many people get 3200 with retumbo and the 200 AB but may be leaning on it a little. This is using a 26" bbl and Remington cases. Nosler data for 200 gr is using nosler cases and 24" bbl. Shorter bbl= less velocity. Different case=different capacity. work up your load. use a chronograph and watch for excessive pressure signs.

 

[Screwey1]

Found best groups in my rifle with 92 gr. Tried to go a little higher and accuracy suffered. I started at 91 and went up .5 gr. each time, shot at target through chrony at the same time for both speed and accuracy. If you need to push speed, start low, shooting once fired brass that was neck sized, and watch for pressure signs on base. In my experience, new brass won't show pressure as soon as a neck sized once fired.
I think it is because more gas escapes past the new casing.
I showed no pressure signs at 92 gr. but all rifles are not created equal.

 

[cohunter14]

As has been said, start around 90 or 91 grains and work up. I ended up at 93 and 3,100 fps with a 26" barrel. No pressure signs up to 94 for me.

 

[Stavi300RUM]

Thank you for the great information. I was just puzzled how the newest Nosler manual shows a max of 91.5 but Hodgdon shows a max of 95.5. I loaded up to 93, but will settle at 92.5 because those grouped the best out to 300 yards.
Thanks everyone!