Originally Posted by lloydsmale
personaly i think retumbo is to slow for the 7mag with any barrel lenght. Ive loaded the 7 rem mag for 20 years and have allways had my best luck with powders like hodgdon 4831, imr483 and 7828 and re19 and re22. Any slower then these powders and your not going to gain velocity your just going to use more powder.
What barrel length are you loading? According to my burn rate chart that lists 97 different rifle powders with number ,1 being fastest and 97 being slowest, R-22 is number 89, IMR 7828 is number 90, ad H-4831 is number 85. All the powders you listed are relatively slow burners.
Retumbo is slower at number 94 which is why I wondered if it could be used in a longer barrel.
With the powder shortages these days and the fact that I am the proud owner of like 24 pounds of Retumbo, I wanted to keep my options open.
This does not mean I am dead set on using this ( have 2 other rifles that eat it happily ), I run several powders for load development always but if a 26 inch barrel is necessary in an effort to have this powder as a good option, well it's worth it, however if I am spitting into a fan, then he extra 2 inches of barrel is not worth it.
I was always of the thought that a slow powder in a long barrel would produce better velocities, but that doesn't make me right.