I have a 7mm Mashburn that was built on a Rem 700 action. Certainly not a lot of load data out there especially with new powders. Did a little looking around and I see the 28 Nosler case is listed as having a case capacity of 93.8 grs of H20. The 300 Win case is listed as having a capacity of 94 grs. now the shoulder is moved back a few thou on the 300 Win case to form the Mashburn case so capacity of the Mashburn may be reduced by a grain or two but still very close. It would make sense to reduce start loads by a grain or two to load the Mashburn but the 28 Nosler data will certainly provide Mashburn shooters some reference material. I am looking forward to trying StaBall HD in my rifle

I have both of those 2 cartridges and would advise you to look up data for the 7 Practical to use for the Mashburn. On average my loads for it are a good 6-10 grains less than I use in the 28 Nosler. It performs better with powders I’ve found too slow for the Mashburn. The Mashburn does very well with H1000, Retumbo and Ramshot Grand. Great cartridge overall, my favorite 7mm chambering.

John Thank You for your comments but I feel I have to comment back. I have checked several sites and they all list the 28 Nosler as holding 91-93 grs of H2O depending on the make of the brass.300 Win brass is listed as holding 91-94 grs of H2O again depending on brand. Several places list 7mm Mashburn as having approx 90 grs capacity in fireformed cases. The powders I wanted to try were mainly StaBall HD and Grand. Data for the Mashburn or the Practical was not availible anywhere I looked. In my first post I never suggested that I was going to use 28 Nosler data in my Mashburn. Since the Nosler holds 4-5 grs more water than the Mashburn case I used the Nosler start load minus 5 grs and worked up from there. I found StaBall HD to very good with 175 gr bullets in my Mashburn. I found similar results with Grand powder. If you are loading 10 grs MORE powder in your 28 Nosler than you do in your 7 Mashburn I'm thinking your Mashburn must be lightly loaded or you really have your Nosler stoked