I ordered a 7mm-6.5 PRC reamer from Manson. Mine will have a 0.045" freebore to accommodate 180s in a SA, but you could go longer in a XM or LA and run 190s. I wanted to do a 7mm SAUM but I've been looking for months and can't find brass. Seriously I love the 7SAUM round, but I'm not going to have a gun that has to sit in the rack be cause I can't get brass. The 6.5 PRC brass is available from Peterson, Lapua, etc so it's quality stuff and a little more prevalent. I can get it on gun broker right now, it's just $3/case. But can you get 7SAUM on there at any price? No. At this point, the only brass prep operation that is required for the conversion as far as I know is a pass over a 7mm sizing mandrel so no big deal. I'm thinking of it as a grownup 7mm-08 and I think it would fill your gap nicely, plus all the powders you're using for the 25PRC may transfer over depending on weights and barrel lengths and stuff.