I know when someone asks what powder to use, they are trying to cut down the development time and expense. There are a variety of powders that work well in the 204 Ruger. BL C2 is one of them, it is similar to the burn rate of W748. Mitchel, I believe, has had excellent results using BL C2 as well as Tim. Just because they are similar in burn rate does not make them react the same for your particular application. I had a 222 Remington that loved a mid load of BL C2, but did not shoot worth a plug nickle with W 748. W748 may work better for you, you just do not know until you try it. I also know that some folks have had excellent results using Benchmark as well as TAC and Varget. Being the mouth of a 204 is so small on a 204 a finer powder works well for getting into the case. Being BL C2 is a ball powder, it is certainly among those that will pour easily. That is the exact reason I tried it in my 222, it metered well out of my powder thrower. For some reason, Hornady (7th edition) does not list BL C2 for their 204 loads. Sierra, Nosler and Speer do not list any 204 loads because they do not make 204 bullets or the 204 is too new to make it in their latest editions. I do not have the latest Lyman manual, but have the 48th edition and it does not list any loads with the 204. Since it a Hodgdon powder, Hodgdon does list some loads for it in their manual. I would think it would be a good place to start. You can get on line to find loads using BL C2 powder. If Bl C2 does not work out for you then try one of the other powders I suggested. There are lots of powders that are suitable for the 204. Just about any of the medium burning powders can work. Good Luck and Good Shooting
BTW load development can be fun, but it can be expensive and then again; it can be frustrating too - but highly rewarding when you hit on the magic formula
Start low and work your way up carefully - no matter which powder you are using
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