Newby here, I just started reloading with my sons. We are loading for a H&R Handi Rifle in 357 Magnum. After three years of the kids practicing we have about 700 38 cases, so we decided to not let the go to waste. Because of the long barrel I picked up some 2400 and three different cast bullets. Two of the bullets are from Matt's the first is a RNHP in 148gr weight and the other a traditional SWCHP in 158gr. The other boolits are gun show SWC in 158gr. The 158's went 1370fps avg out of the 20" barrel and seem to show promise for grouping well. This was behind a 10.1grs of the 2400. The 148's were a completely different story, they avg 545fps behind the same 10.1gr load. The crazy thing is that there was less that 50fps std? What gives, is 148 to light for that slow powder, do I need to significantly increase the charge, or is there another explanation? The 158's had a similar standard deviation. I was very pleased overall on our first attempt at reloading. So give me your thoughts on a good long barrel powder to try behind the 148's. Here is a video of my daughter getting her first deer (16" eight point) with this rifle.