Yes I use mag primers for Lil'Gun.
Loads are usually the same/similar for rifle vs pistol rounds. The exceptions happen when you get into things that just *aren't* fun to shoot in handguns like full house 45-70 loads. The only difference becomes speed due to longer burn time. I believe H-110 will generate slightly more fps vs Lil'Gun in rifle length barrels if handgun FPS being equal.
Lil'Gun indeed generates less pressure with fairly impressive performance. Don't hunt with it but like it otherwise, especially with fast lead bullets.