My wife has a .45 cal Rossi Youth ML.
I believe her owners manual RECCOMMENDS pyro pellets, but they aren't required. I will have to check that again.
Its hard to find much internet info/reviews on these guns (trust me I have tried), as it seems aren't many people using them.
My wife's rossi is a nice shooter and she took several deer with it this season. I was very impressed with that little gun and have only one complaint.
It is very light and it sure will kick the snot out of you, IF you put heavier loads in it. I started my wife off with a 245 grain bullet and 100 grains of pyro pellets. I couldn't believe how hard that gun kicked! She couldn't take it and I didn't blame her.
So I loaded it down to 80 grains of pellets and 175 grain bullet. That did the trick! She could shoot it all day long. I have since bought some 200 grain bullets to try out in it, as I didn't like the performance I was getting out of the 175 grain Powerboobs.
Its really been a great gun so far, but if your buying a youth model for a kid just make sure you keep those loads light.