RE: What a difference a prop makes!
The 12.25 X 3.75 prop is a 40 size control line prop but most are used on 40 size R/C 3D planes you see them on the 55's and also some people use them on the 50-56 size four strokes
One your rimfire you need to use the "E" series props. 11-4 or 12-4