I did my AR15 pistol with Krylon. Its composite material just like the 15-22.
I did the whole weapon in Tan. Then did big "strips" in OD Green, starting in front and working back. Then take a Natural Sea Sponge, found at a local hobby store, and add the "digital" look. You will spray Desert tan on to a paper plate, dab the sponge in the paint and then
tab the sponge on the OD Green. Get another small piece of sponge, dab it in the OD Green
and then Dab the Tan. So basically the dabbed paint is on the opposite color. Once done, take gray and black, and dab it all over the rifle.
Viola... your done and this is what it looks like
Did my daughters .22 the same way, using a little different color scheme
Couple of things, Cut the sponge into small pieces, doesnt take a big piece to get the look right.
And if you screw up and don't like how something looks, spray over it, and start again.
Finish it all off with a matte clear coat