First rifle for grandson. I found a prewar (WW2) Mossberg in .22 LR. They all had adjustable triggers. Bought another Mossberg barrel on Ebay and a .22 barrel reliner in .22 short from Brownell. Rifling for .22 short is 1-20, 1-16 for LR. .22 short makes less noise and doesn't seem to bother squirrels, but .22 LR makes them hide. .22 short will take squirrels at 50 yards with no problem. Had gunsmith mount good quality scope after relining bbl and installing it on rifle. Rifle can be changed back to LR just by easily changing bbls. One tapered screw does the job!