any gun you can hit something with will take a tree rat(squirell)some days i take the 22 and give myself a challenge others its the 12 ga pump or semi and a modified with 2 3/4 6 or 7 1/2....or some days i will bust out the ole single shot 20 ga shooting 3 inch mags with copperplated 6's....squirell master i agree...me and my dad hunt within 100yds of eachother moving after ever 30-45 mins moving about 50yds or so...and when one of us shot it usually makes another squirell give itself away! i wounded one once and when my dad shot he cam crawling down the tree so i had to run away from the treee and shot it! i duno how he was in the same tree i was leaning on but it was him....full of copper 6's...within a 500yd range moving as we do we always get about 6-10 together...i dont think shots effect them much...they recieve no pressure at all except us at one spot we hunt(the one i described how we move) and thats the one we hunt alot because its close to home...maybe if htey recieve heavy pressure it might effect them but rat hunting isnt all too big for the most part...