i had a 2.5x on a 22/45 ruger mkII also. it worked well. i would only use one on a rimfire, unless i was just playing around to see what it was made of for funsies.

i had a 2x7 for a VERY short time on my 30-30AI. the adjustment range was too small to even get it sighted in. a 2x7 burris has been on it ever since.