hi buddy
i think your right you need to know what your rifle is putting out!
if you havent got a chronograph?then take it to your local gun shop,and they will chrono it for you.maybe for a small fee.i have a chrono so thats just a guess the fee!
or if there is some one on here who lives close to you,with one may be they will help ya out!
but your dead right on wanting to know,seems you have bought it second hand.can you ask the person you bought it off?
regards
davy