Have not used any LR subs, but I have shot CB's from CCI and in a rifle length barrell they made less noise then my Sheridan pump air rifle and my RWS air rifle with a bit more punch then both of them. The RWS is the most accurate of the bunch.
As mentioned, the CB longs from CCI are nice. I have used them to lower the population of tree rats in my yard. Very quick kills at 30 or yards.
I have tested them in benchrest 22 rifles and accuracy is very good.
Best of luck.
The longer the barrel the quieter eather will be. My favorite round for squirrel hunting is the Remington Sub-sonic. I have found them to very accurate in most of the rifles I have tried them in ( even though the standard devation isn`t the best) and the heavier HP bullets hit alot harder.