How to find out how you are doing:
1. Jack is correct- you must first learn the accuracy of your rifle by shooting it “from the bench.” That means get a table and some good solid things to rest the forearm of your rifle on, such as some sandbags or bags of rice, and fire off a group.
The best shooter in the world can’t shoot better than their perfectly held rifle.
The gun has its accuracy which you may be able to improve by testing the number of pumps you use and the type of pellet you use. Perhaps one type of pellet will be more accurate in your rifle than others. Perhaps five pumps is more accurate than 6. Rifles are complex and exactly how the pellet leaves the barrel depends on so much, right down to two identical 880s might not like the same pellets.
Your power line 880 is a pneumatic gun, you don’t need to worry about the complexity of a vibrating piston/spring and how you hold a rifle with reverse recoil.
The shooter has their wobble area. That’s how well you could shoot with a laser beam mounted on your gun that scores when the trigger is pulled. That’s the practice practice practice part.
When trying to find out how you are doing, try shooting at conventional targets and ranges. That is, 10 meters is the internationally accepted distance.
Get some official 10 meter targets. I bet you can print them off the interwebs.
Then score yourself. See what your score is compared to what other guys get. Low 90’s is pretty good.
You are shooting at pretty much “way the hell out there” range. Things like wind are coming in to play.
Once you are shooting a while at 10m and keeping your scores... you’ll want to find a local club and shoot some league shoots.
It’s fun.
And as for ammo, don’t shoot high velocity .22 ammo.
Try CCI standard velocity, Aguila regular ol velocity, CCI mini mags (not likely but sometimes) and if you don’t get good accuracy out of one of those types, i’ll send you a tin of rws pellets.
