Variable pumps, variable aim?

[CRex]

Hello, I have a couple of questions about a problem I've been noticing.  It might be equipment related, but I'm pretty new to airguns, so maybe it's also something I'm doing and I'm missing something basic and easy.

Last year, I got a 2289 Backpacker.  I was using the iron peep sight and got a few chipmunks with it - the first was a head shot at about 9 yards in the shadows.  The others were all pretty quick, though not necessarily as definitive as that first one, and I missed some altogether.

For this season (and with my eyes not being great in the first place) I decided I'd put a scope on.  That seemed like a pretty straightforward way to ensure better accuracy.

So, I got the steel breech, and put on a UTG Bugbuster AO 3-9x32.  (I pretty quickly realized that I know about as much about scopes as I do about airguns, maybe less, lol.  )

What's happening is that with 3 to 5 pumps I can pretty much hit a soup can 10/10 till the cows come home at about 12-15 yards or so.  Starting at about 7 pumps however, and definitely by 10, the pellets start to go high (but still group consistently), so that if I aim a couple of inches below the soup can I can usually hit it.  Not very scientific, and definitely not ideal.

I'm mainly shooting the hunting pellet the gun came with, though this happens with the Destroyers and hollowpoints too.

So my first question I guess is, did I maybe screw something up when I put the steel breech on?  Or is what's happening completely normal at this distance - more pumps, more power = flies straighter/further?  I just wasn't sure if the lower pumps would account for the pellet dropping, and I wouldn't have thought at 12 yards or so that it would be that noticeable.  Any idea on what's happening?

Also, I did have some problems with the scope at first (and maybe still am, but don't know it), so maybe my second question is related to the first.  I've been a little fuzzy about how to set the range/AO properly.  I at least have it set so that when I move my head the reticle doesn't swim around and the crosshairs stay fixed on the target.  But for the front adjustment (range)...does this have to be set at the exact distance I'm shooting?  I finally set it at about 20 yards (even though I've just been practicing in that 10-15 yard range).  Will this still be accurate?  If a ground squirrel pops its head up 10 yards away, then runs to 15 yards away, I just want to be covered...I don't think I can fiddle with exact distance estimates/adjustments on the fly and still get a shot off.

Anyway, it might be a combo of the scope and something else, but I just wanted to see if anyone had any suggestions or thoughts to help figure out what might be going on.

Thanks!  (sorry to be so long-winded!)

[DBOdude]

the gun is fine . the more you pump it the more FPS it has and the flatter it shoots . play with pumping amounts and distances over some time and you will be able to stay on or close to vertical zero at different distances .

[jSan22]

Oh yes, thatll happen if the power raises or drops. The POI (point of impact) will drop is the velocity is lower, while it will raise if it gets higher. If you want to sight in a gun for hunting, you would want to pump it to as much as you use for hunting, as the poi will be the same.
and remember, you are shooting a airgun, lower velocities means that pellet is going to be affected by range, wind, and other variables.
these things are the first you will notice if you make power mods to a gun.

[GreyCoyote]

As for POI, its what they said.

The scope issue is a little simpler (or not).  The focus/parallax setting does not change the point of aim.  What it changes is the distance at which the image is in focus and the distance at which the parallax is at a minimum. (Parallax is the cause of the image of the reticle swimming around the image of the target as you move your eye away from the optical center of the scope.)   To minimize parallax, you should set your focus as close to the distance to the target as you can.  But, if you are off on the distance, if you can keep your eye looking down the middle of the image from the scope, the point of aim is still the same.  The problem you run into when your parallax/focus is off it that any movement of your eye away from the optical center of the scope is enlarged proportionate to the amount the focus/parallax setting is off.

Good luck with the Backpacker.  I enjoy mine a lot.  Just watch out for the effect on your wallet of all of the mods you will want to do if to it you stay involved on CAPOF.

[CRex]

I'm relieved the obvious reason seems to be the right one.  At least it makes good sense.

I just never noticed this last year for some reason, although thinking back there did seem to be a "sweet spot" where the peep sight at 10 pumps couldn't miss.

There is definitely more of an art to all this than I imagined!  It's even more impressive that folks can adjust for this with iron sights.

Thanks for the scope advice, too.  I think I understand a bit better.  I won't be teaching a class on it anytime soon, but at least with a small adjustment 10 pumps at 11 - 12 yards was going through the bottom of the soup can last night like clockwork, instead of flying high.

Good luck with the Backpacker.  I enjoy mine a lot.  Just watch out for the effect on your wallet of all of the mods you will want to do if to it you stay involved on CAPOF.

Ha, thanks.  I believe it.  I loved it out of the box last year - it was just the perfect weight and balance.  Now with the steel breech, scope, and er, did I mention a TKO? , it's a bit of a beast.  A lovely beast.  Who wants a reducing friction trigger, a stainless steel safety, a...  Yes, I definitely get the picture.