Scope Sighting problem

I bought a Benjamin Trail NP Nitro Piston a few years ago that came with a Centerpoint scope. I could never get it sighted in properly and it just sat in the safe. I recently got it out of the safe and put a Barska 3-12x40 AO scope on it. I am having issues with it as well. I have the scope up/down screwed in as far as it will go basically and it is still an inch high at 10 yards. It started about 16 inches high and this is as close as I can get with all the adjustment the scope has. The Picatinny rail is built on to the gun so there is no adjustment there. I have sighted in dozens of high powered rifles over the years and have never had a problem like this. What could be going on? Any help is appreciated.
 
Thanks for the response John. I think the airgun might have been slam fired by my son, but I never would have thought this would cause any harm. I figured the latch held it where it was supposed to be. Looks like I might be wrong. Take a look at these two pictures.

This is on the receiver showing the gun level.


This is on the end of the barrel.


I am guessing this is toast and can't really be fixed if what I am showing is the case.
 
I bought one of the refurbished "Ruger" model 34 clones and with the scope cranked all the way up it still shot 12" low at 10 yards. I took it apart and chucked it in the lathe, then proceeded to bend it a bit at a time. Took quite a few bending trys to get it to shoot straight. It is not too difficult to do. Hardest part is finding something solid enough to hold the breach end of the barrel, lathe is plenty strong.. All totaled I bent it nearly 3/8 inch, but it shoots 1/2" groups at 10 yard, which is good for a 90 dollar rifle. Don't be afraid of bending it into shape.