Remove the hopup/inner barrel assembly and look down the barrel, hopup end. Adjust the hopup wheel and see if the bucking is moving up/down and the rubber bump is visible in the barrel. If the bucking isn't moving up/down, there may be something wrong with the tension arm. If it's moving, then the issue may be with the rubber's nub being damaged.
Test fire your rifle outdoor on a sunny day so you can watch the BB's trajectory. Adjust hopup until it shoots flat for 40-50m. Too much hopup will cause the BB to fly out and curve upwards. Too little, and it will just drop.
There is also the possibility that your sights are just off - 50-60 ft (10 m) is pretty damn close, though. You should be hitting your target at that distance.
Based on your description, it sounds like your airseal is solid, and since the rifle's a BA, I can't imagine a double feeding issue.
VFC SCAR-L - VFC SCAR SSR - KJW Hi-Capa 5.1 - CAW M79
The Three Sisters - WE G39 E/K/C
Originally Posted by kalnaren
Stalker stays where he is.
His BB's fly across the country to hit their target.