I had a gamo whisper a few years ago, lost it in the divorce it was super easy to install the scope and sight it in.  decided I wanted an upgrade and went with a piston driven one, just got it in brand new from amazon.  no open sights but does come with  scope.

sighting in at not even 20 yards, first shot is 3 in high and 3 in right.  adjust scope 12 down and 12 left and now its 3 in right and 5 in up.  wtf.  no more adjustments and take a few shots and im getting nice 4 inch groups at not even 20 yards.

scope rings are extremely tight on the picatinny base, and i torqued the rings around the scope itself about like i usually have done with my AR scopes in the past.  scope is  definitely not moving around on the rings or base.

wtf?  now, I am using some really old pellet ammo, game match diablo, same ones i used to use in the old airgun i had in 2009.  they are kinda flat in the head.  but does different pellet type really make this much of a difference under 20 yards?


eta:  for comparison the gamo 22 whisper i had had practically zero noise for the spring action and a good PFFFFFFTTTT subsonic barrel exit noise.  this one has zero barrel exit noise but a fairly loud piston noise, about like a hammer coming down hard on a nail.

Clean the barrel real well.  They are often oiled from the factory.  Try a dome pellet, the flat nosed are target pellets that operate best at shorter distances.

doesnt seem to help, cleaned it all up real good.  wire brush and a few patches.  still bad innacurate, even with some new pointed pellets.

First of all, don't use metal brushes in air gun barrels.   Only use patches, and the fouling is bad or you want to polish the bore, sparingly use use J-B bore paste.
When you load pellets do they fit tightly or loosely?  Are you sure the breach seal is good?   To confirm, when you shoot a pellet, lay a tissue on top of the breach, see if it moves when you shoot.
Normally when you see this much dispersion, I look at the optics and mounts first, then clean the bore, then go through as many different pellets as I can.   Also remember your artillery hold with that gun.

ok thanks for this.  had to look up artillery hold, the vendor did mention this as well in the email i got from them, wasnt aware of this but dont recall the concept on my previous .22 gamo subsonic whisper.  from vendor:

additionall though, the trigger on this is absolutely crap.  an EXTREMELY long pull that requires a good bit of force during its entire length.  id be glad to pay to get a decent trigger in this, im sure itd make it loads more fun, is this possible?

I don'the believe there are any after-market triggers for this.  There are tuners out there who might take this on.  I'd post this on the Yellow and see if anyone recommends a tuner to you.

yea i took it apart and this trigger assy doesnt appear to have that ring that can be replaced with a bushing like the others. but looks like im not totally out of luck  ebay

There is an after market trigger, I found mine on Google. I think called the gold trigger

Super easy install and makes it far more shootable.

Not sure what the issue is but honestly I'd switch that scope out first.

just to test. Most of my air gun issued come down to the scope. My guess is your scope innards are loose.

Eta: check here for trigger

Charlie the tuna trigger

1/4" adjustments at 100 yards are 1/20th" at 20 yards right?

Yep,  It's 1/5th the distance.  You multiply the denominators and you get 1/20th of an inch at 20 yards.

My advice is to get a fixed barrel underleaver like my Gamo Whisper CFR. Like you, I was needing minute-of-cowbird at 30 yds and several breakbarrel guns were tried and simply not doing it, no matter the pellet. So, I popped for the CFR and sitting on a rest I can cloverleaf at 30 yds (head shot) with the 10.5 gr Gamo Silents. Of course, youre talking a $250 gun vs $75 guns.