air venturi avenger 177 heavy pellets?

[OC_]

Has anyone had any luck with really heavy pellets in their avenger 177 over 10.5gr? I have tried a number of heavy pellets/slugs going all the way to 16.97gr but have had terrible accuracy with anything over 10.5gr. It seems like the gun was designed to shoot in the 10.5 range and pretty much anything over the counter at walmart works great. But, i was really hoping to find something super heavy for a high power tune.

 

[SorenDrost]

Tried the JSB KO 13.43 gr slugs without upping the regulator and got good results

 

[OC_]

820 fps is pretty slow. Is this where the accuracy is or was there another reason for such low velocity? 

 

[SorenDrost]

820 fps is pretty slow. Is this where the accuracy is or was there another reason for such low velocity?

Just shot with the settings I use for the JSB KO 10.03 gr slugs at 940 FPS

Tried the JSB Monster 13.43 gr pellets and they shot well at same settings at 861 FPS