I have had decent results out to 40yards. They are not as spot on as the regular 10.34's, but are acceptable, within reason. This is just my experience at my limited range. I have shot two tins and have come to the conclusion that 35 yards and in they are accurate and pack a punch.
I have seen several mentions of them not expanding well. I have observed the opposite. They open up and spread out impact shock. I tried many types of target materials and ranges.
As you can see in the photo the range was 25 yards for the wax cast of the impact area pic,hard earth clay was used as target material. The pellet is in the location it stopped in the wax pic.
Actual pellet shown in close-up (with an unfired pellet as reference)
Im just a do it for fun, test stuff and such. I'm also financially challenged so have do all my stuff on the cheap
GAMO Magnum 10.34 HADES 975fps @muzzle, 875fps @target. Used Caldwell Chronograph at the stated ranges with result being the average of over 15 shots.
Have fun shooting