I did some searching but did not find any information on what the maximum pellet weight for a Steoger X20 .177. I had gone through a tin of Crosman premier hollow points (CHP) 7.9 and got some predator 8.0 and H&N barracuda hunter 10.34. The CHP's where good, decent grouping, had a few fliers, and seems ok for hunting, needed a few double taps. I then tried the predators better grouping than the CHP's but not by much and where very good for dispatching back yards vermin. I finished the predator tin and am now on the H&N's. The Cuda's grouping just as as good as the predators, I've only hit 2 chippers with the Cudas on dropped on the spot and the other zombied down its burrow. I want to do some more varmit dispatching before I decide on how well they hunt. Well, in much search for knowledge here (thank you for all the information) I came across a few comments concerning max pellet weight in relation to springer power and longevity and possible failure. If the Cudas turn out to be just a good hunter as the predators, will continuing to shoot 10.34 grain pellets with the Stoeger X20 .177 cause harm. I like the predators for their accuracy and damage to vermin but as most people have said they are kinda pricey. So far the accuracy for the Cudas is impressive, I need to get a few more vermin before I can say how well they hunt. But I would like to know if a 10.34 grain pellet in my X20 is ok. I have 2 tins I will shoot. Thank you guys for any information and experience with pellet weight regarding air rifle power.