Alloy pellets

[illinois]

Will light alloy .177 pellets damage the piston on a X10. What pellet works best.

[Chevota]

I've tried about every pellet made for all the calibers and my best luck is with quality lead pellets on the heavy side. Kodiak or Baracuda pellets are always a good choice. JSB Match Diablo Exact at 8.4grns have a little extra weight than a standard pellet and are very high quality, also inexpensive; 500 for $10. That's about the best quality pellet for the $ you can get.
The only real way to get the best pellet is to try them all, it sucks but it's true. China guns are more picky because of the quality level, Guns like a FWB with a choked barrel will shoot about any pellet accurately.
If you want a hollow point there is only one; the Crow Magnum. It's the right weight for the more powerful guns, and it actually mushrooms! What a concept! The other hollow points pass right thru a crow or rabbit with little if any mushroom, the Crow Mag open up and really does some damage, you can even hear the difference on impact. (Update: My fault for not keeping up with the latest cheapie pellets, but; I just got the Crosman Destoyer pellets in .177 and these things are kinda wicked! The design has a big mouth like the Crow Mag, but a bit thinner and lighter. I haven't tried them on an actual critter yet, but in clay it did open and did so easier. My guess is this is probably better on very small critters like Sparrows/mice or shooting raw eggs etc, where a Crow Mag's design is better for larger stuff. The point in the center is a cool looking touch, and I think the name is very fitting)

Basically the only real use for an alloy pellet (imo) is to see how fast your gun can shoot one. They are harder on the gun because they reduce the air cushion effect, and the more powerful the gun the worse it gets. They can also break the sound barrier and even if they don't break it the extra speed will still reduce accuracy, that's why the most accurate guns shoot around 550fps. I admit that the gold ones are cool looking and being oil free is nice, but you can also get some lead ones in copper plate and mess free.
Don't ever use a cleaning pellet by itself, it's much lighter than the alloy ones and is basically a dry fire so the gun and seal really take a hit. Just use a lead pellet with it, put the cleaning pellet before or after the lead pellet and you're good to go. As long as the weight of the lead is in there your piston is safe.
Don't ever use those plastic pellets either, again they're too light=piston slam..
One more thing; look at the pellets themselves, if they're deformed or the cast is poor leaving an uneven pellet shape and weight then pass them up. You want each pellet to be the same for best accuracy. These aren't a kids $30 plastic smooth-bore pump gun, these are good quality rifled guns and need the best quality pellet to take advantage of that. The crummy ones are good for breaking in a gun tho...

Hope this answers your Q and anyone else's.