I have a couple .25 cal Dominators. If they get to grinding, open it up and clean it out. Its probably just some loose metal bits or grit. I have one that I need to do that to (again).
The rifles are solidly built and easy to work on. Mine are accurate but too jumpy for me to shoot very accurately. So, it takes a lot of practice to get used to shooting them. IMO anyway and that's not worth much. There were some ,22 cal Dominators made with Lothar Walthar barrels. I think AoA has some and that's why their prices are higher; those are the ones really worth having.
If you get one, take it apart, clean it thoroughly, and relube it. Its been packed away for a few years. Don't shoot it without at least cleaning the barrel. After cleaning mine, they are smooth operating rifles. I don't shoot them very often but when I do I get re-impressed each time.
If you are getting the .22 cal, its a good idea to detune it. If you are getting the vortex version, its very easy to do. The gas piston in it is designed to have its internal pressure adjusted by the end user. You just need a standard pcp handpump. It has a bleed screw and a fill port. Very nice.
Also the length of the cocking lever can be adjusted. Just remove the hand grip on the cocking lever and you'll figure it out. There's nothing in the manual about it.
For $100 new, I think its a good deal. They aren't the prettiest rifles but they are a well built underlever. I wouldn't bother with the Proxima or other repeater models. It is recommended to get a set of seals- breach seals and piston seals. You'll probably want to at least replace the breach seals.
