I've been having a boatload of fun shooting my Xisico Sentry's, I now have four of them, one that was given to me by a factory rep and three of them since. The one that I got from the factory rep is a .25 that I've since modified and it's shooting my cast slugs up to 50fpe. I know that some guys are even modifying them up to 100fpe which basically for me is a little overboard for a small caliber but to each his own.
These guns are super reliable but I recommend a person to go through them completely when they get them. They're an excellent choice for a tinkerer because of very well designed platform. The valves in them are about the safest/toughest I've seen so far. They aren't regulated but once you get them adjusted where you want them they are super accurate in both .25 and .22 and will deliver a good long string. Basically the only modifications that I've been making in mine are drilling out the ports, deburring whatever needs it and a thorough cleaning replacing original lube throughout with better lube.
This one is my latest one which is actually one of the original's made back in late 2016, I bought it from a fellow member on GTA and it's always a lot of fun out in the woods hunting and doing a little plinking too.
I second this gun. You don't hear much about them, but the Xisico 705 Sentry is really a nice piece. I Love the look and performance. Check out Airgun Dectectives on Youtube.