I finally got around to try to fix the slam firing on this gun, I purchased the shs vsr sear, the curly one( never remember the correct name, trigger sear I think) it fits fine and for a short while, well half a game had no probs. however now slam firing again. Looking at the piston sear it is very well worn and can't find anything that looks the same. As for upgrade kit, you can purchase direct from ares, I did and not a bad price. Also if you contact them with the part number they will send you the replacement parts as well. But not free of charge :-( but still you can at least replace the parts that have gone. I had asked if they will be doing reinforced sears, but was told not at the moment. Shame really as the sears are crappy pot metal and as such in having to speak to done milling people to see if they can make them. This is one expensive rifle that at the original price should have had a decent trigger box.