I'll just clarify as people do seem to get confused...
The MSR slam fires due to two reasons. The first is that the piston is made of plastic. When used with even the stock sears the plastic piston catch wear down and stops catching the sear.
The second issue is the piston sear itself. It is made of the worst metal i've ever seen used for a sear. Worse than the JG Bar10. It wears quickly even with the stock piston.
So with both the stock piston sear and piston, they wear each other out and cause slam firing. If you replace one part it might resolve the issue for a few mags but the slam firing will return. You must replace both.
However that's where the problem lies. At present, there's no readily, widely available replacement piston sear for the stock trigger. So even if you use the Ares upgrade cylinder set, it will still fail because the piston sear hasn't been replaced.
I have many happy customers and i too have upgraded and use in my own MSR the following parts. fyi i'm not suggesting you buy from us, buy from wherever you like but this will help you identify the parts required:
Trigger:
http://www.airsoftsniperparts.com/ap...s/show/4297780
Piston:
http://www.airsoftsniperparts.com/ap...s/show/3749116
Spring Guide:
http://www.airsoftsniperparts.com/ap...s/show/2983108
M170 Spring:
http://www.airsoftsniperparts.com/ap...s/show/3179979
This setup will get you around 540 fps so you may need to clip the spring depending on your site limit.
Other parts are VSR compatible such as the hop bucking, cylinder and cylinder head. How do i know this, because i use them in my own MSR
For a full range see:
http://www.airsoftsniperparts.com/ap.../971866?page=1
Like i said, you don't have to buy anything from us but hopefully you'll find this information useful.