This is a discussion on Gas Pistons? within the FN Shotguns forums, part of the FN Rifles & Shotguns Forum category; Got my first FN yesterday, knocked it down and did a very thorough cleaning. That's when I discovered there was only one gas piston (heavy). ...
I couldn't begin to tell where I found it, but somewhere on FN's site is the information I was looking for. The web site says there are 2 pistons, the owners manual says there are 2 pistons, but according to FN the late production (they don't say when) SLP shotguns have only 1 gas piston.
Since my range is only a short walk from my house I did a little familiarizing, shake down, break in and in general getting to know the SLP. The best shotgun I've ever owned, probably not. Best squad car shotgun I've ever had, maybe maybe not. Best house gun I've ever had, don't know yet. What I do know is that the SLP works with very heavy loads and very very light loads. Several hundred rounds down range so far and not a single malfunction. Not even my venerable old 870 was 100 percent, I actually short stroked it once. The SLP is capable of filling many different roles and doing them all quite well. It's not the softest shooting shotgun I've ever had but even with the very heavy loads it's tolerable. Only time will tell if this becomes my all time best, so far it is doing well.
There is only one piston in the later models (I bought my SLP two years ago). I had trouble with light loads and did the Surecycle mod (great people by the way). I haven't had a single issue since then, regardless of load.