In the simplest of terms, my copy of the FN SLP has turned out to be a bit of a queen. By that I mean it’s very pretty as shotguns go. It’s got all the sexy parts and proportions. But in practical terms, it will only work as desired when clean, heavily lubed, and only large loads need apply. The gun ran successfully today through 100 rounds of Remington Express Extra Long Range, 2-3/4 inch, 1-1/4oz, #6 shot ammo with zero failures. Thinking the issue may now be just a question of running heavy enough ammo, I switched to Federal’s 2-3/4 inch, 1-1/8oz, #7-1/2 shot ammo. Federal wouldn’t even cycle the bolt enough to extract, let alone eject a fired shell.
At this point, it looks as if the “trick” to getting the SLP to run is liberal lubrication of the exterior of the magazine tube and the piston that slides along said tube. This time around, I used M-Pro 7 Gun Oil LPX. It’s on every moving surface of the gun and applied liberally. FN’s own manual does indicate one should put a “light coat” of oil on the piston. That, in and of itself, isn’t all that weird. But the gun wasn’t running and in talking with other SLP owners, I found several saying the magazine tube needed to be all but wet. That instruction simply struck me as odd (heavy lubrication of the gas system itself is not normally required) but, previous sessions with the gun and only a light coat on the magazine tube obviously wasn’t working. So I decided to try running the gun dripping wet and was pleasantly surprised when the gun ran flawlessly for the first time. As the old saying goes, an oily gun is a happy gun.
It’s worth mentioning that earlier copies of this shotgun were sold with two pistons rather than the one mine came with. The “red” piston installed at the factory was rated for lighter loads, those of 1-1/4oz or less. A second, “black” piston, was meant for loads exceeding 1-1/4oz such as 00-buck or slugs. Most of the folks who seem to be happy with their SLPs are people who had them before FN went to their current “gold” “universal” piston which is rated for loads from 1-1/4oz or heavier. What I found today is that is absolutely must be 1-1/4oz or heavier for the gun to cycle and that if I ever want to routinely use this shotgun for trap, skeet, or 3-gun, I’ll need to get my hands on a “red” piston.