FN SLP MK1 Full Review

The shotgun, the shotty, the gauge, the classic “big bore” gun in nearly every man’s (or woman’s) collection. Must of us own at least one and most of them are chambered for 12 gauge, 2-3/4″ shells if we’ve ever used them to bring home dinner or planned to use them for the more serious purpose of putting an end to unlawful violence. They can be had in bolt-action, pump-action, over-under, side-by-side, full and semi-auto configurations. It’s the latter of all of these that I find myself using most of the time. And that is what I have recently acquired in the form of FN’s Self Loading Police (SLP) MK1 shotgun with plans to use it in 3-gun matches in the near future.

The FN SLP shotgun has been on the market for a couple years now and there have been several revisions and variants introduced in that time. It is kissing cousins with Winchester’s SX3 shotgun as well as Browning’s Silver line. Mind you, they aren’t absolutely identical but, they are close. Really close. All three use the “Active Valve” piston system with the Browning version supporting the lightest loads (1oz) of the three. All that said, the different brands are marketed toward different shooters with the FN SLP aimed specifically toward the 3 gun, defense, and law enforcement markets where as the Winchester and Browning offerings focused on hunting and trap/skeet crowds.

img_0001_02As it ships, the SLP MK1’s aluminum receiver and gas operated action come attached to a 22-inch, 12 gauge barrel with a 3″ chamber. The barrel features a hard chromed bore, rifle sights (flip-up rear) with a fiber-optic element up front and a weaver pattern, cantilever rail overhanging the receiver. The barrel uses Standard Invector standard chokes, also common to Browning and some Winchester shotguns. Mine shipped with a “modified” choke installed and included a second, improved cylinder choke. Slung under the barrel is the piston and magazine tube offering an extended capacity of 8+1, 2-3/4″ shells or 7+1, 3″ shells rather than 6+1 or 5+1 as seen in the original, 18″ SLP. The furniture is all black synthetic and all metal surfaces are matte finished as is common with all things “tactical” these days but, if you want to spend some extra coin on the “Competition” version, the gun can be had with nifty “blue” anodized surfaces. It feels big. It is big. Overall length is 43″ with overall weight stated as 8.2lbs.

Something of note is the owner’s manual clearly states that two gas pistons ship with the MK1. The first, a red-rimmed “light” piston is noted as having been installed at the factory and is intended for lighter loads, 1-1/2oz or less. A second, black-rimmed piston, to be installed by the owner, is meant for heavier loads, over under 1-1/2oz. The manual states, “They are not designed to shoot the lightest factory 7/8oz and 1oz target loads…” But I quickly noted my box had no second piston laying around in it. When I disassembled my shotgun for inspection, cleaning, and lubrication, I found an odd “gold-rimmed” piston. According to FN, this improved piston was added back in 2013 as a “universal” piston to services all loads, 1-1/4oz or heavier. None of that common, cheap, 1-1/8oz bunny fart stuff will do. Only expensive, big baller loads need apply. The FN SLP MK1 is no cheap date.

So how does it shoot? Well, the first tests were underwhelming. Each weekend between December 27, 2014 and January 17, 2015, I struggled with getting the gun to run reliably each weekend. Having read all sorts of hype about how reliable the SLP is supposed to be, I experienced little of the versatility and “war ready” reliability that so many members of the gun media claimed to have experienced with guns sent directly to them by FN. We only managed to fire 16 rounds without a stoppage in the first session. Thinking I might have missed something in the initial cleaning, I tore the gun down a second time and found a spot of heavy lacquer caked to the underside of the top half of the two piece bolt that may have contributed to those early hiccups. But even after that thorough second cleaning, the gun didn’t run when lubricated as directed. The manual clearly states that one completes cleaning of the gas system, “by applying a very light film of oil to all parts for protection and lubrication.” Conventional wisdom says this area should have minimal lubrication if any and there are posts in the Brian Enos Forum and other places indicating that the piston needed to be bone dry to run reliably. With my copy of the FN SLP, thin film or dry, neither seemed to work for more than 15 or 20 rounds before the gun would fail to cycle. Even with a steady diet of 00-buck, the gun would quickly build up enough fouling in the gas system that the piston stroke would become truncated and fail to cycle the bolt. Failures to eject would come first. Eventually, becoming failures to extract and finally, the gun became a hand-operated, single-shot affair.

After three weekends of frustration/failure, I decided to try something different after reading at least one account of a shooter finding his SLP worked better when the piston was wet. So after one more cleaning, I liberally applied M-Pro 7 Gun Oil LPX to every moving surface of the gun, including the magazine tube and piston. The gun was practically dripping wet with oil when I met friends at a local range to shoot trap. On the way to the range, I also made it a point to find a minimum 1-1/4oz load suitable for clay birds at my local Academy sporting goods store. That load ended up being Remington Express Extra Long Range, 2-3/4 inch, 1-1/4oz, #6 shot. I also picked up Federal’s 2-3/4 inch, 1-1/8oz, #7-1/2 shot ammo for testing of a lighter load.

img_0001Once we got started, I was pleasantly surprised to see the gun ultimately ran through 100 rounds of this ammunition without a single hiccup. For once, the gun seemed to be living up to its reputation. Round after round, the hammer fell, pellets flew, and clay birds were turned into powder. Finally, it seemed like the gremlins were gone and it seemed that the combination of an appropriately heavy load and liberal lubrication of the SLPs gas-system was making the difference. Curious to know if it was just a question of lubrication and not just the gun’s inherent sensitivity to lighter ammo, I decided to switch to the lighter Federal load. The gun instantly became a single-shot, bolt-action as the lighter Federal load wouldn’t cycle the bolt enough to extract, let alone eject, a fired shell. Another test session after the trap outing showed the gun happily digested a mixed bag of ammo from #6 shot to 4-buck, 00-buck, and slugs. But as mentioned earlier, bunny fart loads simply will not do. Nothing under 1-1/4oz will cycle the bolt. That’s just a fact of life with the SLP MK1 and it’s “improved” piston. If you’re interested in running light target loads, the Winchester SX3 or Browning Silver might be the better option. The nearly identical gas-systems of those models are better tuned for lighter loads with the Browning boasting the ability to cycle 1oz loads.

Gas and lubrication issues aside, I liked the gun once I got it running. The Weaver rail mount of the 22-inch barrel is almost a funnel for the eye, leading to the bright, fiber-optic, red front sight. There is also a separate, flip-up, rear-sight with give you a full set of rifle sights for use with slugs. The SLP’s recoil, even with heavy 3-inch magnums, softer than any other 12 gauge I’ve shot in recent memory. While shooting trap, I had the chance to compare the SLP to a Benelli M2 and it’s Franchi Affinity sibling. With the same #6 shot loads, the SLP is softer recoiling. Recoil with the 11-87 Police that I also had on hand was comparable to the SLP but, the SLP is quieter by comparison. You can physically hear the Remington’s action shucking every round while its mounted where as the SLP is solid and silent by comparison. While its proportions make for a big gun, it mounts/points naturally, and the furniture provides an aggressive, yet comfortable grip. Tandem-loading (two shells at a time) is relatively easy to do with the gun in stock trim but, some 3gunners say one must weld-up or replace the carrier as well as enlarge the loading port to make this process smoother/easier. I will spend a bit more time with the gun before electing to make such a change. At the moment, I find the SLP in stock trim to be significantly better than the stock port and carrier arrangement of Remington 1100/11-87 models to which I am accustomed. 1100/11-87 loading ports typically come pre-sharpened from the factory and neither their stock carrier nor the release button facilitates quick charging of the tube.

Overall, I will say that if you have an SLP that runs the way you want, keep it. If you’re considering one for your next auto-loading shotgun, take note of the issues I’ve had with my copy but, realize that I’m happy enough now that I’m not jumping on the pizza gun bandwagon just yet. Also take note that the Winchester SX3 and Browning Silver are nearly identical but, they apparently can cycle lighter loads while also accepting 3-1/2 inch shells. I will not claim the gun is the best shotgun ever but, so long as its fed appropriate ammunition and sufficiently lubricated, it runs as designed and is enjoyable to shoot.

3 thoughts on “FN SLP MK1 Full Review

    • It certainly wasn’t my intention. That is simply the oil I had handy at the time. I’ve also used Breakfree CLP, Tetra, TW-25, Militec, Mobil 1 sythetic 5w20 and Castrol 90wt gear oil as gun lubes over the years. The honest answer is THEY ALL WORKED. I only once mentioned the other brand that one time during that phase of testing. But, if you want to see it as an endorsement/ad for them, go ahead. It worked just fine but, I wouldn’t say you have to use it. Heck, if you’re really in a pinch, you could, in theory, dunk the gun in transmission fluid and expect it to run for at least a little while.


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