As I noted in my Green Ops shotgun class AAR, I am a HUGE fan of my SDS S4 shotgun. This is a Benelli M4 clone that, unlike the previous M2 and M3 clones, is damn near perfect in. Read on for some thoughts, and how I upgraded mine.

Let’s talk about the SDS S4 vs the SDS Tac-12 for a second. The primary differences between these two shotguns are:

1. The Tac-12 has a trigger guard shape closer to the real Benelli M4 trigger guard. The S4’s trigger guard is larger and more similar to other Turkish shotguns we’ve seen.
2. The Tac-12 has a proprietary recoil spring tube designed for use by the Turkish proprietary collapsing stock, and is not compatible with any Benelli M4 stocks. The S4 has a more Benelli-like tube that has no position cuts.
3. The Tac-12 is assembled by Sulun; the S4 is assembled by Aksa. The parts are made by someone else entirely to the best of my knowledge. I am unsure whether Sulun and/or Aksa have to do their own heat treats.
4. The Tac-12 supposedly has a better finish than the S4.

Basically, you want the S4 if you’re going to put a Mesa Urbino on it, and the Tac-12 if you’re going to use the Turkish-made proprietary collapsible stock. The S4 is considerably cheaper than the Tac-12, and I didn’t need a collapsing stock, so I went in that direction.

The first thing you should do after buying one of these guns is to put a couple boxes of buckshot (3″ preferred) through it to make sure the heat treat was done correctly. Just do a bunch of tube dumps. Don’t even bother with a target, just hit the berm. If you have cycling failures, take note of the ammo, but you will be correcting these soon anyways. Crack the gun open back home. If the pistons and bolt carrier have maintained their integrity and not gotten deformed, you’re in the clear. If not, stop what you’re doing and RMA to SDS. They will take care of you.

Assuming you have a properly heat treated gun, the next step is to swap the extractor and extractor spring for a true Benelli setup. I don’t think the factory extractor is all that bad, but the spring is not terribly strong, leading to extractor slip and cycling problems with some shells (Winchester Super-X in particular). Since you have to remove the extractor to replace the spring, it simply makes sense to replace both with a known high quality part. You can see how to do this on the Internet; it’s exactly the same as a normal Benelli M4.

Removing the stock is easy. You will need an 8-1.25x25mm bolt for your Mesa Urbino stock. This is easily available at Home Depot. Consider throwing a teensy bit of thread locker on it, or maybe a lock washer.

Now, the tube… I replaced the entire magazine tube. It was far easier than I thought it would be. I used the Dave’s Metal Works 7-round tube (US-made, so good for 922r) and a random US-made follower. To remove the tube, I simply field stripped the gun, took out the tube internals (use lock ring pliers), and then hit the inside of the old tube from inside the receiver with a butane torch. It only took a minute or so before I disabled the thread locker and I was able to twist the tube off with a pipe wrench. After that, you just thread on the new tube (use a bit of blue thread locker), insert the internals, and you’re good to go. Easy.

My experience is that after-market charging handles like the TTI need to be turned down a teensy bit to fit the M4. They will tap in with a mallet as is, but you will have trouble getting them out. I personally don’t think the factory charging handle is all that bad, and would recommend not even bothering.

After doing all this, I’ve got a gun I’m pretty happy with. The only other upgrade under consideration is an extended bolt release like the DMW Speedbar, because I don’t love how small that button is (the Stoeger M3k has completely spoiled me).