Build An 11 Shot Mossberg 500 – Detachable Mags, No Gunsmith Required!

Guns America – by Paul Helinski

Adaptive Tactical Sidewinder Venom Kit
From $199: http://adaptivetactical.com/sidewinder

I have come to realize that some products are worth figuring out. That was the case on my newest trunk gun project, adding an Adaptive Tactical Sidewinder Venom kit to one of my Mossberg 500 shotguns. The kit did not go on easy, which I’ll explain, and I even had to send my gun into the company. But it turned out that the issue was my misunderstanding of the directions, and a miscue of information on the phone. If you have considered buying a KSG, or some other high cap shotgun, yet you have an otherwise unused Mossberg 500 in the safe, I would seriously consider this kit, which starts at $199 and goes to fully decked out at $399.  

My review is of the base model with a standard forend, but as you’ll see on the company website, there is now a version with an optics rail forend, as well as some current camo pattern options. The Adaptive Tactical Venom Sidewinder is a detachable magazine kit for the Mossberg 500/Maverick 88 shotguns, with the 6 round mag tube. And after some unnecessary trepidation on my part, it works marvelously.

The Sidewinder Venom is not a new product. It has been around for decades and was previously manufactured under at least a couple other monikers. I actually have an original Knox Sidewinder kit from the mid 90s that I never installed. I bought it from a friend (Hi Cory!) during the ban era and never got around to figuring out why I thought I need it, but after installing this new version of the kit I now understand. It turns an already excellent self defense weapon into a absolute beast of a self defense weapon.

The “why do I need this” question immediately arises for anyone who knows defense shotguns, because a regular Mossberg 8 shot Persuader, and the military 590A1 Tacticalversions of the 500 are incredible firearms. But they are somewhat unwieldly due to the length, and all of the weight of the shells in the front part of the firearm. As a trunk gun or home defense gun, I have always kept my 6 shot 500 with a pistol grip at the ready, as opposed to my 8 shot guns (I have 3), because it is quick, light, and has a lot of punch in 6 rounds. Then, since I reviewed the Mossberg FLEX, with the breacher barrel (which I decided to buy from Mossberg), I have switched to that as my goto gun instead of my original 6 shot 500, which was one of the first firearms I ever owned.

So it was with great trepidation that I decided to convert this gun into a Sidewinder mod. And at first I was disgusted with myself because it initially didn’t go well, as I’ll explain. But first let me explain some things about the Sidewinder that I was incorrect about.

1. It is not for NFA “Short Barreled Shotguns” – I had actually almost given my old Knox kit that you see here in the pics to a friend of mine who has a registered Mossberg 500 SBS. Those guns usually have a cut down 3 round magazine, which to me, coupled with the ridiculous muzzle blast, is completely useless. A detachable magazine would be a great aftermarket accessory, but the Sidewinder replaces the 6 round mag tube, and can’t be shortened.

1. This is not a fringe nerd product – These days there are far more firearms and accessories out in the LE and military field than are designated “official use.” I know for a fact that the Adaptive Tactical kit is a military product, because when I sent my gun to them UPS **lost it** and it would have otherwise never have been found. But…Adaptive Tactical is a military supplier, so when the notified UPS that they would have to report it to FBI on those grounds, it was found in less than a week.
2. I like it better than my KSG – This is really hard for me to admit, because I absolutely love the KSG. But my hands have been used to the Mossberg 500 for decades. When the KSG first came out, I was an early reviewer and I fell in love with the gun, which I also bought. But as time went on, I found that I felt more comfortable keeping the Mossberg as my goto. I don’t need to always carry 15 rounds in my shotgun, but being able to snap on an extra 10 round mag is a great feature.

Perhaps the biggest advantage to the Sidewinder kit (besides the price because the KSG is still seldom discounted below MSRP), is that you don’t have to keep the gun “loaded” in your car or house. In many states, having a loaded shotgun in your car violates state hunting laws, and in some states it is even a felony, even if it is in a case. If you live in a state where the ammo can’t be in the same car compartment as the gun, the Sidewinder allows you to keep the gun empty, yet have 10 rounds and more mags at the ready in your center console. If you have kids in the house and you want to keep one gun out of the safe for home defense, it’s the same thing. You can keep the mag in a separate location, and click pump, she’s good to go.

Now onto the installation. What an ordeal, but I genuinely think it was my fault.

To start, you have to take apart your Mossberg 500 as normal, including the two pins to take out the trigger assembly, and the bolt rails, plus the two metal “finger” shell retainers that keep the shells in the tube while pumping. Remember those darned shell retainers.

Then you have to unscrew the mag tube, which will not be easy, especially if you don’t have a vice set up, which I don’t. But I was able to use a piece of thick leather and a plumbing wrench in the same way, with channel locks to bread the tube free, because I don’t plan to reuse the tube. If you want to keep your tube and receiver both pristine, it would be a good idea to use a vice and probably thinner leather with channel locks or a pipe wrench to gently break the surprisingly stubborn tube free.

Then you screw the Sidewinder assembly into the mag tube hole, but do so very gently, and watch the front of the hole, where the shells eject from the tube, to see where the Sidewinder tube comes to the end. DO NOT FORCE THE TUBE TO GET IT TO LINE UP WITH THE RECEIVER. That was my first mistake, because I didn’t understand this. Mossberg does not have a standard thread pattern on that threaded hole. It starts where the person working that day decided to start it, so the Siderwinder magazine well will not line up to straight at exactly the same depth every time. And since straight is straight and can’t be modified, what has to be modified is how much threaded tube you screw in.

Adaptive Tactical includes a piece of sandpaper to sand away some of the magazine tube, so that it lines up straight without forcing the tube in further than it needs to go. So when you get there, if your mag well isn’t straight, back it out, sand some off, then try it again. And do that until it is straight and the tube is clearing the edge.

I didn’t do that. I forced it, and that swaged the end of the tube into a cone that would not allow the shells to pass. My remedy was to dremel away the swaged portion, and it worked out fine. But this was only the first of my problems. See the pictures. This issue is easily avoided by being patient, and backing out the tube, then sanding, until it fits correctly.

My next issue was that I didn’t understand one of the key directions. There are those two metal fingers that hold then release the shell from the magazine as you pump. The directions, which have been rewritten over the decades, are very clear that you only install one of them, but for some reason, it didn’t register what a “shell stop” actually is. So I had this installed kit, but the shells just weren’t feeding correctly. A phone call to the company didn’t resolve the problem, because I didn’t call the little metal fingers “shell stops” so they just couldn’t figure out what was going on with the product. Then, after sending the gun in (and having UPS lose it and find it), they were like “oh yea that’s the most common issue we deal with when gunsmiths try to install the kit.”

You don’t need a gunsmith to install the kit! You just need to actually read and understand the directions, and it would help to have a vise handy. In trying to figure out my issue, I tried to turn the inside shell follower around, and the retainer shim became confusing, but I never had to mess with that at all.

Now that the kit is installed correctly, I took it out today and put several boxes of both low brass bird shot and high brass buck shot through the gun. It didn’t budge, and though I would say that the 500 is maybe a little more lubrication sensitive (I usually keep my 500s dry), the Sidewinder Venom worked without one failure. I was able to test the $35 straight 5 round magazine, and the $90 drum 10 round magazine, which can be clicked in either left or right leaning. I didn’t get the $50 10 round straight mag, but I doubt they ever have problems either. The entire system can be bought in black at base prices or in ATACS, Multi-Cam, or Desert Digital camo for a little more.

My only beef with the system is that the magazine emptying button on the Adaptive Tactial magazines.

If you are a fan of the Mossberg 500, but you’ve wanted more rounds without having to thumb rounds in one at a time, the Sidewinder Venom is a really good investment in a gun that will never be worth less than you put into it. A lot of big box stores and gun dealers carry the kit at slightly discounted prices, and the mags are readily available right now in this slow market directly from the company and other places online. Converted Mossberg 500s and Maverick 88s show up on GunsAmerica from time to time as well. Check out the new forend on the Adaptive Tactical website before you jump on buying one. Maybe they’ll send me one and we’ll return to this product for a second round, and a second gun! I miss my FLEX forend, but oh well.

 

http://www.gunsamerica.com/blog/build-an-11-shot-mossberg-500-detachable-mags-no-gunsmith-required/