Mossberg’s Shockwave is immensely popular. There are waiting lists to buy one. Well Adaptive Tactical will be making a Sidewider kit for the Shockwave.
I will be honest, I have used a Sidewinder kit on my Mossberg 500 Roadblocker. I found it added a lot more weight than I would have liked since most of it is forward of the ejection port. It felt unwieldly and the magazine system was finicky. However, handling the Shockwave with the new Sidewinder kit, felt perfect. If you hold the Shockwave at waist level then the weight is much more manageable and you can have a 10 rd drum or box magazine to feed the Shockwave.
The new Shockwave Sidewinder kits will retail for $269 and come with a 10rd drum. Adaptive Tactical is looking to have these released in the Summer. The representative also mentioned that they are looking into modifying Remington 870s in house and offering them as complete guns. The problem is that the 870 mag tube is not easily removable for most people.