I mentioned in the intro paragraph that most people today will take a semi auto rifle over a shotgun. There are good reasons for this, but not enough to write off the shotgun for everyone.
First is the issue of recoil on a typical 12 gauge shotgun. Semi auto shotguns will typically sport less recoil than aa pump action due to them utilizing a lot of the gas to cycle the action. That said, the recoil even on low/target loads is going to be much higher than the recoil on an AR15 style rifle. For this reason, most women and some men will find themselves challenged to control the shotgun, making it less than a universal weapon for all to use and enjoy. For some people, shooting 1000 rounds out of their favorite rifle can be fun, but tiring. In my experience, it only takes about 100 shells of high brass 00 buck or slugs to be tiring if you don’t shoot shotguns very often. This means the shotgun operator needs to be familiar with the shooting characteristics of the shotgun in order to stave off fatigue when using the shotgun during a long engagement.
Second issue that people have with the shotgun is the range limitation. Even when using slugs, you are really going to find yourself challenged to keep the shotgun accurate at ranges past 75 yards. For this reason, if you want the power it offers, you will almost always have to be close to your target. But the same thing goes for a pistol, and people seem to think that is just fine despite how much work it takes to get really good with a pistol…HMMMM
Last issue is that the shotgun is typically slow to load, but also needs frequent loading. 99% of the shotguns out there will have a capacity less than 10 unless they are magazine fed with a cumbersome drum or a freakishly long novelty magazine. You will have to practice reloads often because there is almost a guarantee that you will have to feed the beast during a fight. Most semi auto rifles today feed from a 30 round mag which will last longer and is easy to reload in seconds. To reload a shotgun fast, you will need to drill loading a few shells at a time from all types of positions. Handling loose shells in a fight demands a steady hand with good coordination and speed which can only be achieved through routine practice and testing under time. This is a basic necessity for any shotgun operator.
The shotgun has been used to take down game of all types for hundreds of years. From duck to Grizzly, the shotgun has helped people feed their families. A simple #8 target load can not only be useful for clay shooting, but also as a less lethal option, as well as a method of damaging/destroying surveillance drones in midflight. Ideally, the high brass loads used for taking down a duck or turkey would be more preferable for taking out a drone, #8 shot can be used in a pinch at close range.
Where the shotgun really separates itself from a semi auto rifle is in close quarters combat. It is not new knowledge that a load of 00/000 Buck and a 1oz slug are absolutely devastating. Even at ranges out to 50 to 75 yards, these loads can inflict real damage on your target. The tradeoff is obviously going to be that these loads are going to have much more recoil. However, a CNS hit from a single slug or 00 buck load will do enough damage to take someone out of the fight. In comparison, there have been many cases of people requiring more than 5, 6, 10 rounds from 5.56 NATO to be out of the fight. Typically, this is because of how the projectile passes through the body and what it hits while going through. For 00 buck, 000 buck, or 1oz slug there is going to be such a large area that is permanently destroyed by the projectile(s) that it CAN be roughly equal to the effects of a rifle shooting someone 6-8 times.
I am not trying to say that the shotgun is the king of all warfare. But what I am saying is that any close quarters engagement that a partisan group may take part in should have people carrying a shotgun. It is highly effective and serves multiple purposes. Get a few highly skilled shotgun operators in a squad and they will no doubt be a force multiplier for your force. Just think about it.