Editing Shotgun slug (section)

===Wad slugs===
{{Unreferenced section|date=January 2021}}
[[Image:Plumbata shotgun slugs.JPG|thumb|right|250px|From the left, plumbata discarding sabot (No. 1); plumbata slugs (No. 2, No. 5); wad slug (No. 3), sabot slugs (No. 3, No. 4)]]
A modern variant between the Foster slug and the sabot slug is the wad slug. This is a type of shotgun slug designed to be fired through a smoothbore shotgun barrel. Like the traditional Foster slug, a deep hollow is located in the rear of this slug, which serves to retain the center of mass near the front tip of the slug much like the Foster slug. However, unlike the Foster slug, a wad slug additionally has a key or web wall molded across the deep hollow, spanning the hollow, which serves to increase the structural integrity of the slug while also reducing the amount of expansion of the slug when fired, reducing the stress on the shot wad in which it rides down a barrel. Also, unlike Foster slugs that have thin fins on the outside of the slug, much like those on the Brenneke, the wad slug is shaped with an [[ogive]] or bullet shape, with a smooth outer surface. The wad slug is loaded using a standard shotshell wad, which acts like a sabot. The diameter of the wad slug is slightly less than the nominal bore diameter, being around {{convert|0.690|in|mm|abbr=on}} for a 12-gauge wad slug, and a wad slug is generally cast solely from pure lead, necessary for increasing safety if the slug is ever fired through a choked shotgun. Common 12 gauge slug masses are {{frac|7|8}} oz (({{convert|383|gr|g|abbr=on}}), 1 oz (({{convert|437.5|gr|g|abbr=on}}), and {{frac|1|1|8}} oz (({{convert|492|gr|g|abbr=on}}), the same as common birdshot payloads. Depending on the specific stack-up, a card wad is also sometimes located between the slug and the shotshell wad, depending largely on which hull is specified, with the primary intended purpose of improving fold crimps on the loaded wad slug shell that serves to regulate fired shotshell pressures and improve accuracy.

It is also possible to fire a wad slug through rifled slug barrels, and, unlike with the Foster slug where lead fouling is often a problem, a wad slug typically causes no significant leading, being nested inside a traditional shotshell wad functioning as a sabot as it travels down the shotgun barrel.

Accuracy of wad slugs falls off quickly at ranges beyond {{convert|75|yd|m|abbr=on}}, thereby largely equaling the ranges possible with Foster slugs, while still not reaching the ranges possible with traditional sabot slugs using thicker-walled sabots.

Unlike the Foster slug which is traditionally roll-crimped, the wad slug is fold-crimped. Because of this important difference, and because it uses standard shotshell wads, a wad slug can easily be reloaded using any standard modern shotshell reloading press without requiring specialized roll-crimp tools.