Shotguns are cool. Slugs are cool too. RIO Ammunition decided that regular old slugs were not
cool enough—so they gave us their line of Royal MG slugs that deal massive damage.
Rio classifies their Armored MG style slugs as big game rounds. I can’t imagine too many large
animals that could stand up to a well placed shot with one of these heavy projectiles. The load
weighs 1.125 ounces and travels at an astonishing 1,540 feet per second. That equates to nearly
2,625-foot pounds of kinetic energy out of that old 12-gauge shotgun. To put that in perspective,
a baseball travelling at just over 500 miles per hour would hit you with roughly the same amount
of energy as this slug.
Unfortunately, for your target, the RIO
designed the lead portion of the slug to
fragment upon impact, dumping all the
energy into the target directly, creating
massive trauma. Running through the
middle of that lead slug is a steel rod
with a pointed tip, which can poke holes
in barriers or thick animal hide. When
firing, we noticed that these were not
exactly low-recoil shells. The massive
amount of powder tightly packed in the
shell helps provide substantial recoil on
our lightweight tactical shotgun. To my
delight, our aluminum framed Mossberg
stood up to the task without any
This slug bears a striking resemblance
to a Brenneke style slug. If you are
unfamiliar with Brenneke style slugs,
here is a refresher. A German gun and ammunition designer named Wilhelm Brenneke
developed the Brenneke style slug in 1898. The original Brenneke slug is a solid lead slug with
fins cast onto the outside, much like a rifled Foster slug. In the case of the Rio, the steel air rod
adds greater penetration, while the lead projectile fragments. Originally, there was a plastic or
felt fiber wad attached to the base that remained attached after firing. This wad serves both as a
gas seal and as a form of drag stabilization, much like the mass-forward design of the Foster
slug. The fins, which Brenneke designed in the projectile, impart little or no spin to the slug. The
actual purpose of the fins is to decrease the bearing surface of the slug to the barrel and therefore
reduce friction and increase velocity.
Unlike most Brenneke type slugs, RIO designed this particular slug to fragment considerably on
impact, making it extremely deadly. The sharp shoulder and flat front of the Brenneke is similar
in dimensions to a wadcutter bullet. This means that its external ballistics restrict it to short range
use, as its accuracy is similar to that of an American Foster slugs while retaining the improved
penetration and slug integrity of the Brenneke design.
This particular design seems to work as a multi-purpose slug round. Since the Rio MG can
penetrate barriers while still causing lethal damage, this slug is equally adept to both hunting and
law enforcement applications. In this role, shooting through barriers may be a necessity.
Changing out shotgun rounds in the middle of a gunfight with a perpetrator could get you into
serious trouble. As a law enforcement or large game hunting shell, the Rio MG slug will get the
job done, no questions asked.