A projectile weapon
An MK-33 was a projectile weapon used on Earth in the 21st century.
The original colonists of the Terra Nova colony had weapons resembling MK-33s when they departed Earth in 2069 to establish the colony. In 2151, the descendants of the colony were still using the weapons – Athan used one, but Lieutenant Malcolm Reed wasn't sure if it was an older model MK-33 or an MK-34. (ENT: "Terra Nova")
In unused dialogue from the script of "Terra Nova", Reed (moments before leaving the Novans) advised Athan to check the firing mechanism of his weapon, having noticed it was rusted, an observation Athan immediately confirmed for himself, upon inspecting the weapon.
The weapon prop was reused in ENT: "Shadows of P'Jem" to represent a Coridanite weapon and was sold off at the It's A Wrap! sale and auction on eBay. [1](X) The weapon was a modified replica MP5 submachine gun without the magazine and modified with a chrome metal barrel. The weapon was inscribed "Made in Germany."
The call sheets of the episode are simply listing "auto-rifles" in the props requirement section.