An MK 18-ISH Folder

The MK18 is as iconic as it gets when it comes to SBRs.

- Rob Curtis

THIS IS NOT AN MK18.

This is what we think the MK18’s punk-ass little half-brother would turn out like if its NSWC Crane papa stepped out and knocked up a young mistress. The MK18’s developmental roots go back to the 1960s and the original shorty AR, the Colt Commando.

NSWC Crane took inspiration from the Colt Commando when it made its CQBR drop-in upper receivers for U.S. Special Operations forces. These were 10.3-inch Colt-barreled uppers that eventually became the Mk18 when combined with surplus M16 rifle lowers from the Navy’s stocks. One of the most distinctive parts of the Mk18 is the flat dark earth RIS handguard. This was originally a Knight’s part, but Crane would later shift to a handguard made by Daniel Defense.

The Mk18 story gets confusing at this point because DD capitalized on the Mk18 name when it won the contract to produce the handguard. It wrapped its own parts in the MK18 handguard, christened it the “Mk18 Upper Receiver Group,” and made it available on the civilian market.

The DD MK18 upper, which is the basis of this issue’s Buildsheet rifle, is basically a DD’s recreation of the Colt produced Mk18.

We say basically because, though the DD handguard is an authentic SOPMOD (i.e. government-issued) part, the upper is an Mk18 in name only. DD used its own cold hammer forged 1:7 twist 10.3-inch barrel and upper receiver in place of the Colt parts found on the real deal.