MK18 Tuning Guide and Development
BY Herschel Smith
3 years, 4 months ago
This is a very well written and informative article. For those who are wondering, the M18 is the M-4/AR-15 variant with a typically shorter barrel, usually sporting a quad rail.
I see the need for this sort of weapon, given the focus on CQB in recent years combined with the fact that suppressors are now ubiquitous in the U.S. military, so a 10.5″ barrel isn’t really 10.5″.
But it does cause problems, including lug breakage, high pressures, etc. This article discusses some of the ways to mitigate those issues, including coated BCGs, adjustable gas blocks, and so on.
But just be sure to remember that when you go altering the design the engineer gave it, you introduce all sorts of unintended consequences. The machine will usually perform its best when unaltered from the original design, assuming the engineer is good.
And Eugene Stoner was good.
On July 21, 2021 at 7:28 am, Wes said:
Interesing article, thanks to the host. In the last/first department, Mr. Stoner was indeed good. There is something in this about history not repeating but rhyming. Looking back at the first CAR-15’s with a 10″ barrel, and later discovering that 11.5″ was much more simpatico to component life. The Mk.18 has been a great tool but now we find that a URGI (Upper Receiver Group Improved) version of an 11.5″ is being fielded (or will be shortly).
A few of the real big boys (e.g., DD) do their Mk.18 with a properly sized gas port, and it is less than the typical homemade ‘clone’ whose barrels are overgassed to accomodate sub-spec ammo. (Many of the latter are probably in the hands of people who’ve configured them as pistols.) The producers for .Mil and serious civilian Mk.18 system users are making an assumption about regular use with a suppressor. These fielding programs also typically include an improved charging handle to mitigate gas to the face.
A properly sized gas port (.070 if recalling correctly vs. the oft-seen .076 or even .0785) will mitigate much of the wear issue. In the FWIW Dep’t, a seriously experienced armorer to the SF downrange advises that there are now just 3 buffer systems in the inventory. The full-length rifle buffer, an H2 (1 regular, 2 tungsten weights) using a standard carbine spring, and a hybrid for some seldom-used variant.
They do make a handy travelling companion set up correctly.
On July 21, 2021 at 5:48 pm, xtphreak said:
over engineering usually costs more but provides a better margin of safety.