This is what I've been wrecking myself trying to complete the past month:
Spare Barrel Scabbard: 1000d Multicam Cordura Exterior, 1" Murdock Jacquard Webbing, lined with charcoal grey Kevlar fabric for melt resistance, all seams exposed to scabbard inside are sewn with T70 Black spun Kevlar thread and T70 Tan499 Nomex on exterior, remaining bartacks and seams sewn with T70 thread. This one is sized for a Mk46, Mk48 or M240L short barrel.

Inside flap has black Kevlar pocket for ruptured cartridge or gas pistol cleaning tools:

Along the spine is a 1.5" webbing pocket for carrying an assembled cleaning rod for punching barrels fouled from blanks or punching stuck brass/cartridge in chamber. There is no female snap set into the flap yet because I haven't decided which cleaning rod to use since the Army issues mostly the Otis kits anymore. A WWII M1 Carbine M8 Cleaning Rod would fit perfectly.

You can carry the spare barrel fully secured with the main flap, or, you can remove the main flap and the four Fastex SRBs to use scabbard with barrel handle exposed for quicker access, retained by single 1" webbing strap with SRB. Velcro is there for a folded Velcro/webbing patch to hold the slot closed, and, for sticking to optional hook Velcro to be sewn/self adhesive to the inside flap if the enduser decides its necessary while under field testing in the moment:

Heavy Weapons Support Carrier, aka M192 Beavertail, 1000d exterior, 1" Murdock Jacquard Webbing, coyote 16oz hypalon-lined. Can be used to carry the M192 Tripod; 3ea 81mm tootsie tubes or M252 baseplate; 6ea 60mm tootsie tubes or M224 Baseplate; 2rd 84mm Carl Gustav RAAWS/Recoilless Rifle Carrier or M2/M3 Recoilless Rifle; or 5gal water can:


I made a Clothing Module, basically a 1000d/1" Murdock Jacquard Webbing MOLLE II Sustainment Pouch 2" taller to recup some of the carry capacity lost inside to the ammo can module:

We altered an issue Multicam Medium Ruck System with Downeast 1609 "U" Frame, I rebuilt the main compartment moving the #10 coil zipper along the front wall to give enough room on sidewall for a Helo Armament/M1026 7.62mm Feedchute and connectors. I replaced all the Tan499 1" PALS Loops with 1" Murdock Jacquard webbing because I wanted the ruck to look as close to factory as possible instead of mixed color webbing on the exposed panels. We moved the single flat and two vertical pockets from the back panel to sewn to the front MOLLE Panel, added 3 groups of 5 rows 1" Tan499 AA-55301 webbing to attach ammo can module with malice clips. The two exterior pockets I removed, sewed a PALS backing to, for use with Malice Clips as detachable GP Pouches, the former top one fits well under the M192 Tripod Feed and the larger bottom pouch fits on exterior of the beavertail if need be. I basically had just enough time to sew up the side seams and ammo can module before I had to go meet the enduser prior to movement. He's already made some recommendations to improve system.
Here's the altered Medium Ruck, the Heavy Weapons Support Carrier and clothing module:

