Sub 6 with a Twist

I recently added the Scalarworks LDM to my lightest carbine which shed 1.5 ounces from the total weight, lowering it to 6.13 pounds (unloaded). I stood there looking at the scale for moment and realized that I was so tantalizingly close to the 6 pound mark, that I would have to go for it. There are certainly AR-15 builds that are lighter than this but this one is different. It has a bit of a twist that sets it apart from most. I have a set of requirements that I will not compromise in order to maintain this carbine’s intended use as a defensive firearm and the idea for this project was to start with base components that I already owned to show what could be done with careful retrofitting versus building something from the ground up.

Throughout the project, these requirements have guided my decisions:

• It must have an optic, light, back up sights, and a forward grip of some kind (hand stop, vertical grip, etc.). This alone sets it apart from many lightweight builds which are generally done with just an optic or just irons and no light in order to save weight.
• It must be able to accept a two point sling.
• It must have a rail that completely covers the gas block (11″ or greater since this is a midlength). This is to support the way I shoot, support practical field shooting positions, and make barricade shooting easier.
• It must have an appropriate weight buffer (an H buffer in this case) and an M16 bolt carrier group. I do not want to get into adjustable gas systems and lightweight recoil parts.
• It should have a forward assist… not because I use it often but because I like the idea of it and I have a hard time giving it up.
• I will not resort to drilling holes in grips, stocks, or similar lightening methods.

Those requirements, coupled with the limitations of using an upper I already had, make this an interesting and challenging project. I could purchase a BCM upper with their KMR and excellent ELW profile barrel and be done but that strays outside my idea for working with what I already had (a BCM 14.5″ lightweight midlength with pinned A2X). I could add a low mass carrier and adjustable gas block and done but that goes against my requirements. So, that basically leaves me hunting and pecking for lighter weight options.

The carbine currently weighs 6.13 pounds which means I will have to find a way to shed a hair over 2 ounces. My current plan is go with a rail system that is lighter than my current Fortis REV. I will probably go with the Fortis REV II since it is about 1.4 ounces lighter than my current REV and uses the standard barrel nut as an attachment point which is important since I have a pinned muzzle device. I will also try to track down the lightest Keymod forward grip I can find. Those two items alone might take me to the sub 6 promised land.

Hopefully, this will serve as some inspiration for what can be done to reduce the weight of the carbine that you already own.
Here is a breakdown of the carbine as it stands:

• BCM 14.5″ midlength upper with lightweight barrel profile – It has a pinned A2X and the original FSB was shaved to fit under a hand guard.
• LMT M16 BCG
• Aimpoint T1 in Scalarworks LDM
• BCM GUNFIGHTER Charging Handle MOD4 (medium latch)
• Fortis REV Rail 12″
• Rosch Works SL1 Sight Light – This is one of the most important parts of the build. It combines a top quality weapon light and front sight that weighs less than most weapon lights alone.
• Magpul MBUS Gen 2 Rear Sight
• Impact Weapons Components Weapon Control MOUNT-N-SLOT (use code triggerjerk to save 5%)
• V7 Weapon Systems Lightweight Dust Cover and Forward Assist
• GWACS Armormy CAV-15 Lower given the full treatment by Echo Nine Three – These lowers are bull strong and very light, especially after they are worked over by Echo Nine Three.
• Standard lower parts and fire control group

You can find many of the parts listed above at Brownells. I purchase a lot of my parts there because of the trust they have built with me over the years.