August 17, 2012
Gus Norcross, originally trained on National Match rifles and pistols by the National Guard Marksmanship Training Unit specializes in Garands, M14s and 1911s at his small shop on the coast of Maine. His website is www.angusarms.com. He will be offering gunsmithing tips and tricks on Fridays.
The next evolutionary change in the way we buy AR type rifles may be the monolithic upper. These one-piece upper receivers seem more expensive at first glance but let us consider the assembly steps needed to complete a conventional upper with free float fore-end. We would install the barrel and barrel nut and torque, it being careful to align one of the holes with the hole in the face of the upper receiver so the gas tube will pass dead center through it.
Now we install the jam nut. Then install the handguard onto the barrel nut. Tighten the jam nut against the fore-end, being careful to keep the top rail dead level with the rail on the upper receiver. Sometimes, several attempts are required to achieve perfect alignment.
Now consider the assembly of a monolithic upper like the unit from Mega Arms in the photos. We insert the barrel and supplied castle nut into the upper and torque it. Done. Alignment of the barrel nut is unnecessary. The top rail is one piece.
Now picture an assembly line where hundreds of uppers are being assembled. How many monolithics could you assemble in the time it takes to complete a conventional upper? Three, four, five? Time is money in a production shop. Reduced assembly time may result in the monolithic rifle becoming cost competitive with conventional designs.
One piece uppers are slightly heavier (ounces) but more rigid and offer a smaller diameter forend. Manufacturers such as Colt, LMT and Armalite have been marketing monolithics for some time. Conversion kits are available for carbine, mid-length and rifle length gas systems.
Are monolithic uppers destined to become the next standard? Flat-top upper receivers replaced carry handle models over the last 10-12 years. Ten years from now we may purchase a new factory rifle with a one piece upper as standard equipment and consider the multi-piece uppers of the last decade obsolete.
The Mega Arms monolithic upper kit
The Mega Arms monolithic upper kit contains the upper, a barrel castle nut, a wrench to tighten the barrel nut and one short rail section.
This LMT carbine was updated to monolithic configuration with a Mega Arms kit. It's stiffer and makes it easy to mount any sort of optical sight.