View Full Version : Rainier Arms UltraMatch Billet Upper

29 March 2010, 10:20
Several months ago I got an RA UltraMatch Billet Upper. I used it in a midlength build as a general purpose carbine and test bed. This unit was a pre-production prototype, and has some differences from the current production run which has been improved.


Initial impressions:
I paired the RA upper with an LRB lower. Interface is excellent with no slop.
Rainier Arms produced this upper so that the center of the bore and the top rail are parallel. The front of the barrel mating face is also perpendicular, and the actual face is machined flat. Production models have a MilSpec anodizing treatment and are CNC machined out of solid billet 7075 aluminum. The production models also have the Rainier Arms markings, which were not present on my test unit.
The billet upper construction allows for the installation of free-float rail units that may require a slimmer profile than those found on some other billet uppers. When I selected the Daniel Defense Lite rail, the mounting collar fit like a glove with clearances built into the upper to fit the screws for the Lite rail.

Assembly and physical features:
I began with installing the forward assist. This was a little rough. This is not unusual in a new upper until the annodizing wears down and I've had many, many examples of the exact same thing with other standard uppers that I've assembled. I simply added CLP and popped the FA assembly repeatedly until it smoothed out. No problem now and function is fine. Smooth in and out with no hangs or roughness. The ejection port door went in with no problems.

View of the forward assist and ejection port.

The deflector is very angular, and the lines match the overall feel of the upper very well. While it may appear "jabby" it is not problematic in person. I have not had any discomfort from the deflector poking into my ribs, although admittedly I am not a lefty and do not run the carbine left-handed full time.

Detail of deflector configuration. Note scallop for rail collar screw just below top rail.

The build up on the exterior left side of the receiver common to billet uppers does not interfere with the bolt release or cause unintentional raising of the bolt latch. The upper is meant to work with a BAD or similar device. However, like any other modification or part it should be thoroughly tested by the end user before it is relied upon. I've used one without any issues.

Left side of the UltraMatch Billet Upper.

My version had M4 ramps, which very nicely mated with the M4 ramps on my BCM 16" middy barrel. Feed has been positive with no nose dives or setback rounds. Rainier offers the production upper with or without the M4 ramps.

Barrel and rail installation:
I mounted a Daniel Defense 12" Lite rail. In this area, I initially ran into a similar issue to the problem with the forward assist. I tried mounting the Lite rail barrel nut, and could get the nut started but then I would encounter resistence. More than I was comfortable with. I installed another Lite nut, and the same thing happened. I even tried a standard GI barrel nut, and it went on with no problem. I talked to John, and he said that it was probably an overly thick annodizing and to try it with a little more force. The technical guys at Daniel Defense agreed, so I tried more force.
It worked. I had to work the nut onto the rest of the threads, but once I did the annodizing wore down to the point that it got easier on subsequent mountings using the install and torque three times method of the -23. Using a heavy optic mounting base, I mated the rail to the upper to ensure the rails were in line with the upper and torqued the rail screws down. Once I made sure the rail was drawn tight, I removed the base. The rail is now almost touching the front edge of the upper, with the upper slots being properly spaced for 1913 spec mounts. There is no play between the upper, the barrel, and the rail.

The Daniel Defense Lite rail installed. Note fit between rail and upper and also the scalloped recesses for the collar screws.

Top Rail, sight, and optic mounting:
The top rail is without T numbers, which has been added to the production run. The rail is within spec and accepted a variety of optics, sights, and mounts. I've had an EOTech, an M68 in the Rail Grabber, an XTR with ADM Scout-X, ACOG with ADM mount, ACOG with Trijicon thumbnut mount, T1 with ADM mount, Badger Ordnance rings, and Leupold Mk4s. I've mounted Troy, Magpul, ARMS, Matech, and a CCH. No problems with any of these.

UltraMatch Billet Upper with ADM Recon mount and Magpul BUS.

In summation, I'm very pleased with this upper, although I do believe it will cost me a lower and another barrel. It will go very well with billet lowers if desired, and if you're one for looks it is certainly not lacking in that department. The angular lines of the upper blend very well with several billet lowers, and the aesthetics are great.
This was well executed.

The Rainier Arms UltraMatch Billet Upper is available from Rainier Arms:

29 March 2010, 16:03
A more recent configuration, using the VLTOR Modstock, Rainier Arms XTC, Magpul MIAD, Magpul AFG, and Aimpoint T1 with ADM mount.