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Rainier Arms, LLC

Rainier Arms UltraMatch Billet Upper & Ambi Lower Combo Set .308 Mod 3

Rainier Arms UltraMatch Billet Upper & Ambi Lower Combo Set .308 Mod 3
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Our billet sets are CNC machined from solid billet 7075-T6 aluminum which is 70% stronger than the commonly used 6061 aluminum and finished with milspec hardcoat anodize to a surface hardness of 60 Rockwell. We have designed our lowers with an ambidextrous bolt release with extended latch for smoother deployment. The precision machining on our billets are well known in the industry and we are excited to introduce our combo sets for your next .308 rifle build.


  • Ambidextrous Extended Bolt Release
  • 7075 Billet Aluminum
  • Type III Hard Coat Anodized
  • Flared Magwell
  • Integrated Trigger Guard
  • Tensioning Screw for proper Upper/Lower Fit
  • Bolt Catch Assembly Screw (No Roll Pin to install)
  • Uses Standard DPMS Type .308 lower parts kit
  • Upper receiver is compatible with DPMS High profile 308 Handguards
  • Weight: 28oz


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Additional Info

Additional Info

SKU RA:Set:308 Billet UM Upper/Lower Mod 3
Manufacturer Rainier Arms, LLC
Finish No
Barrel Length No
Caliber No
Configuration No
Option No
Gas Length No
Height No
Rail Length No
Mount No
Profile No
Reticle No
Co Witness No
Size No


Customer Reviews (10)

No commentReview by Steven
- (Posted on 11/18/2016)
Good but not greatReview by Larry
Nice overall. The receiver tensioning screw nice feature but if the receivers were a bit better mated you wouldn't need it. As is, with the tension applied you can see there is amount of gap between the upper and lower that you would expect from non billet sets, but not a matched billet set. Also the area cut out for the mag catch bar is not quite deep enough. I tried three different mag catch bars (different brands) and they would barely hold the mag enough to keep it from dropping out if you wiggle the mag. I ended up working on one of the bars so it would catch the mag a bit better. All parts I used was dpms or dpms designed parts. Last issue was the left side ambidextrous mag release button that comes with the set preloaded the mag release lever and with it installed the mags would just fall out. I filed the curved actuator tip down until it no longer preloaded the release bar. So with a little filing on the ambidextrous mag release, and trying several mag catch bars and working on the best one, everything fits and works now.
One other note. Putting enough tension on the receiver with the tensioning screw to take the wiggle out makes it damn hard to pull the receiver takedown pin out. So don't over tighten it. Or you will constantly be removing the grip to readjust.
I like the receiver overall but since I had a few issues which I have never had with any of my other builds this set only rates four stars. (Posted on 11/17/2016)
No commentReview by Sean
Fit and finish is excellent. The ambi bolt catch and mag release is the way to go and makes this set worth the money. The upper was missing the bolt catch set screw. I contacted them and they mailed it right to me. Great service.

The set screw for the rear take down is not a great design and I drilled a small shallow hole in the grip to retain the spring. It is incredibly hard to depress that spring and install that tiny set screw. (Posted on 11/17/2016)
No commentReview by Hector
Very, very impressed with the quality and lightness of this set. Wow! (Posted on 11/6/2016)
No commentReview by Jason
Love the fit/finish AND all the built in ambi features!!!! JAWS ARMS will definitely be using these in the future!!! (Posted on 11/4/2016)
Good with defectsReview by Justin
It is a very well made upper and lower. Everything went together smoothly except the rear take down pin. Actually it wasn't the pin, it was the spring that that holds the pin in. The springs that comes with the DPMS lower kit is to long and had to cut a little off to made it work. I still highly recommend this combo kit to anyone. (Posted on 10/22/2016)
Good with some defectsReview by Lincoln Meissner
The tolerances are phenomenal and this is a very well machined piece of metal. That being said, the detent for the rear takedown pin is too big to fit in the threaded hole. I don't know if this is from the threads or the hole is too small, but the detent I have is now stuck. The front detent hole is perfect and I had no problems installing.

Secondly, the rod for the ejection port cover is too long and prevents the barrel nut from screwing down flush. It had to be trimmed.

If they notated that a smaller rear takedown detent would have been required, and trimming would be required on the ejection port cover rod it would have been a higher rating. (Posted on 7/22/2016)
No commentReview by Michael
This is a great looking lower/upper receiver! Tremendous and beautiful craftsmanship. Having that said it was a pain to install the lower parts. Installing the mag catch was a bit tricky with the detail of the lower but nothing more difficult like installing the rear take down pin. It was very difficult, I lost 2 springs and when I finally got the screw to go in and screwed all the way down the take down pin wouldn't move if my life depended on it. I had to trim down the spring for it to fit with the set screw installed (Called Rainier Arms for this). Honestly I think the take down/pivot pins should come included with the lower/upper due to this difficulty like the Mega Maten does. Once I was done though, it looks great!! I am probably not going to build another AR-10 but if I was I would get another one! (Posted on 7/5/2016)
No commentReview by Walter
Match made from heaven (Posted on 6/6/2016)
Fantastic base for your heavy metal gunReview by Jason
Built a 3 gun 308 with this and the fit was perfect. The tolerances are spot on and it has functioned flawlessly with no special fitting required. In the AR308 market it is always more difficult to find parts you can fully expect to fit and function the first time, this set is a part you can count on.

One note - the dust cover door is not included as shown in picture (not a big deal) (Posted on 6/29/2015)

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