DPMS A2 Upper Receiver

A lot has changed at DPMS since they were merged with Remington Arms and Bushmaster. Luckily quality has remained above average, and they are still carrying a few odd components that are hard to find. On the short list are the HBAR A2 gas blocks and upper receivers. While a large percentage of people consider the A2 to be a throw back relic that should be completely replaced by the flat top receivers, it does have its place. In the case of the .50 Beowulf, the A2 is an excellent platform. Not only does the carry handle handle provide stiffness, but it also hosts robust iron sights.


DPMS A2 upper
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While I am a huge fan of the ACOG/EOTech sights, I do not see a real point on a weapon that is ballisticly limited to a few hundred meters at best. At ranges under 75 meters, I find myself just as quick with iron sights as with holographic sights. 75-150 meters the differences become apparent. For this review we are going to assume you have your reasons for the A2 architecture. To avoid further debate lets just assume you are building a zombie gun.


A2 Teflon coated upper
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One of my favorite features of DPMS is that they teflon treat their receivers. While this is some what common on billet receivers, it is a hard to find option on an A2. Another nice feature is the 7075 alunmium. 7075 makes for a nice solid platform. In some cases I lean towards 6061 for the upper just to save wear and tear on the lower,in the case of a big bore AR I favor stiffness.


Ejection posrt opened up
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If you are going the big bore route, you will need to open up the injection port. Most sources seem to prefer a 16mm wide port. From my experience and research anything wider than 15mm should provide reliability. The key when opening up the injection port is not to cut too much off the top. If you remove too much material from the top, you will not have a functioning dust cover, and you will also weaken the bearing surface of the bolt


Prepped for duracoat
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People tend to shy away from the custom route with these calibers due to the need to refinish the milled area after opening the ejection port. While you need to exercise care, this is not a show stopper. You can use anything from an end-mill to sand paper to get the job done. The real trick is in the refinish. The best solution I have found is Durabake by Duracoat.After milling, just mask off the surface, clean with some degreaser, heat the part to ~150F and paint. 15 minutes after painting the part needs to be placed in an oven at 350F for ~20 minutes. Because we are dealing with aluminum, I strongly urge you to slowly cool the part after curing the paint. Turn the oven off and wait is the best course of action.


finished
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After just one coat you can hardly tell any work was ever done. Some people comment that the Durabake has an almost ashy appearance. If you get that effect you need to apply a second coat. A second coat is better than trying to do a single heavy coat. Years on the internet and I know all about the "10 foot rule". Thats why I have included high resolution photos of this job for you to get a better idea the actual results.