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Bullet Points: 5 AR Builder Upper Receiver Hurdles

It's easy for some of us to lose track of how many ARs we own. What's even worse is trying to remember every build we've ever completed or helped someone with. In all that time, though, we never had a problem slapping together an upper receiver — until we attempted to upgrade a DPMS LR-308. The lower may be simple on these guys, but upgrading the upper gave us fit after fit.

ARs chambered in 308 often bring their own unique issues to the table, especially if you have one made earlier than 2013. There are the Armalite versions that have almost no interchange, a few others claiming their own quirks, and then there's DPMS. Somehow DPMS made it to the King of the Hill slot and have (historically) been pretty much the standard for large numbers of us who roll our own.

We've had this DPMS LR-308 for a few years. It was a bare bones version we purchases assembled and ready to go from Brownells. This wasn't the Sportical that comes without an ejection port or forward assist and lacks the Oracle rail. We wanted to add a rail mostly to improve the looks, free float the barrel, and to protect the barrel from getting banged up.

So, how to go about it and what to spend?


Short answer is, we weren't concerned too much about weight or price, but when we had an opportunity to use a free (gifted) DPMS LR-308 rail, we were on it like a fat kid on a ham sandwich.

They made the rifle, what could go wrong. Right?

POF P308 - Vortex Flashider

1. Muzzle device

Our poor upper has had at least 4 different muzzle devices on it over the course of two years. This is likely just a hazard of life as a test rifle. Removing the factory installed flash hider is as simple as adding a wrench and turning it to the left. If you have a semi-permanent brake or flash hider mount for use with a silencer, it gets a bit more complicated.

The most important thing to remember is whether you used Rockset or Red Loctite. Each one has a separate method for removal.



Rockset involves sticking the muzzle device into a container of water overnight while it is still firmly attached to the barrel. Loctite involves the application of direct heat.

After remembering this muzzle device was attached with Loctite, we went through a tank of butane to generate enough heat for its removal. Once it came free we were ready to start our upgrades.

The biggest hurdle here was trying to remember what thread locking compound we used.

Don't be like us. Write that information down and try to keep it with the rifle. It'll save you some hours and anxiety.

2. Gas block


One of the complaints we often hear about the DPMS LR-308 is their use of an aluminum gas block. We've experienced no problems with ours, so we left it on until we decided to give it this makeover.

When we asked the folks at DPMS if what we had was considered a low-profile model for use with their rail, they assured us it was.

Well… Well, it wasn't.

This was a Picatinny railed block so you could add a front sight. We'd always run an EOTech on it, so it was of no concern to us until we decided to plus it up.

Taking it off was easy; we then went scouring the net looking alternatives. As it turns out, AR-15 and LR-308 gas blocks are interchangeable. We went with an Odin Works all steel low-profile model. We find adjustable blocks useless, particularly if going under a longer than normal rail.

Colt CRP20SS Adjustable Gas Block

3. Rail

We have a carbine length gas system, but did not want short hand guards. We were ensured that the DPMS SASS rail would fit with no problems at all, and so it seemed until we went to attach it.

Nobody told us it took a proprietary wrench. Thus we had no reliable way of installing it and torquing it with our multiple armorer's wrenches and hand guard tools.

Improvisation took over in the form of an expensive spanner wrench. Our only subsequent problem was the removal of the new gas block. It could not be turned because of the way the rail was spaced.

4. Gas block revisited

Once the rail was installed we figured, “No problem. We'll just just insert gas block and tube and tighten up the screws on the underside.”

Not so fast, Speed Racer. Apparently, the rifle-length rail has an access point in the bottom of the rail for a rifle length gas system. A 2 in. section of black aluminum stood between us and victory.

The rail came back off and we subsequently paid a visit to Reno Guns & Range to allow Tyler Narona to put it in his milling machine. He hogged out some space for us to attach the gas block, then covered up the bare aluminum with some Birchwood-Casey Aluminum Black and not it looks like it was manufactured thataway.

5. Sling Mount

When you decide to go with a rail system of almost any kind, you lose the ability to mount simple things like swivels and bipod studs without laying out money for another adapter. We went with a discrete SIG Sling Swivel that takes up exactly one rail slot.

This was one of the easier parts of the build and the only thing we may do next is upgrade to a magnified optic and a set of back-up iron sights.

What, pray tell, are the worst experiences you've had with a build?

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