Palmetto State Armory AR-9 Glock Magazine Lower and Hybrid UpperThe GunLink AR9 9mm ARDecisions, decisions. What should we build?With the
ATF ruling 41F looming near, the time was right to move on the 9mm SBR project that Team GunLink had been putting off for too long. The pistol caliber carbines already in the GunLink stable are a real blast to shoot: light recoil, affordable and plentiful ammo, accurate to reasonable distances, and great for punching holes in paper, ringing steel, or dispatching varmints. However, they aren't very short or maneuverable to begin with and, if you add a suppressor into the mix, they move into the realm of
unwieldy.
The decision of which platform should be used as the base was a bit of a struggle. Using a handful of criteria we narrowed it down to a few with the AR platform eventually winning out. With price as a contributing factor, that field was narrowed down further. In the 9mm AR world there a number of options to choose from. The first is whether to use a standard AR-15 pattern lower with a magazine block (basically an adapter that fills out the unused part of the mag well to fit the smaller 9mm magazines) or a dedicated lower that is purpose built to natively accommodate 9mm magazines. Dedicated lowers tend to cost more than standard AR lowers, but quality magazine blocks cost can run on the expensive side so, even with the abundance of affordable AR lowers on the market these days, the cost is a push. Since the plan is for this lower to only ever be a pistol-caliber firearm, we decided to go with a dedicated lower build.
The next decision was what kind of magazine the new project would be fed from. The two main choices here are SMG magazines or Glock magazines. Provided that you use the right ones, SMG magazines have a reputation of reliability and are generally available at a reasonable price. These types of magazines - essentially an Uzi magazine modified for the AR's magazine and bolt catches - are what the
Colt 9mm SMG, as well as many of rifles patterned after it, use. However, Glock magazines are also known for their reliability and availability and, since most of the team owns or shoots some kind of glock pistol, there is no shortage of magazines around. Not wanting to have to stock up on yet another type of magazine, the decision was made that the new project would incorporate a dedicated Glock-magazine lower. As a relatively new build type, this narrowed the manufacturer down to only a couple, some of whom - as best as we can tell - use the same lower with a different roll mark. The price and availability race was won by
Palmetto State Armory (PSA), we ordered one, along with the matched upper and it was on its way to us before long. (
Really - it didn't take long at all. Things really seem to have turned around at PSA)
It has arrived!Ok, so technically, the lower and upper were not both in stock at the same time, so they came about a week or two apart from each other, with the lower arriving first. That's OK, it gives us a chance to check it out, inspect it, get anxious for the upper to come, etc.
The LowerWe mentioned the two styles of 9mm AR lowers above: the dedicated type that we used, and a standard receiver with a magazine block. In the latter type, the magazine block incorporates the ejector, feed ramp and, often, the bolt catch to enable the last-round bolt hold-open feature (LRBHO). On dedicated lowers, these features, when present, are incorporated directly into the receiver. In this case, the PSA Glock lowers feature an ejector, but no option for LRBHO and, to our chagrin, no feed ramp.
By their nature, the LRBHO on a 9mm AR is a somewhat tricky beast. On a standard AR15, the magazine is situated such that it extends all the way to the rearmost wall of the magazine well. This allows the follower to lift the bolt catch after the last round has been stripped off and fed into the chamber. Because 9mm magazines sit further forward (due to the adapter on standard lowers or by design on dedicated lowers), the follower is out of reach of the stubby bolt catch of a standard AR. There are a number of ways around this such as using a bolt catch with a longer "finger" that will reach the follower or incorporating a lever into the lower or adapter that will either act as a bolt catch itself or lift the stock bolt catch. The PSA Glock lower, however, features neither of these workarounds and simply does not feature a LRBHO.
I suppose it is not the end of the world if you have to have to work the charging handle to reload if you lost count of rounds fired before running dry. The bolt catch still works manually and the bolt release feature operates normally.
Note the void between the bolt catch and the rear wall of the magazine well.Of greater concern than the lack of LRBHO on the lower is the less-than-perfect machining job on the ejector and, of even more concern out of the box, the lack of a feed ramp. As can be seen in the photo above, a small raised ridge is present about halfway up the angled rear edge of the ejector and, in the previous photo, there are drag marks from the bolt riding along the side of it. I will be contacting PSA to ask if this is the normal condition of the ejector machining and ejector/bolt mating. Without a feed ramp, rounds fed from the magazine have to make a not-inconsequential leap through space of about half an inch before (hopefully) making their way into the chamber. More later on whether or not either of these things cause reliability issues.
Aside from those minor lack of features and finish work on the parts kit, the lower itself seems to be well made. The integral trigger guard has ample room to get even gloved fingers in and out easily and the magazine release button (or, more accurately, lever) is large and looks sturdy. The forging and machining look well executed and the roll marks are clean and, subjectively, not distasteful, albeit large. The rest of the parts appear to be standard run of the mill LPK fare.
One nice feature that I appreciated and hadn't seen on an AR lower before is the presence of set screws in detent spring holes - a feature that I discovered when I unscrewed the pistol buffer tube and, without thinking, removed the receiver end plate only to discover that the spring and detent hadn't shot across the shop.
While on the topic of the end plate and pistol buffer tube, both were included with the complete lower that I ordered from PSA. The buffer tube is pretty standard fare; fluted metal with no padding, shoulders, or any other distinguishing features. The end plate was, however, an incremental upgrade over one that might be grabbed at random out of the parts bin, featuring ambidextrous sling mounts (for hook-type slings) on both sides.