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Tandemkross

Author Topic: Palmetto State Armory AR-9 Glock Magazine Lower and Hybrid Upper  (Read 7511 times)

Offline GunLink

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Palmetto State Armory AR-9 Glock Magazine Lower and Hybrid Upper
The GunLink AR9 9mm AR



Decisions, 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 Lower



We 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. 


« Last Edit: January 28, 2017, 03:57:29 PM by GunLink »

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Offline GunLink

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Re: Palmetto State Armory AR-9 Glock Magazine Lower and Hybrid Upper
« Reply #1 on: June 23, 2016, 10:27:21 PM »
The Upper

The upper arrived about a week or two after the lower did, thanks to spotty availability on the PSA website.  At one point, I had one in the cart at the same time as the lower, but it disappeared when I tried to complete the order and then they were magically out of stock.  I spoke with a PSA rep at NRAAM and he explained why this happens using a bunch of words, but what I heard was basically that their order system is old and it sucks.



When uppers did come into stock, they were of the 7.5" variety with KeyMod rails, so I got one in the cart and got it ordered.  We are not necessarily big KeyMod fans around here, but c'est la vie - we had already waited almost a week after receiving the lower before one even came in stock.  Then, in typical PSA fashion (this happens almost every time), almost immediately the M-LOK version of the upper became available.  Not only was it in stock now, but it was also cheaper and included free shipping.  Every.  Single.  Time. 

Since I had just placed the order, I called to see if they could either price-match the new deal or modify the order to the M-LOK upper that I preferred (even if I paid the now-higher price difference) and was told that I was out of luck - nothing they could (or would do). 

As with the lower, the upper came complete - assembled and including the bolt and charging handle.  Unlike a standard AR15, the 9mm AR is a blowback operated ordeal instead of using a gas impingement system.  Also different is the fact that, instead of a bolt carrier that houses the rotating bolt, the entire thing reciprocating inside of the upper receiver is the bolt itself.  The 9mm AR bolt is essentially a BCG with a 9mm bolt face machined into the front of it and a weight (necessary to slow the bolt's movement during blowback operation) attached to the rear.

Because of the differences in the feed, extraction, and ejection systems between SMG magazines and Glock magazines, a different bolt is typically used for each type of build.  The upper that I ordered included PSA's "Hybrid" G-9 bolt which will allegedly work with either type of lower.



A concern that I had when ordering the upper and bolt sight-unseen (the photos on the PSA website are not particularly detailed) was whether or not the bolt was "ramped."  The way that a BCG or, in this case, the bolt itself interfaces with the hammer is that when the bolt moves rearward, the shelf that surrounds the back of the firing pin hits and drags across the hammer, causing it to pivot around the hammer pin until it resets and catches on the disconnector.  If you look at the underside of a standard AR15 bolt, you will see a nice, friendly angle that begins contact higher up (further from the hammer pin) and allows it to be pushed back and downward relatively gently. 

Some 9mm bolts do not have such a ramp.  This means that when the the flat shelf of the bolt slams directly into the hammer, the two surfaces are near parallel and the point of impact is much closer to the hammer pivot pin.  Because of this, the energy that is transferred from the moving bolt to the hammer is much lower, more violent, and more rearward than downward compared to a ramped bolt.  Although we have not experienced such damage, we have seen anecdotal reports of this causing the hammer pin hole in the lower to become oval.  This might not be an issue if you are using a replaceable $40 lower on a standard rifle or pistol, but if you are going to pay a premium for the dedicated lower and then pay another $200 to register this particular lower as an NFA item, it becomes a bit more of a concern. 

When we ordered, we were not sure what we would be getting as far as bolt ramping goes.  There is some history of PSA having confusion on whether 9mm AR bolts ordered from them would be shipped in ramped or un-ramped configuration.  There are reports of people ordering one but receiving the other.  For a while, PSA loudly claimed that only bolts marked as ramped on the website would be ramped but purchasers were reporting that all bolts, regardless of whether they were marked as ramped, came with a ramp.  The complete upper we ordered had no mention of a ramp...

It all turned out to be much ado about nothing, however, as the upper arrived with a ramped bolt, even if it did have some ugly machining marks on it.



The only other downside of the upper that we could find was the fact that the barrel came with 1/2-36 threads instead of 1/2-28.  What PSA claims this means for them is that some idiot couldn't inadvertently screw a 5.56 muzzle device onto the barrel barrel and get all explodey like when Bugs Bunny sticks his finger in the end of Elmer Fudd's barrel.  What it means for Team GunLink is that we can't use a 9mm suppressor on it without having to buy another expensive adapter.  Thanks, PSA.  You know... other manufacturers sell 9mm AR uppers and barrels with 1/2-28 threads and everything seems to be working out fine. 

« Last Edit: January 28, 2017, 03:56:12 PM by GunLink »

Offline GunLink

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Re: Palmetto State Armory AR-9 Glock Magazine Lower and Hybrid Upper
« Reply #2 on: January 28, 2017, 03:57:46 PM »
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