Umarex Glock 17 Gen4 Part 2

Umarex Glock 17 Gen4 Part 2

Choosing between a Third Gen G17 or Gen4

By Dennis Adler

Keeping pace with changes in Glock design between the Third Gen and the Gen4 (right) you can see that the muzzle has changed slightly (also the recessed .177 caliber barrel is not blacked out like on the Third Gen model), the contours of the frame and front of the slide are different, as is the design and size of the recoil spring and guide rod front plug protruding from the front of the frame.

This is an easier decision within the centerfire pistol world based on price vs. features; the Third Gen Glock 17 (now referred to as the Original) is the basic Glock model and priced at $499 vs. the more feature laden and easier to handle Gen4, priced at $599. You are stepping up between models to an improved recoil system and grip design, and the addition of interchangeable backstraps for the difference in price. With the new Umarex Glock 17 CO2 models, the price differential is much less, about $30, and the difference in features weigh more heavily with air gunners then individuals choosing between two 9x19mm Glock 17 versions. In a lot of ways, the price differential is commensurate, upgrades between centerfire pistols are commonly $100 or more, and those choosing the older model are often making a financial decision, and Glock wisely keeps the lower-priced Third Generation model available. However, at less then $30 between the Glock 17 Third Gen and Gen4 CO2 pistols, it is not so much the price difference as what comes at that price.

Overlaying the Gen4 on the Third Gen CO2 model you can see that the trigger is slightly different and the front and rear sights are repositioned to provide a slightly longer sight radius.


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It took Glock years to develop the Gen4 as an improved version of the Third Generation Glock design. For the air pistol versions the work was already done for the most part. What was required rather, was to determine what would separate the Third Gen and Gen4 CO2 models for price, and perhaps the larger question, why did Umarex and Glock not simply go from the entry-level, non-blowback action Glock 19 Compact, to the Glock 17 Gen4. Why the interim model?  While I haven’t interviewed anyone at Umarex or Glock to get an answer (they did it, so that’s that), the design and technical differences in the guns is pretty much self explanatory. Each has advantages over the other. Not so with the centerfire Glock 17 models, the Gen4 is a better gun, but with the CO2 versions there are differences that have no bearing on their centerfire counterparts.

Other key differences are the travel of the slides, the Gen4 slide locks open further back, more closely approximating the centerfire model, the hidden manual safety is silver to duplicate the look of the serial number plate on the bottom of the centerfire pistols, and both show how well all of the safety warnings and manufacturer information is placed on the bottom of the triggerguard and dustcover so as not to detract from the gun’s authentic look.

Why you may prefer one over the other

Let’s start with what has made the Third Gen-based CO2 model so good. We know that it is perfectly sized to the centerfire pistol. We also know that the firing system for this gun uses what I call a short, short-blowback action design, meaning that while the slide travels back almost the full length of a centerfire gun when it discharges, it comes up short when the slide locks back or is manually locked open. We also know that the barrel is not a short-recoil, locked-breech, tilting-barrel design; it is a fixed barrel, like a conventional cartridge-firing short-recoil blowback action pistol, a Walther PPK for example. There is nothing wrong with this; it is just not how a centerfire Glock 17 is designed, but it works just fine for the CO2 model, and with the interface of the CO2 BB magazine and the CO2 firing system, the gun is able to not only generate a respectable sense of recoil but send .177 caliber steel BBs downrange at better than 50 fps faster than any of its blowback action contemporaries, an average of 376 fps. This is all good, you just can’t fieldstrip this gun, and that is not good if you want total authenticity. In order for Umarex and Glock to have a model that could effectively go toe-to-toe with the higher end CO2 models from Sig Sauer and Springfield Armory, that offer total equivalence in handing and disassembly, the Gen4 had to be made as a third (but hopefully not final) step.

On the Gen4 model (left) you can see how the sights are placed closer to the rear and front of the slide. The Gen4 also has more authentic markings on the top of the barrel lug.

So, we begin this second evaluation of the Glock 17 Gen4 model with the most basic requirement, dimensions. First let me get the packaging out of the way. The Gen4, despite it higher retail price and greater number of features, still comes in a blister pack. Comparably priced and equipped models from Sig Sauer and Springfield Armory come in reusable boxes (the Springfield XDM models sell for the same or less than the Gen4 Glock, the Sig Sauer models sell for less). And now, back to measurements.

Locking the slides back tells a story about how different these two CO2 models are internally. The Third Gen model (right) shows the magazine interface with the firing system for the fixed blowback action barrel, while the Gen4 shows the top of the magazine and front of the air nozzle like the majority of blowback action CO2 models that use actual locked-breech designs. Also note the difference in barrel shape and slide contour.

While both Glock 17 models have the same dimensions, overall lengths of 8.03 inches, height of 5.47 inches, and slide widths of 1.0 inches, the Gen4 design is a slightly different shape with a more squared off slide and frame and slightly deeper accessory rail. What this means to holster fit is that a Blackhawk Serpa holster that is made for a Third Generation Glock 17 will not fit a Gen4. You need one specifically for Gen4 models. This is a little less exact with leather holsters, which have a natural give to their shape, even contoured rigs, which is why in later parts of this series you will see me holstering the Umarex Glock 17 Gen4 in a Galco Combat Master holster and not the Blackhawk Serpa Level II holster I have used for the Third Gen pistol. The good news is that even though the CO2 BB magazines for the two CO2 models are a different design (sorry to break that news) they both fit in the same magazine pouches as the centerfire Glock models.

Another interesting change is the finish on the slide. The Third Gen model approximated the Tenifer treated dark black finish that had a slight gloss. The Gen4 uses the later matte (Parkerized-look) finish over a Melonite treated slide. The new Gen4 CO2 model closely approximates that look, while the Third Gen model has a glossier look. This view also shows the difference in the backstrap texturing between the Third Gen (bottom) and Gen4 style. The Gen4 rear sight also has a larger white outline.
The Gen4 CO2 barrel does not tilt up when the slide retracts, although there is a blowback action, locked-breech design being used in the Gen4 air pistol. The side view also shows the differences in grip texturing and the length of slide travel when locked back.

What else is different?

The photos say more than words, but looking at the front of the guns you can see how Glock changed the recoil spring, guide rod design and how it fits into the front of the frame. The differences are very clear. The more squared off lines of the Gen4 are also evident. Some things not quite so obvious are the slightly larger rear notch white outline Glock sight on the Gen4, which is also just a hair further back on the slide, the slightly larger white dot front sight, which is a little further forward, entirely different grip panel stippling, different frontstrap texturing between the finger grooves, a much larger slide release on the Gen4, a slightly reshaped slide release, a change to the Safe Action trigger’s contour, and of course, the interchangeable backstrap panels, with the Gen4’s standard panel being smaller than the Third Gen model’s fixed backstrap, which also has completely different texturing. Other than that, they are the same gun on the outside!

One of the major internal differences is the design of the CO2 BB magazines and firing systems which are different for both guns. Bad news is that Third Gen CO2 mags will not work in the Gen4 guns and vice versa. The Gen4 magazine is similar to those used for CO2 models like the S&W M&P40 only the Glock mag has a decent locking follower and a round loading port. That’s a big plus for loading this style CO2 BB magazine.

On the inside it is hard to say since the Third Gen doesn’t fieldstrip, but when you take the Gen4 CO2 model apart, exactly the same way as the centerfire gun fieldstrips, there is a version of the dual recoil spring design developed for the centerfire Gen4 guns, so even on the inside, the CO2 model is technically improved. How this relates to performance, we will begin to explore in Part 3.

The one thing the Third Gen CO2 model can’t do. The Gen4 fieldstrips just like a centerfire Glock. On face value, this gun is everything you want in a CO2 understudy.

A word about safety

Blowback action airguns provide the look, feel and operation of their cartridge-firing counterparts and this is one reason why they have become so popular. Airguns in general all look like guns, blowback action models more so, and it is important to remember that the vast majority of people can’t tell an airgun from a cartridge gun. Never brandish an airgun in public. Always, and I can never stress this enough, always treat an airgun as you would a cartridge gun. The same manual of operation and safety should always apply.

3 thoughts on “Umarex Glock 17 Gen4 Part 2”

  1. ” and Glock wisely keeps the lower-priced Third Generation model available. ”

    Thank the Lord for that. Because California will not allow civilians to import Gen4 nor Gen 5 models into their wonderful State. Nor is it likely California ever will. 🙁

    But most Gen3 are good to go, i.e. they are on the official California approved roster of safe guns! 🙂

    • I feel for you there. If you ever want to leave the Democratic People’s Republic of California, u can have whatever GLOCK you want here in Iowa…just provided you like snow 5-6 months out of the year!

  2. Well you said part 2 would answer my questions. I wouldn’t get a Gen3 since the mags aren’t the same, that being said, the Gen4 mags look better. The Gen4 is overall a much better effort by Umarex than the Gen3. Now if they would roll out a Gen5 to match my 9mm, that would be really nice!

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