Original info courtesy of:
G20-IWB24/7 , with some additions made later.
GLOCK model number descriptions:G17 9mm Full-size, 17rd mags, 4.5” bbl
G17L 9mm Full-size, Longslide, 17rd mags, 6.02” bbl
G18 9mm Select-fire (same size as G17) 17 or 33 rd mags, 4.5” bbl
G19 9mm Compact 15rd mags, 4” bbl
G19X 9mm Full Size/Compact Hybrid, 17rd mags, 4"bbl - full size frame with a compact slide (FDE only)
G20 10mm Full-size, 15rd mags, 4.6” bbl
G21 .45ACP Full-size, 13rd mags, 4.6” bbl
G22 .40 S&W Full-size, 15rd mags, 4.5”bbl
G23 .40 S&W Compact, 13rd mags, 4” bbl
G24 .40 S&W Full-size, Longslide, 15rd mags, 6.02" bbl
G25 .380 Auto Compact, 15rd mags, 4” bbl (not sold to the public in the US)
G26 9mm Subcompact, 10rd mags, 3.5” bbl
G27 .40 S&W Subcompact, 9rd mags, 3.5” bbl
G28 .380 Auto Subcompact, 10rd mags, 3.5” bbl (not sold to the public in the US)
G29 10mm Subcompact, 10rd mags, 3.8” bbl
G30 .45ACP Subcompact, 9/10rd mags, 3.8” bbl
G31 .357sig Full-size, 15rd mags, 4.5” bbl
G32 .357sig Compact, 13rd mags, 4” bbl
G33 .357sig Subcompact, 9rd mags, 3.5" bbl
G34 9mm Full-size frame, “competition”-length slide, 17rd mags, 5.3” bbl
G35 .40 S&W Full-size frame, “competition”-length slide, 15rd mags, 5.3” bbl
G36 .45ACP “Slimline” (single-stack) Subcompact, 6rd mags, 3.8”bbl
G37 .45GAP Full-size, 10rd mags, 4.5” bbl
G38 .45GAP Compact, 8rd mags, 4.0” bbl
G39 .45GAP Subcompact, 6rd mags, 3.5” bbl
G40 10mm Full-size frame, longslide, 15rd mags, 6.02" bbl
G41 .45ACP Full-size frame, "competition"-length slide, 13rd mags, 5.3" bbl
G42 .380 Auto Subcompact, 6rd mags, 3.25" bbl
G43 9mm Subcompact single-stack, 6rd mags, 3.39" bbl
G43X 9mm Compact/Subcompact Hybrid, 10rd mags, 3.41" bbl - compact length frame with subcompact size slide, slimline single stack
G44 .22lr Compact, 10rd mags, 4" bbl
G45 9mm Full size/Compact hybrid, 17rd mags, 4"bbl (Same gun as 19X but in black)
G48 9mm Compact single stack, 10rd mags, 4.17" bbl
Last, but not least, the “Glock 7,” which is a “porcelain gun that costs more than you make in a month!”
Models by Caliber:9mm:17, 17L, 18, 19, 19X, 26, 34, 43, 43X, 45, 48
.40 S&W22, 23, 24, 27, 35
45 ACP21, 30, 36, 41
10mm20, 29, 40
357 Sig31, 32, 33
45 GAP37, 38, 39
380 Auto25, 28, 42
.22lr44
Model numbers by frame size:Full-size17, 17L, 18, 20, 21, 22, 24, 31, 34, 35, 37, 40, 41
Compact19, 23, 25, 32, 38, 44, 48 (Slimline)
Hybrid19X, 45 (full size frame, compact slide)
43X (compact length frame, subcompact slide)
Subcompact26, 27, 28, 29, 30, 33, 39, 36 (Slimline), 42 (Slimline), 43 (Slimline)
Extra Model Designations:An “
SF” after the model number indicates “Short-Frame” which is a reduction of the amount of material in the backstrap, for a better grip with smaller hands. The grip reduction is from the front and back of the grip. The sides are the same width apart as non-SF frames. (Currently, only G20, 21, 29 & 30 are available as “SF” models)
Note: the G21SF has been made in several variations, including with or without an ambidextrous magazine release, and with either a standard "Glock" light rail OR a 1913 Picatinny Rail.
A “
C” after the model number indicates that the gun is "Compensated" (ported) from the factory. Two small ports in the barrel with corresponding vents in the slide are present on either side of the front sight.
MOS stands for Modular Optic System. Certain Gen 4 and Gen 5 models are available with the MOS feature, meaning that the pistol is optics ready. A pistol with this designation includes a set of plates which allow various optics to be mounted to the slide. The included plates are compatible with Eotech/Docter/Insight/Meopta, Trijicon, C-More, and Leupold
Longslide indicates that the model has a full size frame with a 6" barrel and extended length slide. This is available in the 17L (9mm), 24 (.40 S&W), 40 (10mm)
Competition indicates that the model has a full size frame and 5" barrel. It is often used in competition shooting such as USPSA/IPSC. This is available in the 34 (9mm), 35 (.40 S&W), 41 (.45 ACP)
Generation Differences:Gen 1: No finger grooves, no accessory rail, pebble-texture grip.
Gen 2: No finger grooves, no accessory rail, waffle-texure grip
Gen 2.5: Finger grooves, no accessory rail (only on some G29/G30’s)
Gen 3: Finger grooves & rail (no rail on 9mm/.40/357/.45GAP subcompacts, rail on .45ACP/10mm subcompacts). A new Gen 3 comes with 2 magazines.
RTF-2: Indicates a Gen 3 gun that has a very aggressive pyramid texture on the grip for use in weather/extreme situations.
Gen 4: Finger grooves & rail, interchangeable/mountable backstraps, ambidextrous magazine release (can be switched between right and left-handed but not both at the same time), has a less-aggressive “rough texture” pyramid-style texturing on grip (than the RTF-2 grips). A new Gen 4 comes with 3 magazines.
Gen 5: No finger grooves. Has rail, interchangeable backstraps, same rough texture as Gen 4, improved trigger, "Marksman" barrel, DLC finish, ambidextrous slide stop lever & magazine release, and flared mag well. Gen 5 only available in 9mm offerines. A new Gen 5 comes with 3 magazines.
General Information:Magazine interchangeability:Higher capacity magazines from larger Glock pistols will work in the smaller Glock pistols of the same caliber (they just hang out the bottom a bit). Example: A 17rd 9mm mag for a G17 will work in the subcompact G26. Exception:single stack guns such as the G36 and G43.
Caliber interchangeability: A .40 caliber Glock can be converted to .357 Sig and vice-versa with a barrel swap to the other caliber. Example: To fire .40 S&W out of a G32, you would replace the G32 barrel with a G23 barrel. It is wise to use different magazines, marked with the correct caliber, as to prevent mixing ammo/bbls, but not absolutely necessary. Some aftermarket firms offer a 9mm conversion barrel for the .40/.357 Glocks, which require using the matching 9mm mags from the corresponding frame size. Example: G23 with a 40-to-9mm bbl would use G19 mags.
Additional information: Here's a helpful link that has some great pictures of the differences between generations (1-4).
https://reducerecoil.com/2015/03/differ ... lock-gen4/