Here are the differences in the ‘M’ pistols used by agencies such as the FBI, DOS/DSS, ATF, DEA, USMS, and USMC CID, as well as the consumer Gen 5 guns vs. the Gen 4 pistols:
- No finger grooves.
- Flared mag well.
- Ambidextrous one-piece slide stop lever – on many of the ‘M’ guns, it’s also an extended ambi slide stop. That extended ambi slide stop lever is part # 33797, and is available for sale to certified armorers. It now appears that the extended ambi slide stop lever is on the Gen 5 G34.
- Front of the slide is rounded to match the Gen 4 subcompacts and long slide models. When first introduced, the Gen 5 and ‘M’ frame weren’t beveled to match. That has since been resolved in newer Gen 5 pistols.
Land and groove rifling instead of polygonal
- Gen 5 GMB (Glock Marksman Barrel) barrel has a target match crown (FBI ‘M’ guns don’t). G17 barrels cannot be swapped with other generation guns – mainly due to the differences in locking blocks (now the same as the other 9mm pistols) and newer, longer, RSA.
- Same style firing pin safety (angled instead of flat) as the Glock 43
- Return to two-pin frame due to a redesign in the locking block area of the frame that removes the need for the third pin.
- Slide lock spring similar to Glock 43 (coil vs leaf), and the slide lock is moved slightly rearward.
- Return of cutout on bottom of front strap to assist with stripping magazine (such as due to a double feed) that were originally in Gen 1, Gen 2, and early Gen 3 full sized guns. Early prototypes did not have this cutout, which is why it’s not visible in some early pics. This cutout is on the 17, 19, and 34, but not the 26. The 26 has the extended toe similar to the MHS and 19X frames. It is also not on the Gen 5 MOS guns. Note that this was eventually removed from the Gen 5 pistols in summer 2019.
- Tougher finish applied to the same Melonite metal treatment process. This finish is dubbed nDLC (diamond like coating) that is similar to the black nitride finish. Glock refers to it as an ion bonded finish, and will only be available on Gen 5 and M guns.
- The upper cartouche, the flat area on the upper right grip area that show where the pistol was made, has been moved down and combined with the lower one, which contains the patent number
- Mags have an orange mag follower
- Mags have extended front lip to aid in reloading
- Mags have a slightly rounded base plate (bottom front edge)
- Initially, there were no front serrations on the regular 17 and 19, as some people claim, or as some photoshopped pictures suggest. Glock added an LCI to the guns many years ago to negate the need for press checks. Front serrations were eventually added to all Gen 5 pistols except the 19X in summer 2019.
‘M’ guns come with 6 magazines. Gen 5 guns come with 3.
- Gen 5 is available with polymer sights or several night sight variations, including factory and Ameriglo ‘Bold’ night sights. The new sights are narrower than previous models. ‘M’ guns have slightly different sights than the Bold sights. These are called the ‘Agent’ sights. Differences being FBI sights have a ‘U’ shaped notch in the read sight, whereas the Bold have a square notch. Both rear sights are serrated, and the night sights don’t have a white or colored ring around them (this is often referred to as ‘blacked out’). Both the Gen 5 Bold sights and the FBI sights are available with a .125 orange front sight as well as a more traditional .140 width sight.
- Glock had originally said no plans for MOS guns, but they have released the Gen 5 G17, G19, G26, G34, G45, and G47 in MOS configurations.
- Glock said originally that the Gen5’s will only be offered in 9mm, but São Paulo Police Department (Brazil) has deployed the Gen 5 G22, which includes a manual safety like the 17S and MHS pistols. Glock has since released .40 cal Gen 5 guns 22, 23, and 27.
- New striker, but same spring cups, spring, and sleeve
- New extractor
- New slide cover plate
- New trigger mechanism housing
- New trigger bar, but the Gen 4 dimple is removed (since the Gen 5 went to the angled trigger safety, the dimple is no longer needed)
- Gen 5 doesn’t use the ‘S’ shaped coil trigger spring, like the previous generations, instead going to a setup like the slimlines
- G19 and G26 come with a smooth trigger (like the 17) instead of the previous grooved trigger.
- FBI ‘M’ guns have the nDLC finish on some internals including the trigger bar, connector, and slide stop lever, Gen 5 guns do not. Also, ‘M’ guns that went to a select few agencies do not have the nDLC treated internals. It’s easy to spot the difference, as the nDLC finished internals are jet black. Not gray.
- ‘M’ guns appear to have an extended and rounded mag catch as stock, vs. a normal mag catch for the Gen 5 guns
- ‘M’ gun is also available as MOS
- Gen 5 are currently available in black, FDE, BFG, and gray, although the FDE and gray guns were early Gen 5 with the non beveled frame, and front cutout. ‘M’ guns are available in several color molded frames.
- Black is standard issued to all agents.
- BFG is issued to FBI SWAT
- FDE is issued to FBI HRT
- Gen 5 guns have a ‘5’ rollmark on the top of the barrel. ‘M’ guns have an ‘M’ or ‘5M’.
- Gen 5 G34 doesn’t have the cutout on the top of the slide like previous version, yet still maintains good balance due to a re-engineering of the materials used in the slide.
- Gen 5 pistols have a rail that uses the 1913 picatinny dimensions.
- Gen 5 G19 and G45 are available in TB versions, with factory threaded barrels and Ameriglo suppressor sights.
- Newer production Gen 5 pistols have an enhanced breech cut that greatly improves ejection of spent casings. I’ve not seen this new breech cut on any of the ‘M’ guns.
The new mags will work in previous generation pistols, and vise versa, with the exception of the 21SF with picatinny rail & ambi mag catch, and the 19X.
Keep in mind that the ‘M’ pistols are Glock’s specific response to the FBI requirements for a new pistol. Just because any of these features exist on these guns does not mean that they will appear in any other non-‘M’ guns in the future.
The following pictures of the Gen 5 G26 and G34 are from Glock.
3 Replies to “Differences between Gen 4, Gen 5, and M pistols”
Please advise what parts are and are not interchangeable on the Gen 3, 4, & 5 G-26’s
Thank you for your help and assistance
I just acquired a 19M and noticed that it only has a ‘5’ rollmark on the top of the barrel. Are all ‘M” guns supposed to have a ‘M’ or ‘5M’ on the barrel?
No. Newer, non-FBI M pistols have a 5 on the barrel hood.