Since you brought it up...
I have heard some of the reasons for the existence of the 45 Glock. One is the ability to put a .45 caliber cartridge in a frame the size of the Glock 17. Okay, I guess if you are a serious Glock enthusiast that may matter to you. I will admit that the Glock 21 and 30 are a bit on the chubby side when it comes to the grip. What about the 36, you ask? Well, the complaint I've heard is the grip may be slim but it is also too long, making it uncomfortable to shoot. A Glock shooting a .45 caliber bullet with the same frame dimensions as that of their 9mm sounds like a great concept. If it had been executed with the .45 ACP cartridge. The 45 Glock? I think it is a big mistake.
For years Hirtenberger has been loading the .45 Automatic Short. It's based on the .45 ACP case shortened by one millimeter. Their advertised muzzle velocity for a 230 grain FMJ is 835 fps. What was the purpose of this stubby .45 ACP derivative? For the countries that did not allow civilians to own .45 ACP chambered autoloaders (France, Italy, Mexico, & others) this was the answer to the problem.
Now we have Gaston Glock and his very successful autoloader design. He made his success on the original model 17 and 19, then added many more. But take a look at the rollmark on the barrel hood of some of his models. The .40 S&W is not rollmarked .40 S&W, but instead .40. The same is true with the 357 SIG and even the old .45 ACP. While that may be a means to simplify their markings it can also be looked at as a man with his name on his gun not wanting anyone else to have their name next to his. Rumor has it that Cor-Bon had approached Glock some years ago about chambering a model 21 for their yet-to-be-released .400 Cor-Bon. For whatever reason that went sour and Cor-Bon went on to release the cartridge alone. Later when Triton introduced the .40 Super cartridge to the market it too was passed by the people at Glock. They tested a model 21 and 30 with Bar-Sto barrels chambered for this hot cartridge. They were supplied with ammo, barrel reamers, pressure data, etc. During the discussions one thing was brought up repeatedly. If Mr. Glock were to approve of this cartridge and come out with a new gun, he would want to name it the .40 or .400 Glock. Well, I guess that would have been acceptable. Why not, the attention the cartridge would get and the potential of every other ammo maker latching on to it was great. Unfortunately, like many other projects, this one did not see the light of day. It did, however, show a pattern of things to come.
Now, a few years later we have the introduction of the 45 Glock cartridge. It definitely serves the purpose of having a cartridge with Mr. Glock's name on it but does it bring anything to the table for the end user that is new? Lets look at the ballistics. Glock did the right thing by turning to ATK for their cartridge development. By making that one stop they get the talent of Alan Corzine (one of the top bullet designers in the world) coupled with two ammo companies, Federal and Speer. So initially it's Speer that gets a crack at this "new" design.
We all know the cartridge case is shorter than the .45 ACP. How does it compare structurally to the old .45 ACP? The pressure limit for the .45 ACP is considered ancient by many at 19,000 PSI. Even +P loads at 23,000 PSI seem tame compared to 35,000 PSI for the .40 S&W. There have been improvements over the years in brass construction with the .45 ACP. The web area has been thickened and the brass itself stronger, making the .45 ACP case able to hold up to greater pressures. The 450 SMC and .45 Super cartridges are just beefed up .45 ACP cases for that matter. Now if Glock is going to prevent another long chain of gun failures their new case must be made stronger than conventional .45 ACP brass. Without sectioning a case that remains to be seen if it in fact has been done. We do know, however, that the only loadings that will be available will come in the 185-200 grain weight. That tells me that they cannot use a 230 grain because of case capacity issues. The important thing here is they have been able to match but not surpass the ballistics of .45 ACP+P.
Now the question remains, why a 45 Glock? It does serve the purpose of making a smaller Glock able to toss a .45 caliber bullet. Then again, years ago the same was being done with the Detonics Combat Master with .45 ACP and even .451 Detonics Magnum. Will the other major players (SIG, S&W, HK, Taurus, Beretta, Colt & all their knock-offs) step up and offer an autoloader in this cartridge? That is where I would need the crystal ball. The same holds true for the other ammo makers.
In recent years we saw the same thing happen with the release of two competitive cartridges, the .356 TSW and the 357 SIG. Both were able to deliver a 9mm bullet at velocities greater than any 9mm+P+ load on the market. The TSW had the edge with magazine capacity but for reasons left up to debate, the 357 SIG took hold and the TSW fell into the history books next to other cartridges like the .41 AE.
Personally, I will stick to anything chambered in .45 ACP and watch the 45 Glock debate from a distance.