.45 GAP

    This pistol cartridge was designed specifically on the request of Glock gun manufacturers. It was designed because the Glock wanted a bullet with similar ballistic performance as .45 ACP but could also fit in more compact pistols. 
The GAP there fore means Glock Automatic Pistols. 

.45 GAP compaired to .45 ACP

   The .45 GAP has the same diameter as .45 ACP but is shorter compared to it, also it has shorter primer compared to .45 ACP. Initial development of .45 GAP had lighter bullet compared to .45 ACP, there fore .45 GAP operates at higher pressure. But because of the smaller size of this bullet the increased pressure of this cartridge was to be obtained through selection of powder only. 
The maximum bullet weight for .45 GAP is 15 Grams.

  The .45 GAP is quite popular with both civil and law enforcing agencies because of its ability to have ballistic performance of .45 ACP while having its smaller size. Making it a good choice for concealed carry weapons, and machine pistols.

Ballistic Performance:

Bullet weight/type	Velocity	Energy
185 gr (12 g) Gold Dot JHP	1,150 ft/s (350 m/s)	543 ft·lbf (736 J)
200 gr (13 g) Gold Dot JHP	1,050 ft/s (320 m/s)	490 ft·lbf (660 J)
230 gr (15 g) Gold Dot JHP	935 ft/s (285 m/s)	447 ft·lbf (606 J)
230 gr (15 g) FMJ-FP	940 ft/s (290 m/s)	451 ft·lbf (611 J)
Test barrel length: 4.49 in