Some gun enthusiasts find the use of the Glock magazine for pistol caliber carbines (PCC) as a bit awkward since when the magazine is inserted on the carbine magwell, it will be of such a steep angle of 15% degrees. Well, at UDMC, we can only agree. However, the use of the Glock magazine for a PCC like UDMC's S9-DBB has lots of advantages not to mention its ready availability in the market owing to the fact that Glock pistols are widely used in the Philippines and in other countries. The Glock magazine also has a very high reliability for feeding the ammunition inside the chamber of an AR platform carbine. Hence, at UDMC, we decided to use the Glock magazine for our S9-DBB.
Other gun manufacturers have also chosen the Glock magazine for their PCC's although they reduced the angle (less than 15%) of the magazine inside the lower receiver magwell, thus, slightly pointing the ammunition upwards. We think that it is not a good idea. That is why in our case, we made sure that the ammunition is directly pointed towards the chamber, thus, eliminating the need for "throating" the chamber which is a bad idea from a safety point of view.
In weapons design and engineering at UDMC, our criteria are 1st-SAFETY, 2nd-RELIABILITY, 3rd-ACCURACY and 4th-LETHALITY. The matter of AESTHETICS or "nice to look at" comes only after the 4 criteria have been met.