Why are some mags straight and some bent? For instance, MP5 9mm = bent, MP5/10 and 40 = straight; HK416 = bent but HK417 = straight...? It seems to go by caliber for rifles i.e. .308 = straight and 5.56 = bent, but proportionally they are the same. And on another note; early Waffle mags for the MP5 9mm were straight although according to HKPRO were unreliable with JHPs, why might that be? Anyone able to enlighten me?