Let's say ALL that stuff happened, all at the same time, and the magazine was rusty, and the floor plate fell off and the spring shot out.... and anything else you could imagine to cause a horrible malfunction.... then the cartridge gets seated in the chamber, behind a locked bolt, at least a full inch away from the offending magazine, surrounded on all sides by tempered steel that has nothing whatsoever to do with the condition or make of the magazine. As the fire control group is activated, in a section of the lower receiver completely partitioned away from the magazine, it strikes the end of the firing pin which then rockets through the bolt carrier assembly, and impacts dead center with the primer, all the while never making contact with the catastrophic magazine. As the primer pops, it ignites the powder, creating an expansion of gas that travels the path of least resistance. The bullet is quickly uprooted from the casing and sent hurtling through the barrel (also not in contact with the ill fated magazine). As the bullet passes the gas block, the expanding gasses begin the auto loading function of the firearm....
I got side tracked.... at what point did you say the magazine affected the path, performance or trajectory of the bullet to cause it to err?
You could make a magazine out of a "Mike and Ikes" box and some spare parts out of the garage. If you get it to load a round, your rifle will be just as accurate as if you used a Magpul/KAC/DPMS/??? Magazine.
This is untrue with Armalite AR10 mags. Eugene Stoner patented a feature that makes the AR10 kill deader than other rifles. I heard a sniper actually killed his target three times with one shot. Now that's REALLY DEAD! It's true because I read it on the Internet.