The trouble with this question, which is always cropping up, is that there are really three reliability issues - the gun, the ammo, and the magazine(s). It is like a three-legged stool and we all know what happens with those if any of the three legs breaks while we are sitting on it.
The gun may perform perfectly with that magazine or that ammo, yet be a boat anchor with another magazine or another ammo. Or your XYZ Co. Model X might work perfectly with everything you feed it, while my identical gun is a "jam-o-matic".
There is also another issue with ammo. I know a guy who had a good (make not relevant) pistol and felt it was very reliable. Yet he practiced with the least expensive ammo he could buy while reserving the "high price spread" for carry. One day at the range, i suggested he shoot some of his expensive ammo. Finally, he did so, with great reluctance, thinking about the cost. Well, nearly every round failed; failed to fire or failed to feed or failed to extract or failed to eject. That "ultra reliable gun" was a disaster with the ammo he would have bet his life on.
Jim