Many/most semi-auto handguns are ammo sensitive in relation to feeding due to differnt sizes, shapes and spacing of different kind of bullets.  Most experts agree that a semi auto should be tested with carry ammo and not be carried unless it can shoot 200 rounds flawlessly.

Assuming we are using good quality ammo (like Q313A ect) and, I am just talking about physical feeding, not if there is enough power to cycle, propellant too dirty ect, just feeding.  

Are there feeding issues with ARs?   or is the shape of the projecticle such that feeding is not an issue?

The only feeding issues with mine is that it cannot seem to get enough to eat

Shouldn't be an issue with quality mags. If you're having feeding issues, check out the magpul followers and replace your current followers with those.

SOME open tip/hollow point ammo can hang on the receiver, using some mags that allow the bullet tip to contact the receiver, instead of the feedramp on the barrel extension.  Look at any well used AR and you will see these areas worn just a bit.  It can happen, but it is rare.

That being said - the same logic applies to the AR that applies to handguns - you should test your ammo and *know* that it feed reliably.  However, the AR is much less finicky than most pistols are about different bullet shapes and OAL's.  

I have 5 different AR'S, 4 different name brands and have shot many different kinds of quality ammo through them with no issues. I don't shoot the really cheap stuff though. If you keep them relatively clean and shoot decent and tested (in your gun) ammo, you should not have any problems.

My Shorty Bushmaster A1 is a whore it will suck any round I feed it!
Im getting close to the 2000rds mark. Still brand New Looking
It has never Hic Up