My Ruger American 223, AR15 magazines, won't feed.  The cartridge comes up properly, but then the bullet hits the face of the barrel instead of going into the chamber.  I've tried different magazines, different seating depths, different bullet shapes... all the same problem.

Are there any solutions short of trading it off??

I have a ruger American special run with a heavy barrel and magpul stock that does the exact same thing. Nose catches on the barrel and stops cold. Tried a few different mags. Makes no difference. Needs a spacer added to the barrel face to bridge the gap where it threads into the receiver.

Wouldn't that cause the bolt to then hit the spacer and fail to close?

I have a half-assed solution.  After talking to my son that had a Savage 223 that did the same thing, he said it would run if you worked the bolt as fast as possible, so I tried that.  It does work, but not the best solution in my opinion... not many times I've been charged by a herd of gophers or jackrabbits.  

Might maybe make a tapered (coned) spacer and turn the bolt locking lug faces at an angle to match the spacer??  I"m no machinist, and would have to have this done by someone that knows what they're doing... $$$

Put up a few photos of pre feed then a few of feeding. I’ll look at it and come up with something. I would also compare it with other mags. The magpul may have different feed lip geometry, just enough to make it snag.