[redscho]

I was in my local gun shop this morning and looking at the Mossberg MMR Hunter (AR-15). The clerk said that it was chambered for 5.56 X 45 (NATO) only and .223 Remington could not be used. I have never heard of this before. I know that you should not use 5.56 NATO in a gun chambered for .223 but have always thought you could use .223 in any gun chambered for 5.56 NATO. What is going on here? I have checked Mossberg site as well as a couple of reviews on this rifle and none mention that it cannot be used with .223 rounds. All say 5.56 NATO/.223.

[trip286]

Just because a man sells guns, doesn't mean he knows everything about them all. I had to show a ten year veteran tire and lube tech where the oil filter was on my old Cadillac.

If you want the must definitive answer, contact the maker.

It is, as you seem to know, generally accepted that you can run .223 through 5.56 though, but not encouraged to do it the other way around.

[robocop10mm]

Gun store employee was mistaken (or is an IDIOT!). I would give him another chance to insure you heard him correctly. If he is, indeed, an diot, ask to speak to the manager/owner. He/she needs to know what kind of mental midgets are working there.

[c3shooter]

What Robo just said up there. ^^^^

Without realizing it, you had wandered into the Bozone Layer.