Reddit reviews Magpul 223 Dummy Rounds (Pack of 5)

Nope, depending on the type they're either spring loaded primers on an aluminum body or with a rubber primer or completely made of hard Polymer Plastic. The hard plastic ones are just called dummy rounds. The ones I linked above are actually just a rubber primer but with an aluminum body. But they do come in spring loaded primer versions.

I bought these for my AR

I would get some dummy rounds. I don't like to dry fire anything, although the ar15 can be dry fired. They are useful for several other things including simulating misfires.

First, check if it feeds manually, by charging the rifle and letting the bolt freely fly back into battery. Find old brass if you're not willing to use a live round, chamber the rifle and see if it extracts without a mag in it. Just do it for giggles. I expect it'll function just fine without the magazine, but it's important to check just to be sure.

Proceed to go to a safe area and attempt to manually feed live rounds from the mag. If this is not an option, get some dummy rounds and do it: https://www.amazon.com/Magpul-MAG215-BLK-Mag215-BLK-5-56-Dummy/dp/B006QP76CI

So, assuming it fails to charge manually, here are the potential culprits:

1. Magazines
   
2. Magazine release
   
3. Bolt catch
   
4. Charging handle
   
5. Bolt/BCG
   
6. Forward assist
   
7. Feed ramp
   
8. Buffer/spring/tube
   
   The alignment/placement is off on one or more of these items if it's failing to feed manually. Go through them one by one and ensure they're up to spec.
   
   If it charges manually, it's likely either a gas alignment issue (tube or block), or the gun needs a liberal cleaning.