Lower Spikes, Barrel Red X Arms, Receiver?

I have an issue with every other round jamming or not feeding properly. I bought the gun used so Im not sure of the upper parts. Looks like there are no M4 ramps in the receiver. The tip of the bullet stops at the top edge of the barrel extension. You can see a mark where it leaves green paint from the bullet. Should I buy a different receiver with M4 ramps machined already or just match them myself with a rotory bit. I run a lathe and mill so it wouldnt be a problem. Just want input on whats the right way. Thanks

Here's a pic at the rounds.

May have found the problem. What do you all think? The carrier key was loose. I could wiggle it side to side pretty good. Someone's staking job didn't hold.

Our carrier had a loose gas key? Call us and we'll replace it, but it sounds like it is another companies upper on your weapon.

Not yours...

Now I can see the pics. Yea, that staking job didn't even bend the heads of the bolts. If the gas key is wobbling and striking the gas tube, instead of sliding over, it will prevent feeding.