Central Missouri Machine Gun
Just like everyone else, they have had their ups and down trying to keep up with the last 2 years of huge demand for AR15 rifles. The biggest problem I recall was poor communication with people waiting for an item to ship, often the promised ship dates were way off. BUT, this problem was found at most, but not all dealers.
I personally passed on buying an upper from them, and bought a Sabre Defence midlength instead. I am very happy with the upper, and the service I received from PK Firearms
Edit to add:
The bargain bin rifles are a very good deal ,and generally better quality than the description might lead one to expect