I have two questions:

How can you tell if your Buffer Tube is Mil Spec?

Maybe this can help the question; Does Bushy put any Mil Spec Tubes/Buffers in their Preban config M4's?

Situation is that I have two Magpul M93Bs. One I got from Grant with a H buffer and Spring. The other I got from ebay w/o Buffer and Spring. Im going to put the one I got from Grant on my M4 and I want to use the leftover spring and buffer from the factory telestock and use that in my other M93B on my other bushy to replace the A2 stock. Does that make sense?

Quoted: Does Bushy put any Mil Spec Tubes/Buffers in their Preban config M4's?

No.