Bolt spring for cmmg ar15?

[glock27]

I bought a CMMG Piston AR-15 about a year and a half ago and have had no problems with its operation but I was looking on the CMMGINC.COM website and saw on a parts list that my gun comes with a bolt spring... I do not and have not ever had one of these items in my firearm. Is this thing necessary?
Any suggestions?
http://www.cmmginc.com/pdfs/piston-kit.pdf

 

[remymartin]

 

[sloughfoot]

It is in the parts list and the manufacturer wants it installed in the bolt carrier behind the bolt.

Sooooo.... are you sure there is not one in your bolt carrier?

I am not about to try to supersede the manufacturers instructions.

Even though my knowledge of firearms is vast and flawless.

 

[glock27]

I'm positive that I don't have a spring of any kind in my bolt or carrier except for the extractor. The website lists that spring and also tells you where to put it in the directions...