Well I had been putting this off, but I finally decided I wanted a magpul stock and the only one I found local was milspec sized... so I figured why not just replace the commercial receiver extension while I'm at it with milspec.  Glad I did, there is a significant difference in how tight the threads mesh between the commercial and milspec tubes.    I had to file out the inside of my receiver plate to get it over the threads of the milspec buffer tube.  When threading it into the receiver it was clearly much more snug, and the castle nut as well.

After seeing how loose the commercial buffer tube was I am glad I never had a jam which required me to slam the butt stock on the ground .. could have been ugly.

So while the while process was not cheap, I would say it was definitely worth it.  The magpul parts feel a lot more comfortable, stock is a lot more solid feeling, and the milspec tube is definitely a good idea (because of the taller threads).

ymmv.

Since nearly every thread needs at least one picture I will include one.  Will probably add an eotech and quad rail in the near future.  

Thanks for the input.

I just completed one build, and have another in the process, and have already completed the lower.  I went ahead and went milspec and am glad to see a justification for the extra cost.

nice! can't wait for my Magpul stock too and my new milspec buffer tube;)

Same here .. just replaced two commercials with mil-spec, one for LMT SOPMOD and one for MAGPUL ACS. They definitely are a tighter fit on the receiver and on the stock itself.