If by "mil spec" you mean that all of the standard accessories will fit, the the cheapest ones are the UTH rails at about $75. I've read enough good reviews to say that if that's all you have to spend they will probably get the job done for you (the standard internet disclaimer that they are not a good idea if your life may depend on them applies )
The next price break for rails is in the $150 to $200 range, which will bump up the fit and finish somewhat. That puts you in Surefire territory....
If you're going to splurge, get the Daniel Defense Omega rails. Free-floating, but easy to install and remove, requires no gunsmithing whatsoever. Everything about them smokes the Troy rails, including weight, width, and stability.
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