Originally Posted by Underclocked

I think that would depend upon a number of things... how close tolerance your plug's threads are to the barrel's threads, what kind of seal you establish and with what agent (tape, grease, or ?), the design of the plug's nose, and what kind of powder you are shooting. I tighten to just snug but usually with a tool of some sort - no torquing beyond snug.

You have two possible paths for blowback, one past the threads and another from around the primer. Around the primer is generally most offensive and matching the proper primer to your plug can make a huge difference. Blowback past the threads is usually stopped by either grease and/or tape - backing the plug away from the fully seated position could only increase the chance of this type of blowback.

There could be situations where backing out the plug a bit would actually improve headspace and provide better sealing in the primer pocket resulting in less blowback. But I think most designers of breech plugs have the intention of the plug being snugged in place. I don't believe I've ever read an owner's manual that suggested otherwise.