I notice Black Hills Ammunition (as with other DoD-provisioned 5.56x45 NATO ammo) crimps its 5.56 NATO primers in commercial ammo.  

Question:  Assuming new brass when handloading (i.e. primer pockets are not loose/opened up), what is the operational risk in "not" crimping primers?  What are the odds, assuming properly limiting chamber psi to 62,366 (or 55,000 psi if SAAMI spec .223 Rem), that primers will pop out on a hot day, become lodged in the fire control group, and lock up the weapon?  I'm wondering if the real reason for mil spec ammo being crimped is simply:  (1) over-engineering for safety's sake, and (2) assumes periodic full-auto/3-shot burst/hot chambers.

My understanding is it's just over engineered to ensure reliability in rough conditions with mass produced ammo. No reason to crimp hand loads, you would have to ream or swage the primer pocket every cycle, which I can't imagine being good for case life.

The purpose of crimping primers is to prevent them backing out in automatic fire.  It is a standard requirement for bulk-issued ammunition.  Even the GI .38 Spl (M41, for example) had crimped primers.

Unless you're going to be firing this stuff in full auto, the primers not being crimped is not an issue.

Plus there is no way to crimp primers at the home reloader setting.  
Has to be done at the OEM.  A lot of crimped BHA has been WW headstamped with primer sealant evident.

Yeah, I have several ARs, and have reloaded a bunch of ammo w/o crimping primers.  But I don't use those as improvised SAWs like an M4!

GH Porter has it. The crimp is designed to hold the primer in place during the jack hammer style beating that takes place in full auto firearms. It doesn't matter if it's being fired from a M4 with a 30 round magazine or through a M240 belt fed. The mg's act like a kinetic bullet puller on both the primers and the bullets.

I have swaged more than my far share of primer crimps, I'll be damned if I'm going to put them back in.