I have posted on this before and others disagree. Their right. However the differences are this;

Military brass is slightly harder than commercial brass. A "must" as military ammo is subject to rough handling.

Military brass is slightly thicker, not because of the charge, but again to help resist deformation as a result of rough handling. This difference will result in different chamber pressures as a result of a SLIGHTLY reduced case capacity.

The differences in case dimension when one refers to FACTORY drawings? There isn't a nickles worth of difference. In fact they are essentially identical in dimension. My opinion, but when somebody starts worrying about .002/.003 in a drawings dimension they should get another hobby as the manufacturing tolerances ranges of bullets and chambers are usually greater than this.

Already mentioned, but military chambers are more generous. Matter of dirt and carbon in battle and reliable functioning. It may be worth it to mention that machine guns use the same ball ammo as rifles and their chambers are even bigger yet, and they don't split cases except on occassion.

There has been semi-auto rifles that I know of ruined in the past from the use of commercial ammo. However these rifles were found to have been firing commercial ammo of a MUCH heavier weight than what the rifles were designed for.

When one compares commercial ammo to military ammo, of the same weight, one will find that the pressures aren't all that far different, and the differences are usually well within the pressure range of the "blue pills" that each and every rifle fires when originally manufactured. As a matter of safety all rifles are designed to handle a greater pressure than it will generally fire.

I have no problem firing commercial ammo in any of the rifles I own and I don't think any one else will if one stays in the same bullet weight range. Always lighter, but NEVER heavier. Especially with semi-auto rifles.

The only reason that a commercial case may be harder to re-size after being fired in a military chamber is that it's case walls being slightly thinner, it will "spring" to a slightly larger size. However I have fired commercial cases in both bolt action and semi-auto rifles (reloads to be sure, about 10% under the military loading) and still reloaded them 5 to 6 times for sure, maybe more for some.

You do what you gotta do.

My 2 cents.

eb