Just wondering if the SAR-3 is compatible with M193 or M855 mil-spec ammo or whether it would only be safe with SAAMI spec .223 loads. Anyone know? If it is, I might someday buy one just as a gun to throw around because it is so inexpensive and if it can use ammo compatible with my current AR loads.

Although I can't exactly answer your question, I'm probably not telling you something that you don't know, but SAR-3's do not have tight tolerances on their chambers.   They function great on steel cased ammo.  Mil-spec brass case should be okay, however there have been reports of them ripping the heads off of the cases.   AK's extract pretty hard.  

You might be better served asking your question over in the AK area.

Get one.   I like mine.

Never, ever heard of one not accepting ammo of any flavor. Accuracy changes with quality, but it'll run. But the SAR3 does prefer E Ger Weiger mags. Seems even the AK is not immune to 223/556 mag challenges.
The SAR2 in 5.45x39 is every bit as reliable as the 7.62x39 AK.

Three of the four I checked headspace on were smaller then either SAAMI or NATO specs.

Hey 777, can't get away from you!