The maker of my tank (Sharper Tek) warns that "mirror finishes on aluminum can be dulled" from cleaning in an ultrasonic tank, and recommend use of a "dispersion plate" they sell if you're going to be cleaning mirror-finished aluminum pieces. I don't believe the same applies to the hard-coat anodized surfaces of an AR upper and lower, but who knows?

I use simple green aircraft as my detergent, and haven't noticed any negative effects on the uppers or lowers I've cleaned in my tanks, but I haven't gone through a dozen cycles on any of the parts yet, as I only dunk the rifles if they're extra filthy (usually after MG rentals), otherwise I still just clean by hand. I've also done big batches of magazines in my tanks, using one for a simple green cleaning pass, then a quick dunk in light oil to displace the water and lubricate them before letting them drip drain and air dry.

I have several smaller tanks I use for BCG assemblies and other small parts - but those are steel, anyway. For large enough tanks, handguns can just be dropped in the basket with the slide locked open, or cylinder swung out. Single actions I disassemble and drop the frame and cylinder as two pieces.

Quote Originally Posted by Brian View Post
Sorry, I didn't word that very well, but that was my point. I've heard very mixed reviews on what you can and cannot use in one of these. Hornady clearly advertises it's made for cleaning upper receiver groups and small parts, but then the vast "wisdom" of the internet seems to claim you can't dump your lower in it, or it will dissolve into fairy dust or something. I shoot a lot suppressed, and the idea that I could disassemble the gun and drop it in a tank, dirty mags and all, is really appealing. But not if it's going to somehow mess with the anodizing or something.

Would really like to hear from someone who has dunked their AR a few dozen times.