Recently acquired a SS Ruger old army. I have a ultrasonic cleaner that might help to get it cleaned up.... But, what should I put in it?
Any suggestions, was thinking simple green.

I used Purple Power in water some years ago. (Similar to Simple Green) We ran the tanks around the clock until the job was done, changing the solution twice a day for about 2 weeks. Run in detergent till clean, then rinse in hot water with Ballistol, which prevented flash rust.

One warning! Do not clean anything anodized aluminum in hot detergent! It would sometimes make the anodizing pop off the aluminum, sometimes clean white, sometimes spotted. I think there might have been a slight current between the aluminum and the stainless tank.

I've used rubbing alcohol in my ultrasonic to clean blued steel, don't know if it would harm anodized aluminum.

Thanks, this firearm is stainless so no worries there. Not familiar with purple power, maybe something NAPA has or Wally world?

I clean clocks in my ultrasonic. I use diluted simple green, then rinse and shake dry and fill cleaner with alcohol and run again to drive out water.