I have a Ruger Mark III hunter with a 4.5" barrel. The whole gun is stainless steel. Has a nice balanced weight and shoots great. If you do look at one stay away from the standard model as the front sight cannot be changed. Go for the target, hunter or competition models. The only downside is the gun can be quite a pain to field strip and clean.
The gun has shot every ammo I've put through it, most of which being bulk Federal or CCI. I've had a handful of FTE due to grime and powder caked behind the ejector after 500+ rounds.
The ruger would be great to fit your needs as a trainer and pinker. The gun has magazine disconnect which doesn't allow the mag to drop while the bolt is back. Drops down about half an inch and you must manually remove it. As well a loaded chamber indicator. Both are great for helping new shooters. The gun can also be modified to remove these features. The gun also comes with a weaver mount for optics.
If you have any other questions let me know.