You could definitely go for a glock. I have the model 24 which is a .40 cal target model. Although that ran me closer to $700 brand new. And with the extended barrel its not very good for concealed at all.
I would suggest a mid-size glock and then buy the target barrel later on if you want. It should work in the original slide, but it will stick out a bit probably at least an inch if not more. And I don't know if that would provide good stability in the barrel. Heck for all I know it may actually make it less accurate
As another thought, you could always get a .22 target pistol. They are not overly expensive if you find base models, plus the ammo is dirt cheap. And you could still use the Ruger for self defense if need be.