I always get a good laugh about folks getting so upset about the lock. At least on the 640 series. In fact I never notice mine until a internet whining session starts about them. These guns are not high end guns.They are Practical, efficient EDC guns. I doubt any bad guy that gets shot by one is going to com,plain about the fact that he is insulted because the gun that shot him had a lock hole in it.
Don't like it, don't buy it, no big deal. Or get a Ruger Great trigger right out of the box. I had to put a new spring in my 642 but not a big deal just extra cost.
I also laugh at the internet when they say "Some will fail under heavy recoil. Never knew anyone to have one fail in my years as a RO at my club.I wonder what kind of over the top load would cause that. Guns fail for many reasons. Worry more about the idiot text messaging that you might meet up with when going to the range.