I have been working on a model 62 that I discussed in a recent post. I started this new post so as to have the title reflect the issue in question. I searched the internet and this site for information about my issue and came up with very little. As the title of this post states, it is about the breech block lock (action slide lock). This is a model 62 with the single pin system. Serial numbers roughly 20,000 to 98,000. With this system, the slide is locked forward when the hammer is back or in safety mode by a part called the breech block lock. There are references to this being the problem worn part when the slide will not stay in the locked position. I ordered a new one and when installed, the problem is not fixed. In doing some digging, I found the following post https://winchestercollector.org/forum/winchester-22-rim-fire/model-62-problem/

One of the posters made the following comment that was not commented on further but I think this must be a common problem.

I had installed a barrel liner and reblued a mistreated model 62. When I reassembled it I found that the breech bolt did not lock. It sat in the cabinet for a couple years until today. I had to weld up and refit the engagement surface on the (bolt lock?) so that it firmly held the action slide firmly in the forward position. A very tedious and time consuming job. Better than new now. I have a picture but can’t figure out how to upload it.

I believe what he is describing is the same issue that I have. The slide action fits into the bolt and is held in place by the breech lock when in locked mode. But if there is excessive wear in the bolt slot where the slide action pivots, it allows the slide action to slip past the breech lock and allows the slide to open. The poster above appears to have fixed this problem by building up the surface. A new bolt would correct this but I am unsure if there are any available. A used one may have the same problem.
I have built up the area with epoxy putty as a trial and it has fixed the problem. It is a thin layer and I would not expect it to last very long but it did fix the problem. I am not capable of building up metal so I will either not worry about it or locate a gunsmith who can repair it. I will keep the new breech block lock that I purchased as maybe the old one had some wear that contributed to the problem. But it is apparent that it is not the only worn part that can cause this issue.
I hope this helps someone in the future. And thanks to Erin for the final input on my previous post.

Rick