Hello all, I am new to this forum and could use some help. I can't seem to find the answer to this question. I have a Mod 4566 and have tried every allen wrench I have to fit the rear novak site. Does anyone know the allen wrench size? Thanks much

1/16" (0.0625")

But be prepared for problems, even if you know the size.

On the first police surplus 5906 I recently purchased, that screw must have been wrenched on by a gorilla, either at S&W or at some police armory. The only way to get it out, to mount my LPA sight, was to drill it out.

I have another 5906 inbound, with the same Novak fixed sight. We'll see if that one is the same.

Well they do typically have Loctite on them, but I've never seen one that hard to remove. There are plenty of solvents that will take care of the thread locking compound but some might eat up the plastic plunger underneath the sight. Someone who's had to resort to that will have to give you advice. Getting the slide out of the dovetail itself is probably going to be the real challenge...the screw is a joke compared to that most of the time.

Thanks so much for your help, hopefully it will come out fairly easy. Knowing the size will help, I didn't think it would be a good idea to bring it to the hardware store.

You could also try applying a slight amount of heat to the sight which will make loktite turn loose also. If however there is plastic under it I don't know as that would be a very good idea. If however it is Delrin of the same makeup as bushing for shafts on textile machines it would probably be ok to use a small amount of heat.