Building up a bolt completely from scratch parts, attempting to insert the safety selector into it's mating part, I can get the small plunger on the selector to move/compress with a small tool/driver but can't keep it depressed enough to slide it into it's mating groove...just not a lot of room to work with (in contrast inserting or removing a magazine cutoff is much easier...more room to work with).

Is there a special tool to do this (which of course I don't have!) or some other clever technique?? Thanks!

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I would think a small screw driver with a tapered blade would work, about 1/8 wide. Oil the plunger good and work it several times to get the lube in the internals. Slide the screw driver in till it compresses the plunger most of the way then install. The trick will be to have a small enough driver so as the plunger gets into the groove area before the driver blade stops the movement.
Lots of smart people here and a several of them have done it many times, they may have better methods or descriptions.

OK, thanks. Followed your suggestions, used jewelers driver & managed to finally get it. Was originally holding it all in my hands too but finally put the flat faces of the bolt sleeve in a vice (cushioned) to get max leverage on the selector & plunger, could never really get the plunger far enough in to just push the selector on by hand but got it close enough to tap gently with a rubber mallet & nudge it over the lip.

The project piece is on the right. Appreciate it!

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