I am planning on doing a screw build using a 1.6 mm receiver. Are there any issues concerning threading the trunnions after they have been  narrowed to 1.6mm receiver specs? Specifically, is there enough thickness left  after machining, for the screws to grip?

Thanks
CJ

i wouldnt try it
there isnt much there to begin with

but im not a fan of screw builds and prolly alittle bias but hey atleast im honest

I agree. There is only .100 of meat to start with, removing another .6mm (@.025) will leave you with only .075 to work with.

When using a 10-32 screw You'd be lucky to get 2 full threads

Yep +1 to all of the above.- Buy a Tapco flat and go "get bent" if you're determined to have a screw build.

Personally, I would not use a 1.6mm receiver for a screw build.  And that's from someone who does nothing but screw builds (and without removing the barrel.)  The rear trunion is a non-issue with the 1.6 receiver as there is beau coup metal to shave after emoving the rivets.  However, the 4 upper screws on the front trunnion will present a problem---even with the 1.0mm receiver there's not a lot of meat to tap the 10x32 screws.  The two lower screws on the front present less of a problem, especially if you use 1/4x28 button head screws, but the 4 uppers are the sticking point.  You don't want to tap into the barrel shank and if you have to shave the front trunnion to fit the wider receiver you make the issue more acute.  Better to shave the receiver, which kind of defeats its advantages.  Better yet to use a stock 1.0 receiver which was made to handle full auto fire which you will not experience except as the addicted bumper.

The screw build was my choice because of limited tools (drill press and taps) and the fact that you can really fine tune the fit of the mags and top cover.

HTH