The take down screw appears to be a #12-24 Low Head Socket Cap Screw. Its shaft is 0.210" which is a #12 screw thread. All black cap screws are commonly Grade 8 fasteners or stronger. I can't find the torque specs for this fastener but here is a torque chart for a #10 and a 1/4 inch which are the next bigger and smaller fasteners to a #12...
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Low Head Socket Cap Screws | Coburn-Myers
...Since the 1/4 screw torques to 77.9 in./lbs. and the #10 screw torques to 33.5 in./lbs., let's "assume" that the #12 cap screw torques between the two. I get around 56 in./lbs. by my calculations.
I have been torquing my take down screw to 40 in./lbs. and it never came loose. I just took my take down screw back out to help out here but it seemed to break away easier than usual. Since it has not been shot since I cleaned and reassembled the pistol, I've decided to increase the torque to 50 in./lbs.
Hope that helps.