There's an awful lot of right, wrong, and indifferent opinions going on, so let's see what the manual says.

From the Shield Safety & Instruction manual: Pull the slide to the rear and release it, allowing it to carry fully forward. This strips a cartridge from the magazine and seats it in the chamber of the barrel.

From the M&P Pistols Safety and Instruction manual: Pull the slide to the rear, press down on the slide stop to release the slide and allow it to carry fully forward. This strips a cartridge from the magazine and seats it in the chamber of the barrel.

So the sling shot is used for both, but on the M&P Pistols it actually says to do both at the same time. Is it the best or fastest, good question, but it is the recommended method straight from the manual. If it's recommended, I must assume S&W sees it as the safest method as well. You can play he said, she said all day, but if you follow what "we" said in the manual, there will never be a liability question, and firearms manufacturers are all about avoiding liability.

OP, it's up to what works for you. Good luck and good shooting.

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SFC, US Army, Retired