Twice in the last five years I have dealt with situations when what you imply is impossible has actually happened - drywall screws used to frame new stud walls have sheared and/or pulled out. In one case the building was subjected to sudden partial subsidence caused by an underground sewer collapsing, in the second case it was a jobber who hadn't sufficiently propped an RSJ which dropped (it went straight through the floor in fact because there was no pad to spread the load) and the stud wall upstairs ripped itself apart.I'm sure you are technically correct. However I have stud walls assembled with 75mm PB screws that have been up for years. They're not going to shear in a finished wall.
As foxhole says, particularly if you are a DIYer with a limited toolkit, a screw which isn't fully threaded is a better bet on softwoods. On 90 x 44mm (4 x 2in nominal) framing I'd be using something like these Goldscrews. (sorry, but for some reason the SFX site won't let me find 5 x 90 - the 5 x 80 look the same, and that's the link)Better not to have fully threaded screws as they pull in better, with full thread they can hold the timber apart if not firmly held.
Twice in the last five years I have dealt with situations when what you imply is impossible has actually happened
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