I think most POI shift,resulting from a sling,is caused from a twisting motion. More of a sideways springing of the barrel channel,that induces side to side pressure upon the barrel.
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<br>POI can also shift,when using a bipod. That especially on a "floated" barrel(that is barely floated),that is housed within a fairly flimsy stock. It is easy to spring the stock upwards,causing vertical stringing.
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<br>So I think much depends upon the integrity of the stock in question,the bedding process used and what is used as a support/field rest(be it a sling,bipod,shooting sticks,etc,etc).
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<br>I would expect the test that you did,to cause lesser degrees of POI shift,as the forend is simply pulled away from the barrel,rather than pushing the barrel itself upwards or sideways.
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<br>Be curious to see how many clicks it took to skew a pre-established POI,when incorporating the front swivel stud and an anchor point that pulled sideways on the stock(45 degree angle or so),as opposed to 90 degrees down.
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<br>Thoughts?..................
