Question about function of a screw on barrel, under muzzle of SxS.

[NorthFork]

I have had the rammer on many sxs go forward on the first shot but never have they done as you suggest.
How many times has this happened to you?

Yes I agree. The position of the ramrod should have zero effect on the bullet or shot pattern.

As an aside, I have a ml that is old but not 'original' that has a ramrod that extends 5 or 6" beyond the muzzle. It has never effected the bullet pattern on target.

 

[Sparkitoff]

A lot of different Pedersoli/s have the screw. There's one on my 12 gauge and one on my 20 gauge. On a different shotgun that does not have a screw stop for the ramrod, I wrapped and epoxied a little spot on the rod so it is snug in the pipe. I did this the same way you'd wrap a fishing rod. By just building up that area slightly, the rod needs a little push to go in and pull out, but it stays put during firing and walking around hunting. Just the friction of that spot in the pipe keeps it put.