I shot the NEI 349C extensively in my Shiloh business rifle when I first started shooting BP.  I too lubed the scraper groove so I am not sure that it did much scraping.  I shot quite a few 1-1/2” 200 yd groups at during practice and even won a 300 yd. sitting cross stick match at Tacoma one year with a 97 3x. It was my first ever win.   

Jack

If one assumes that the concept works and it catches and holds previous fouling in a groove, what is happening to the collected fouling as the bullet rotates down the barrel? And, of most impotance, at exit from the muzzle? Assuming rotational force keeps any collected fouling evenly distributed around the groove during barrel travel, what happens in exit? Is it flung off evenly? I don't know the answer, nor dare I posit one, but without knowing whether the fouling trapped in the groove is evenly distributed and ejected by the rotational force of the bullet on exiting the muzzle with no impact on stabilization and flight path, I would fear adding yet another variable to ballistics. Mind you, paper patched bullets have a scouting effect, to some extent, and they shed not just fouling, but their paper without horrific impact.

Since like Beckett, I seek simplicity and the removal of variables, I would probably be opposed to such a groove. But I must add that I am curmudgeonly, somewhat opposed to innovation, and only just getting comfortable with the hep-cat, new fangled use of that "smokeless" powder that seems all the rage. So my views on the matter may safely be discounted...

It is a wiper band that is in front of the first lube groove. It pushes everything in front of it down and out of the barrel so there is nothing to get into a groove. Size is basically 2 to 3 thousands give or take over the actual groove size.

Don't know if there is a benefit to it or not. The only bullet that I have with it is my 25 cal. 120 grain Mos.

When the minie bullet was being developed in the US for the new 58 caliber rifled muskets the grooves in the circumference of the bullets were intended to be scraper grooves to push fouling from the previous shot out the barrel thus enabling continuous firing. Apparently it worked fairly well. 
The lubed bullet had been developed a few years before by Richard Lawrence of Robbins and Lawrence for the Sharps percussion rifles to keep accuracy after more than a few shots.

JS, suggest you just add a lube groove in front, the scraper groove is pretty hard to fill with lube.   Mine wouldn't while pan-lubing.

A scraper groove has the front bore diameter or less, and the rear groove diameter.  Also the front usually is quite a bit tapered, which is what makes it hard for lube to stay in there.