Nope you don't have to slank them in really far into the tube or anything, it pinches the end part of your thumb, the part (if you have trimmed nails) right at the end of your thumbnail.
Well, I always push them in over half way, then use the other shell to push it in, and so forth. Then, the last one, that's pushed in by my thumb... No pinches so far... And that' a lot of spring tension on that last one... Try opening the magazine tube with 7 shells in it.... Rocket attack.... Ha ha ha....