What caliber, what kind of magazine tube, what spring and basepad combo is it?
The nose dive problem in S_I mags is usually caused by a weak spring and/or a follower that is dragging on the inside of the tube. If the follower drags, figure out where the contact is and trim it a little at a time until it will go in and out with little to no resistance. There can be other factors like a slide speed that is too high (too light of a recoil spring) that doesn't give the round enough time to get all the way up in the magazine before the slide strips it out, but that's probably less likely.
This is 38supercomp. All parts are new. Tube is for EAA Witness. Will the top part of the mag make any difference? I mean if the top part where it holds the ammo is too tight, will that casue nose diving? It happens sometimes even on the first round.
I appreciate for all your advise.