The sear rubbing on the bolt causes:
- wear on the top of the sear. It will eventually wear through the hardened surface. When this happens, it will change the timing of the mag such that it can possibly allow the on-off to let air past it before it should.
- wear on the edges of the bolt lip. This won't be as pronounced on the outer edge because the bolt rotates as you shoot, so the wear will be spread out all over the edge unlike the sear wear.
-However, because the sear is pressing up, as soon as the bolt gets back far enough, the sear tip will slide up past the front of the bolt lip. As it does this it will gradually wear away at both the sear tip and the front of the bolt lip. This will change the parameters of the bolt setup which will lead to leaking and full auto issues.
- friction - if you have a sensitive level 10 setup, additional friction on the movement of the bolt can affect the ability of the bolt to reset and could result in bolt stick in some instances.
Except for the Automag in front, its usually the man behind the equipment that counts.