Nobody checks in level 2s on down..I was at a match once where some guy was shooting Production with his Glock.. anyways he shot most stages till somebody asked him what barrel he was using.. apparently he had an aftermarket barrel..titanium parts, aftermarket springs all sorts of stuff.. his lame excuse was "oh I was praticing yesterday and forgot to take the parts off"...
Then youve got guys using some Production guns like CZ where youve got tons of factory parts.. Production division is modified depending upon which brand of gun you use...
Really though would some basic off the shelf barrel make any difference on a Glock? Might even be worse then factory....