If the idiots in charge just gave you the wrong ammo for what the rifle was designed for (which is one of the problems they had in Vietnam), or the rifle is just dirty because the idiots in charge didn’t give you a cleaning kit (another problem in Vietnam), then yeah, just whack the forward assist to get it properly into battery. But if you have a chamber obstruction or a bad round, you can end up making things a lot worse by brute-forcing it into place. No, you don’t want to stop and field strip it, but a better idea is to pull the charging handle back and take a look at what’s actually going on. Most likely, it’s not going to be something that the forward assist can fix.