It is not the diameter of the brush, i.e. .22 caliber that is the problem, it is the length of the brush. The ejector port is very short on the MP5 and so if you push a longer brush down the barrel, it doesn't have enough room to go all of the way out into the ejector port, hence the brushes are facing the wrong way that are still in the barrel. In order to remove the brushes, you must now force the brushes against the rifling in the barrel to pull it back out, and this damages the barrel and the chamber. I have never owned a weapon where that is the case but I had to return my brand new MP5 because of this condition. I will never make that mistake again. As for the bore snake, it may be the brand of the snake or whatever, but the one that I have for my other .22 weapons won't even drop down the barrel to be pulled out. As a matter of fact, the original cable that I have with my Otis kit is too large in diameter and won't even fit into the chamber to properly clean the weapon. That is why I had to order the small caliber cable to go into the chamber and through the barrel. Hope this helps.