"Breaches" is wrong; the singular is "breech",* the back end, not "breach" a breakthrough point. So the plural is "breeches." Since most shooters like the breech at their end of the gun, rather than the muzzle pointing at them, that kind of gun never did catch on.
* Yep, the same as the word for one's rear end and the source of the term "breeches", or "britches" for trousers which cover that anatomical feature.
Jim