The 22cal rod doesn't fit my sig sauer mosquito 22, is it a different size? The 22cal rod does fit my smith&wesson mp 15-22. — 1 Answer

I can't find anything special written up about the Mossy's barrel or rifling profile, so it's probably normal stuff, not hexagonal or multi-groove. It seems the Mosquito was made by GSG for SIG so they could come in under a certain price point that SIGs are not normally known for, so that makes it double-normal. I would chalk this up to possibly leading in the barrel, or perhaps a slightly tapered barrel at the crown. This can happen to guns that have threaded barrels and someone threads something on it and pushes down a little too hard, shrinking the bore a tiny bit. Yes, it's a thing, especially on thinner barrel stock.