CZ 457 chambering issue

[whiskey3]

Readers should note that it's impossible to know if a chamber or bore is "squeaky clean" by looking at it lengthwise from either end of the barrel. A borescope is necessary to make that determination.

Good point. I only say that because I worked at it until the swabs came out perfectly clean with solvent on them. I'd been shooting Super Colibris and this was likely the culprit. As a side note about the Colibris I noticed that they became quite spectacularly accurate after about 30 rounds; tiny groups at 25 yards vs shotgun pattern initially.