That would be a standard atty barrel length - which is 22 mm. The stock 510 attys seldom deviate from that. (I have them right here - just got some. I measured even for you to check. lol)
They have to be a standard length or they wouldn't work with standardized 510 cartridges designed to fit in them. Ok, so not so many people using those cartridges with an atty any longer. But there would be no point in stock 510 attys deviating from a standardized length either after all these years. (More than you wanted to think about - I know...)
