Actually, it is not rare in 22 rimfire, though not as common as it once was, due to the current extreme rarity of squibs in current commercial ammo. in 22, it comes when a bullet fais to exit the bore and another is fired behind it. the second bullet doesn't (usually) actually touch the first as the air between them is violently compessed and starts the first moving again. Meanwhile, the peak in air pressure actually swells the barrel (usually only a matter of thousandths of an inch) BETWEEN the two bullets. Sometimes the accuracy goes completely to he!!, sometimes only halfway. Usually, it is possible to feel and/or see a smooth swelling on the outside of the barrel at the point.
crankshaft
paranoia is just fine when they actually are out to get You!
[This message has been edited by Juan Hunt Greer (edited September 11, 2000).]