We just read on WTA that there has been another KB with a Semi-Auto .17HMR rifle.  Most of the time the result of a KB is only stings and scares… but this time the shooter was hurt badly.

A blow back semi auto .17HMR (and even the .17 Mach 2 but to a lesser extent) is a bad idea.  No matter who makes the gun or how custom the gun is…. it’s going to, at some point, have a KB.  This is the same problem with EVERY semi auto .17.   Which is why all of them have been recalled and dropped from production by everyone that has ever made them.  Except for Alexander Arms, who is making a 1200 dollar AR type – that will still do the same thing everyone else’s did.   Even in one of the Gun Rags, during the review process the writer mentioned this happening but kept shooting it.
There are a couple causes of the .17 Rimfire KB’s.
1.  The bolt, rebounding off of firing the last round, slams forward into the cartridge rim hard enough to set it off while the round is in the magazine.
2.  A few rounds fires slightly out of battery puts enough carbon fouling in the chamber to builds up until a case is completely unsupported and firing pressure blows it.
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