Re: 7.7 Jap misfire
Crap inside the bolt is correct.
As far as firing pins shortening, the steel firing pin should not shorten from a lifetime of impacting the softer brass primer. The reason a rimfire firing pin might shorten is because it is being peened down by dryfiring. The rimfire pin will hit the barrel face on most older .22's if no cartridge case is in the chamber. Hence, the popular use of snapcaps or fired .22 cartridges when practice firing. Note that many newer .22's have a firing pin stop that allows dryfiring without the firing pin hitting the breechface.
Of course, centerfire firing pins do not have that particular problem. Most centerfires can be dryfired without problems, with the notable exceptions of those designs that are subject to firing pin breakage.
The autonomic nervous system provides for involuntary muscle function - the work of breathing, digestion, and so forth. On some folks, that's a pure waste of ingenuity.