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Old 12-09-2004, 02:19   #96
Senior Member
Join Date: Dec 2004
Location: Pine Bluff, AR
Posts: 130
Re: Re: blowback vs fixed breech

Originally posted by philkryder

You're saying that there is sufficient pressure to tear a hole in a case -??but not sufficent pressure to push a bullet out of the barrel??

So are you talking about a case that is weakened to start with?
Or are you saying that this happens with a perfectly good case, due to the Glock design?

Are you also saying that AFTER the bullet leaves the barrel there is pressure that moves the slide?
yes to number one. it is easier to tear a hole in weakened brass than it is to push the bullet out of the barrel. but what is important here is that gas begins to leak from the hole, taking away from the pressure needed to propel the bullet forward.

to number 2- the case has to be faulty or weak to begin with. the enlarged part of the chamber in glocks can allow this to happen, i had a full auto m-11 that bulged the rear of the brass also.

to number 3, yes, the shell casing begins moving when the shell is fired, but moves mostly when the bullet leaves the barrel. think about it, if the casing exited immediately upon firing, what would the pressure behind the bullet have to push against in order to propel itself forward? if you look at a profile of most autoloaders you see that the barrel tilts when the slide is cycled. if the bullet moved slower, or at the same speed of the rearward-moving casing, then the bullet would fire high every time. i don't know the difference between blowback and delayed blowback, i'll have to look into that one.
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