[44 AMP]

I've been trying to wrap my head around the whole "firing pin drives the case forward" thing, and I keep coming back to a couple of points that don't seem to jibe. Speaking specifically of a rimless, non-belted bottle neck case and a push feed bolt system.

I agree that the base of the case will be a (small) distance off the bolt face when the firing pin strikes. What I don't get is where the "room" for the case to move forward comes from.

The front edge of the bolt pushes the case into the chamber as it feeds from the magazine. With many designs that front edge of the bolt is not the bolt face. When the case clears the magazine it pops up, up the slope of the feed ramp, and as it enters the chamber the base lines up with the bolt face, BUT at this point it is still the extractor and ejector that are touching the base of the case and pushing it forward. Not the bolt face itself.

This continues as the bolt closes, until something stops the case from moving forward. That "something" should be the shoulder of the chamber, but it could be the bullet jamming into the rifling. Either way, something stops the case from moving further forward, despite the continued pressure from the bolt.

So, the case is stopped, and the bolt continues to move forward a bit, until it reaches the end of its travel, at when point, the extractor has snapped over the case rim, and the spring loaded ejector is compressed.

This puts and keeps a forward pressure on the case, which is still very slightly "ahead" of the bolt face.
So, HOW does the case move back, against the tension from the ejector (and possibly the extractor) in order to create the clearance for the firing pin to drive it forward???

It's a demonstrated fact that if a chamber has been cut "too deep" for a case, (and there is no bullet jammed into the rifling) that the push feed will push the case ahead of the bolt, if the space exists to the point where the extractor does not snap over the rim and the firing pin does not reach the primer. It is the case being stopped from moving forward that makes the push feed work.

What force exists to push the case BACK against the bolt face BEFORE firing?? I can't think of any.

I do agree that the thinner case neck and shoulder seals to the chamber first when fired, and the case head gets pushed back by the pressure until the bolt face stops it, and that is why the case stretches.

But I just can't figure where this "drives the case forward comes from. Additionally, if it actually WAS happening that way, wouldn't the only available space for forward movement be the distance from the bolt face to the inner edge of the extractor claw, minus the thickness of the case rim??

A controlled round feed system doesn't need to rely on the chamber to stop the forward movement of the case during feeding, it is the rear face of the extractor that does that.

SO, if a push feed has room to drive the case forward with the firing pin strike, where does that room come from?? And if its not true, why are we talking so much about it???