barnbwt
member
- Joined
- Aug 14, 2011
- Messages
- 7,340
"^Ohh, that's good. I see. So higher pressure may make the case take longer to retract because of higher "adhesion" to the chamber wall. I didn't think of that."
It's not really a duration thing so much as a deformation thing. The high pressure on the interior "peens" the brass outward (the brass actually liquefies under pressure). Obviously, the brass does not change in volume, so the enormous surface pressure does not actually move the brass/chamber walls outward significantly, but the end result is the brass is larger than the chamber once removed. That's why re-chambering fired brass in high pressure cartridges is usually somewhat difficult; the brass is bulged outward slightly due to compression on the interior of the case walls caused by the high chamber pressures.
You end up with brass that's under compression on the inside, and under tension on the outside.
I would imagine the far bigger difference in FNX vs Glock performance would be the exact differences between the chambers (feed ramp geometry/etc. could probably effect how snug the round was wedged in there)
Another interesting question would be whether the barrel truly drops straight down or not; if it moves backward or even pivots on corner relative to the breech face as it cams down, it has to compress the chambered case a little. In a high-pressure cartridge where the expanded case causes residual tension after the pressure has dropped both radially and against the breechface, the slight forward motion of the breechface might result in a bind that saps the action of needed energy.
TCB
It's not really a duration thing so much as a deformation thing. The high pressure on the interior "peens" the brass outward (the brass actually liquefies under pressure). Obviously, the brass does not change in volume, so the enormous surface pressure does not actually move the brass/chamber walls outward significantly, but the end result is the brass is larger than the chamber once removed. That's why re-chambering fired brass in high pressure cartridges is usually somewhat difficult; the brass is bulged outward slightly due to compression on the interior of the case walls caused by the high chamber pressures.
You end up with brass that's under compression on the inside, and under tension on the outside.
I would imagine the far bigger difference in FNX vs Glock performance would be the exact differences between the chambers (feed ramp geometry/etc. could probably effect how snug the round was wedged in there)
Another interesting question would be whether the barrel truly drops straight down or not; if it moves backward or even pivots on corner relative to the breech face as it cams down, it has to compress the chambered case a little. In a high-pressure cartridge where the expanded case causes residual tension after the pressure has dropped both radially and against the breechface, the slight forward motion of the breechface might result in a bind that saps the action of needed energy.
TCB