what is a case "web"

Case Web: That part of the internal case where it transitions from the horizontal case bottom to the vertical case sidewall.

Cartridge Description

Good photo MEhavey. The web is a lot thicker. Hope i have this photo correct? Is there more than 4 types of headspacing? Something sticks in my mind there is 1 more?

"Headspace" originally referred to the very small gap between the bolt face and the bottom of a rimmed cartridge when fully seated into the chamber. Thin rims tended to leave more of a gap ("headspace") than thick rims (which if too thick, could interfere with the bolt closing/block sliding into place.) So you wanted "some" headspace, but not too much.

When modern rimless cases came into fashion, headspace took on a slightly different meaning: It now measured the much longer distance from the bolt face to a point about halfway up the case shoulder where it bends over from the sidewalls to the neck. Chambers are cut to this dimension ± a few thousandths. "Excessive headspace" means the chamber/bolt distance is cut too long -- and the cartridge has too much room to "rattle around."

That's the simple explanation of Headspace.

The "Web" of the case gets involved when the cartridge is fired. The firing pin pushes the cartridge to the forward limits of the chamber; the thinner forward portions of the case wall expands to lock the cartridge into place; and the case then stretches backward until stopped by the bolt face.

The thick web part doesn't stretch, however. Instead the wall just forward of that web stretches and the brass at that relatively narrow point (ring) gets thinner. Repeated resizing-then-firing w/ excessive headspace soon causes that streched ring area to fail.... which is bad.

Google "case head separation"

could you post some pics of these failures?

Click to expand...

See my photo link below

See the bright "ring" on the left, and an actual blowout/separation on the right:



When the left case is sectioned, you can see exactly how the "ring" has been thinned out ahead of the web.

Outstanding info!

Thanks!