where does.40 S&W engage the chamber?

[bushmaster1313]

What keeps the rimless .40 from sliding forward further into the chamber?

 

[Dragon88]

The mouth of the case, that's where straight wall pistol cartridges headspace.

 

[bushmaster1313]

The mouth of the case, that's where straight wall pistol cartridges headspace.

Is that the forwad lip of the case that is a little wider in circumferance than the bullet?

What do you call the part of the chamber that it headspaces against?

 

[papajohn428]

I've heard it called several things, but I think most folks refer to it as a shelf or a ledge. It's just a section that hasn't been bored out quite as large as the back end of the chamber. It's also what makes a proper taper crimp a necessity with semi-auto pistol rounds. Apply too much crimp and the end of the case neck will travel too far forward, wedging the round in the chamber. If there's enough firing-pin travel, the round will fire but the case mouth can't properly expand to release the bullet, and your pressures skyrocket. That's what Jeff Cooper used to call a VBT, better known as a "Very Bad Thing".

 

[thndrchiken]

In rifles it is referred to as the throat, I'd imagine it's the same for pistols.

 

[WR Moore]

Actually, the "ledge" of the chamber on straight wall rimless chambers is called the shoulder. The throat is the section of barrel just ahead of the chamber, technically referred to as the leade.