[headstamp]

Odd.

Rimless cases are supposed to headspace on their mouths when chambered. This sounds like the case mouth isn't and the bullet itself is headspacing the round when it hits the start of the rifling.

OR

Is it the action of the round being slammed home in the chamber and the delay in the bullet's inertia allowing it to be pushed a bit deeper in the case while the case moves into the chamber every time it happens?

OR

I would think the bullet would be pulled out of the case as the case mouth contacts the step in the chamber. Like the way a kinetic bullet puller works.

Just theorizing.

[ExpatGator]

Great minds think alike?

See my post in #10.

[ctdonath2]

Methinks it has more to do with the steep feed ramp affecting seating.

[tacticalogic]

Is it the action of the round being slammed home in the chamber and the delay in the bullet's inertia allowing it to be pushed a bit deeper in the case while the case moves into the chamber every time it happens?

OR

I would think the bullet would be pulled out of the case as the case mouth contacts the step in the chamber. Like the way a kinetic bullet puller works.

And are we talking about a round chambered from the clip by cycling the bolt, or inserting it directly into the chamber and then dropping the bold on it to keep a full mag? It seems the physics would be different for a round already in the chamber than one being stripped out of the clip.

[Double Tap]

There is no need to theorize. Bullet setback is a well known problem with pistols.

The bullet slamming into the feedramp as it is being chambered is what causes it.