Land marks on brass mouth?

[Hello123]

I noticed on the outside edge of the case mouth of my brass the imprint of the lands are present. Any thoughts. Can't imagine that the brass is long enough to touch the lands. The brass had been trimmed to length prior to use with a lee trimmer?

 

[Lavid2002]

Hmmmm LITERALLY an imprint?

As in the neck is pushed in in the form of the lands? Please give us a pic so we can better diagnose the situation.

 

[SDC]

What firearm make/model has your brass been fired in? A number of firearms use fluted chambers to ease extraction, and this may look like lands.

 

[Lavid2002]

Fluted barrel

A fluted barrel is SLIGHTLY fluted, confusing it with lands would be a remarkable mistake as there would be allot indentations that would have to be measured with a caliper, they would appear on the case walls I dont beleive they would show on the case neck. Anyways it would have allot of indentations rather than five or six left from the rifling lands.

 

[nitesite9]

Do the marks look like the ones in the middle case (never mind the split cases)?

Those are from firing in a fluted chamber.

 

[Hello123]

They look similar. When I get home I will post pics.

 

[Hawg]

I've got a 7MM Mauser that did that. Extraction was extremely difficult(had to beat it open). Cases had distinct rifling marks on the necks. I did a chamber cast and it was 7MM but the rifling continued into the neck of the chamber. I used a piece of emory cloth on a wood dowel in a drill, then used valve grinding compound to smooth it up. Works fine now and the marks are gone.

 

[Hello123]

That is kind of crazy to think that everytime a bullet is chambered it is already fully seated in the lands. I will have to study the chamber. It doesn't do it on every round.

 

[Master Blaster]

certain factory ammo in 5.56 has a crimp that appears as you describe.
A lee collet crimp die will also leave indentations in thre case mouth that look like lands.

 

[Hawg]

That is kind of crazy to think that everytime a bullet is chambered it is already fully seated in the lands.

Well it wont be. If they were that deep it wouldn't chamber. Mine weren't deep but they were noticable. Closing the bolt wasn't difficult but after it was fired and the brass flowed into the grooves extraction was a bugger. Unchambering loaded rounds didn't show any marks.

 

[Hello123]

This is a picture.

 

[nitesite9]

That is nothing more than factory neck crimping using a collet crimping die. If your case neck was actually jammed into the throat (so far that the rifling was cutting into the case) you would have overpressure problems like you cannot imagine.

A .223 Remington/5.56mm NATO chamber would have the case mouth set pretty far off where the lands begin, almost impossible for a case mouth to come near the throat.

Winchester and some other factory ammo makers crimp the case mouth like that, and it's far from being long enough to engage the rifling.

 

[Hello123]

master blaster and nitesite, you did turn the lights on. That was a mixed batch of brass now that I think about it. That was left over Winchester brass. Good job and thanks for the insight.