Seating Depth - Thinking Outside the Box

[AlNyhus]

Your logic is somewhat right but there is also some amount of brass flow with multiple firing/sizing ops that ends up at the neck/shoulder junction, creating a bit of a donut. But yeah, necking up creates a healthy donut due to the brass that becomes the lower portion of the neck came from the shoulder, which is typically thicker. Bottom line, while not often severe, slight donuts can occur without necking up.

Yep. That brass has to go somewhere! -Al

 

[dellet]

Your logic is somewhat right but there is also some amount of brass flow with multiple firing/sizing ops that ends up at the neck/shoulder junction, creating a bit of a donut. But yeah, necking up creates a healthy donut due to the brass that becomes the lower portion of the neck came from the shoulder, which is typically thicker. Bottom line, while not often severe, slight donuts can occur without necking up.

I’m think a lot of people would surprised if the would seat a bullet with enough bearing surface to be below the shoulder, above the mouth, and measure the neck diameter top center and bottom. The amount of taper is sometimes a bit frightening.

It would sell a few neck turning tools I’m sure.

 

[urbanrifleman]

"The only real way to fix the donut is don't be near it"

A famous shooter I know said that.

I think for average folks, who don't want to turn necks and add all sorts of other steps, that is true. In fact, being a long way from the donut fixes a lot of issues, from my experience.

 

[Bc'z]

"The only real way to fix the donut is don't be near it"

A famous shooter I know said that.

I think for average folks, who don't want to turn necks and add all sorts of other steps, that is true. In fact, being a long way from the donut fixes a lot of issues, from my experience.

Agreed but in some instances as I posted above, due to magazine restrictions, case neck length and projectile chosen staying above the junction isn't possible.

 

[urbanrifleman]

Agreed but in some instances as I posted above, due to magazine restrictions, case neck length and projectile chosen staying above the junction isn't possible.

I that case, like back when I shot 243, I only sized half the neck

 

[Bc'z]

I that case, like back when I shot 243, I only sized half the neck

Neck sizer. lol
Absolutely, also the benefit of using bushing dies vs standard FL die.

In my case I only have a set of Hornady FL dies and I'm not particularly enthusiastic about spending $300 for a set of Redding with bushings.
Micrometer seater of course

 

[Doom]

The neck/shoulder junction moves forward when the case is fired. It moves backward when the case is sized. That “accordion”motion causes some buildup between.

I would suggest you learn how the case reforms when fired and resized.

 

[jds holler]

So my buddy and I shot together yesterday, and he had decided to go back to neck sizing "like he used to do" with his 8mm Mag.
I happened to look over, and he was using the 2x4 method of opening his bolt. His neck sized ammo wasn't working in about three different ways, and he finally gave up and decided to pull them down and start over. jd

 

[Clancy]

I would suggest you learn how the case reforms when fired and resized.

Clearly, you’re an idiot.

Forward upon firing. Rearward upon sizing. There’s no arguing that.

Ignorance is bliss though, so enjoy it.

 

[gunsandgunsmithing]

Clearly, you’re an idiot.

Forward upon firing. Rearward upon sizing. There’s no arguing that.

Ignorance is bliss though, so enjoy it.

You're just looking at things from a different perspective, I think.
When brass is fired, it expands and when it's sized, it gets squeezed down and that brass has to go somewhere. It does NOT go right back where it came from. Instead, it simply flows forward to a "stopping point", which is created by the relatively sharp radius change at the neck/shoulder junction...and creates a donut there.
But a say .020 wide donut that is maybe .002 thick, does not get pushed away by bumping the shoulder back say .002 and it doesn't just go away nor go back where it came from. To do that would mean that when you stretch metal in a car crash.. and then flatten it back out, the metal just went back together like it was before, but that's just not how it works. That would put a big damper on the Bondo industry. Lol! hope this clears it up better.

 

[gunsandgunsmithing]

I’m think a lot of people would surprised if the would seat a bullet with enough bearing surface to be below the shoulder, above the mouth, and measure the neck diameter top center and bottom. The amount of taper is sometimes a bit frightening.

It would sell a few neck turning tools I’m sure.

I know you are right but that's also another reason not to seat that far into the neck or to have enough clearance that it doesn't become an issue. I do agree with you though. Some chambers are even tapered in the neck, too....but not many/any BR type chambers that I'm aware of.

 

[Clancy]

You're just looking at things from a different perspective, I think.
When brass is fired, it expands and when it's sized, it gets squeezed down and that brass has to go somewhere. It does NOT go right back where it came from. Instead, it simply flows forward to a "stopping point", which is created by the relatively sharp radius change at the neck/shoulder junction...and creates a donut there.
But a say .020 wide donut that is maybe .002 thick, does not get pushed away by bumping the shoulder back say .002 and it doesn't just go away nor go back where it came from. To do that would mean that when you stretch metal in a car crash.. and then flatten it back out, the metal just went back together like it was before, but that's just not how it works. That would put a big damper on the Bondo industry. Lol! hope this clears it up better.

Mike,

I’m the one that said you could form a donut by just firing and sizing brass…. This “Doom” guy said I didn’t know what I was talking about.

Not sure why he came at me like that.
But if he really thought about it, firing and sizing IS necking brass up and down- just on a real small scale .

 

[Coyotefurharvester]

Brass gets the shoulder/neck pulled forward by the mass of the bullet(before neck releases) as the base moves rearward to the bolt face. Why sizing die must be set correctly (minimize the stretching in between- case head separation). And brass oal length must not interfere with the release of the bullet(pressure spikes). My over simplified take on brass prep.

 

[gunsandgunsmithing]

Brass gets the shoulder/neck pulled forward by the mass of the bullet(before neck releases) as the base moves rearward to the bolt face. Why sizing die must be set correctly (minimize the stretching in between- case head separation). And brass oal length must not interfere with the release of the bullet(pressure spikes). My over simplified take on brass prep.

Sorry, I sure didn't mean to step on any toes at all. Probably just me misreading something. I do that sometimes. Getting old ain't for the young!

 

[ELR LVR]

If your not necking up brass how does a donut form? With my 7saum hunting rifle(and my 30TC) bullet base is usually down below the neck well into shoulder, unavoidable with heavies or solid copper bullets in mags.

With some cartridges, when necking "DOWN" & Shortening.
The brass is thicker more toward the rear
and when necked down, the rear portion of the neck is thicker
also creating a donut, ID will be less toward the rear of the neck
Since the brass will be squeezed toward the inside

 

[Coyotefurharvester]

M.E. I'm not feeling any pain, just my thoughts outside the box on seating depth. Case manipulation in general. Not a competitive shooter, cheap hack it yourself guy who likes to read and probably talk to much.

 

[gunsandgunsmithing]

With some cartridges, when necking "DOWN", Shortening etc
The brass is thicker more toward the rear
and when necked down, the rear portion of the neck is thicker
also creating a donut, ID will be less toward the rear of the neck
Since the brass will be squeezed toward the inside

Nah...unless you lost me entirely.
As a rule though...the shoulder becomes part of the neck when you neck a case UP, not down. That's because the shoulder brass is typically a bit thicker than neck brass and necking up...the brass has top come from somewhere, right? Sure, there might be exceptions to that, but I've never seen it. Still, possible, though, I suppose.
I'm not speaking theoretically but strictly from experience. as well as just logic. So yes, I guess what you said is possible in theory but I've just never seen it, nor would it make sense...over a bunch of different wildcat examples...fwiw.

Often times, just doing something trumps whatever it is we might rationalize.

 

[ELR LVR]

Nah...unless you lost me entirely.
As a rule though...the shoulder becomes part of the neck when you neck a case UP, not down. That's because the shoulder brass is typically a bit thicker than neck brass and necking up...the brass has top come from somewhere, right? Sure, there might be exceptions to that, but I've never seen it. Still, possible, though, I suppose.
I'm not speaking theoretically but strictly from experience. as well as just logic. So yes, I guess what you said is possible in theory but I've just never seen it, nor would it make sense...over a bunch of different wildcat examples...fwiw.

Often times, just doing something trumps whatever it is we might rationalize.

Well it probably doesnt happen much anymore with brass availability, but cases like the 22 BR originated from the 308 case.

 

[gunsandgunsmithing]

Well it probably doesnt happen much anymore with brass availability, but cases like the 22 BR originated from the 308 case.

I'm with ya now. Case forming is a different animal from simply necking up a case though. I was referring to necking up, a case like a 6br to 30br etc. Of course the brass is thicker if you shorten the case.

 

[dellet]

I'm with ya now. Case forming is a different animal from simply necking up a case though. I was referring to necking up, a case like a 6br to 30br etc. Of course the brass is thicker if you shorten the case.

Where I have seen it happen is when a wildcat gains enough popularity to be commercially produced and the original cartridge has become obsolete. Have seen it a couple times.
Where I specifically ran into a problem was using 280 Remington brass for 270 Winchester. The neck is shorter on the 280 so necking down to 270 was a problem. Technically this would be reforming more than simply necking down, but it gave a memorable lesson.