6BR taper in neck

[Okumacaptain]

Brass is on 3rd firing , not annealed yet , and a .242 pin just barely starts and a .240 pin goes all the way . So there is about .002 taper in length of neck . Is this normal ? Is it due to not annealing ?

Thx

Mark

 

[rwj]

Sounds like there is a “donut” forming at the neck/shoulder junction… not uncommon and not a function of annealing.

 

[Okumacaptain]

Sounds like there is a “donut” forming at the neck/shoulder junction… not uncommon and not a function of annealing.

The taper is true from top to bottom . I figured with a donut the top 2/3 would be straight and then you hit the donut at neck shoulder junction ?

 

[Okumacaptain]

Sounds like there is a “donut” forming at the neck/shoulder junction… not uncommon and not a function of annealing.

So should I get a neck reamer ?

 

[rwj]

So should I get a neck reamer ?

Unless the bullet pressure ring is seated at/below the neck/shoulder junction, no action is required. If you feel compelled to do something, I would recommend using a mandrel to expand the ID thereby moving the donut material towards the OD, then perform a skim cut on the neck.

 

[rwj]

The taper is true from top to bottom . I figured with a donut the top 2/3 would be straight and then you hit the donut at neck shoulder junction ?

When firing, then resizing cases, it’s hard to predict how the material will be displaced...

 

[Okumacaptain]

When firing, then resizing cases, it’s hard to predict how the material will be displaced...

Gotcha ! Thank you

 

[AlNyhus]

Good catch....more people should check for this..... 'the funnel'. -Al

 

[AlNyhus]

Have you outside turned the necks? -Al

 

[Okumacaptain]

Have you outside turned the necks? -Al

Have not . It’s a .272 no turn neck .

 

[AlNyhus]

With fired and unsized cases/necks, the Wilson inside neck reamers for use with their trimmer is what I use. They will make them whatever diameter you want. For example, I have them from .3060 to .3080 in .0005 increments.
Be aware that the standard reamers are .002 over bullet diameter....hence the custom sizes. One at .2420 would be perfect for your situation.

Good shootin' -Al

 

[AlNyhus]

I should add that when doing this, it's critical to do it on fired cases right from the chamber. Doing it on a sized case/neck can cause the inner neck to not be parallel with the outer neck....bad JuJu for accuracy.

I don't have a picture handy of my setup but this is from Tony Boyer's book. He uses a chucking reamer and a machined guide bushing but you get the idea.

Good shootin' -Al

 

[Webster]

Brass is on 3rd firing , not annealed yet , and a .242 pin just barely starts and a .240 pin goes all the way . So there is about .002 taper in length of neck . Is this normal ? Is it due to not annealing ?

Thx

Mark

When you fire the case and maybe from sizing also brass flows from the shoulder into the neck. There may be a donut but there is brass flow into most of the neck. Proof increased thickness is beyond the donut is when you return the neck after many firings, brass is removed just about along the entire neck. You could probably measure it with a ball mike. All my rifles shoot under 1/2" for GH hunting. I don't get too OCD on details.

 

[gunsandgunsmithing]

Haven't seen it asked yet so I will...Will a bullet fit into a fired and unsized case?

 

[Okumacaptain]

Haven't seen it asked yet so I will...Will a bullet fit into a fired and unsized case?

Yes it does . Actual fired case mouth measures .2445

 

[Okumacaptain]

When you fire the case and maybe from sizing also brass flows from the shoulder into the neck. There may be a donut but there is brass flow into most of the neck. Proof increased thickness is beyond the donut is when you return the neck after many firings, brass is removed just about along the entire neck. You could probably measure it with a ball mike. All my rifles shoot under 1/2" for GH hunting. I don't get too OCD on details.

I shoot F open against some very good competition so I need to be a little OCD

 

[gunsandgunsmithing]

Yes it does . Actual fired case mouth measures .2445

Something is wrong here. No offense, but your measuring appears to be off if a 242 pin just starts, yet a .243+ bullet goes in. Am I missing something?

 

[Okumacaptain]

Something is wrong here. No offense, but your measuring appears to be off if a 242 pin just starts, yet a .243+ bullet goes in. Am I missing something?

Fired case mouth measures .2445 ! Sized case mouth .242 starts and a .24 goes all the way through .

 

[gunsandgunsmithing]

Fired case mouth measures .2445 ! Sized case mouth .242 starts and a .24 goes all the way through .

So it's happening during the sizing operation? If you have pins that are a tad bigger, what do they do in a fired piece of brass, eliminating the sizing operation, the od should be straight, or as straight as the chamber. What happens with roughly a .245ish pin and a couple +/- of whatever just fits in the fired case?
edit....2445. Does the fired case have the taper, too?
fwiw, I get a distinct bell mouth when I neck from 6.5 to 6mm for a 6 Grendel but it completely goes away after the first firing.

 

[Okumacaptain]

So it's happening during the sizing operation? If you have pins that are a tad bigger, what do they do in a fired piece of brass, eliminating the sizing operation, the od should be straight, or as straight as the chamber. What happens with roughly a .245ish pin and a couple +/- of whatever just fits in the fired case?
edit....2445. Does the fired case have the taper, too?
fwiw, I get a distinct bell mouth when I neck from 6.5 to 6mm for a 6 Grendel but it completely goes away after the first firing.

Good point ! I haven’t checked to see if fired cases have taper . I’ve got some out in truck . I’ll check and get back with you .