Neck diameter confusion

[BeefyT11]

Hey fellas,
Im planning on sending my 6.5 creed Forster die to them to have the neck honed. Brass is annealed after every firing.
The issue I'm running into is this, Forster tells me their neck are of their die is honed .285 from the factory, when sizing brass without expanding the neck, I should be achieving an outside neck diameter of .286 after springback correct? Every one of my sized pieces measures .283. I'm not sure what is causing these necks to be over sizing, thoughts? The only thing I can come up with is lube buildup in the neck area.
Any help would be appreciated
Beef

 

[AJC]

The spec only has a negative value. That way it always oversized and the expander pulls it back to spec.

 

[243winxb]

Is fired brass being sized down more then .008" ?

 

[jepp2]

I'm not sure what is causing these necks to be over sizing, thoughts?

The die neck is smaller. Easy enough to check. You can use a pin gage, or if you don't have any, take a pure lead (sinker but hard to find pure lead, muzzleloader balls are easy to find) and use the proper size oak dowel to force it through the die neck. Just like slugging a bore on handgun. Then measure the slug. Don't forget to oil the die neck before slugging.

 

[BeefyT11]

Is fired brass being sized down more then .008" ?

Yes, loaded round outside neck diameter is .291, after annealing and sizing outside neck diameter is .283

 

[243winxb]

It happens with bushings too. Redding info.

It has come to our attention through customer calls and our own use of the bushing style sizing dies that in certain instances, a given neck sizing bushing will produce a case neck diameter that can be several thousandths of an inch smaller than the actual diameter of the bushing. This idiosyncrasy occurs when the neck diameter of the fired case is a great deal larger than the diameter of the neck sizing bushing, such as occurs when factory chambers are on the large side of the tolerance range and the brass is on the thin side. Typically, we have not noticed any problems until the case neck is reduced more than 0.008-0.010".

https://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection

 

[Dusty Stevens]

A bushing die with no expander would solve your extreme oversizing issue

 

[JFrank]

Yes, loaded round outside neck diameter is .291, after annealing and sizing outside neck diameter is .283

You removed the expander ball and now see how much they really under size.
Either put the expander back in and stop measuring or get a bushing die that doesn’t use that system.
Someone with pictures and diagrams will be along shortly.
J

 

[AJC]

This die is the same one I bought and intended to do exactly what your doing. There was a short article on this sight about having two or three dies vise bushings and it possibly being better and cheaper. I dont have the experience to make any such claim but I went this route and planned to use a mandrel set for final bullet tension/hold. I believe both ways work and should produce equal quality. Getting the die close so your not overworking the brass would be a great goal imo.

 

[BeefyT11]

This die is the same one I bought and intended to do exactly what your doing. There was a short article on this sight about having two or three dies vise bushings and it possibly being better and cheaper. I dont have the experience to make any such claim but I went this route and planned to use a mandrel set for final bullet tension/hold. I believe both ways work and should produce equal quality. Getting the die close so your not overworking the brass would be a great goal imo.

That's my goal as well to set final neck tension with a mandrel, just looking for some insight so I dont over due the honing. My math wasn't adding up and I couldn't understand why

 

[AJC]

That's my goal as well to set final neck tension with a mandrel, just looking for some insight so I dont over due the honing. My math wasn't adding up and I couldn't understand why

Loaded round minus neck tension minus spring back.

 

[nmkid]

Couldn't he also chuck the expander in a drill press, use emery cloth to size down the expander until he gets the desired tension?

 

[AJC]

Couldn't he also chuck the expander in a drill press, use emery cloth to size down the expander until he gets the desired tension?

The goal is to reduce working the brass. Not achieving a final dimension.

 

[BeefyT11]

The goal is to reduce working the brass. Not achieving a final dimension.

Yes

 

[BeefyT11]

It happens with bushings too. Redding info. https://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection

Fired brass neck diameter is .295", so if what Forster told me (die neck diameter is .285") is actually correct I'm sizing the neck .010" and fall into that niche that was described in the article you posted. I wonder if having them open up the neck to .288" would be enough to allow the brass to size properly and leave me with a neck diameter of around .289" after springback?

 

[hogpatrol]

What measuring instrument are you using? Calipers or micrometers? Honing that much out of the die, the neck surface may very well be soft. Are they going to send it to the oven again? Harden it and then draw it back?
Your best approach is Redding type S or other brand that uses bushings and no expander ball.

 

[gunnermhr]

Your best approach is Redding type S or other brand that uses bushings and no expander ball.

Sell it and buy a bushing die, you will never regret it

 

[BeefyT11]

What measuring instrument are you using? Calipers or micrometers? Honing that much out of the die, the neck surface may very well be soft. Are they going to send it to the oven again? Harden it and then draw it back?
Your best approach is Redding type S or other brand that uses bushings and no expander ball.

CUSTOM NECK HONING OF FORSTER FULL LENGTH SIZING OR NECK SIZING DIE
We custom-hone the inside neck diameter by using a diamond stoning process. We enlarge the inside diameter to your specification to prevent over-sizing of the case neck due to thick neck walls. You may require this service for multiple reasons:

1. If you use some brands of brass cases which have thicker neck walls.
2. If you do not intend to outside neck turn case necks that have thickened after repeated firings.

Please specify the inside neck diameter. Note:

1. No more than .008″ stock removal from your existing die neck diameter is possible.
2. Honing is done in increments of one-half thousandth of an inch (.0005″), meaning that your specified inside diameter must be either.XXX0″ or .XXX5″.

That's the service Forster provides, I would be taking .003" out, I'm using a set of calipers, and accept that they aren't the perfect tool for the job, but believe they are adequate.

 

[Dusty Stevens]

Hope you hit it exact and thats the right tension you need and hope you never have to get different brass.

 

[hogpatrol]

Hope you hit it exact and thats the right tension you need and hope you never have to get different brass.

Which brings us to another question, what brand of brass are you using to get these dimensions. Yes, calipers are good for ballpark numbers, not so good for anything requiring precision.