Headspacing on the shoulder on a belted case

[Dodge61]

First of all can you and how do you make sure that your reloads are headspaced on the shoulder instead of the belt of a belted magnum case. Particularly the 300 Win. mag. The Speer reloading manual suggests this, and I'm not exactly sure of how to be assured I'm doing it correctly.I think some folks turn the belt off of the case but I don't want to do this if I don't have to. Thanks for any assistance.

 

[JayIdaho]

I do it by measuring over a small bushing held against the shoulder of the case. The bushing is flat on one end, has a hole bigger than the neck and has an angle surface that matches the case shoulder on the other end. You can measure a case from base to the end of the bushing and determine the amount of shoulder setback that you are getting, adjust the die accordingly.
I think that RCBS makes a "case micrometer" or something like that that directly measures a case that is put into the device.

 

[DennisSorensen]

A shoulder bump gauge as Jay described is probably the most accurate way of doing it... you will be able to measure exactly how much you bump the shoulder.

You can get close to this by backing the full length sizing die away from the shell holder by one turn or more ... size a fired brass and try it in your rifle with the firing pin assembly removed. If there is a plunger ejector in the bolt face remove it too.. this is so you can feel the bolt close on the case better. This partially sized case should be felt on closing the bolt. The bolt handle should fall closed on an empty chamber. Sometimes this method of sizing can cause the bolt to be quite hard to close. Move the die down slightly in the press and size that case again and try it again... until you can close the bolt easily but still feel the case crush a bit at the bottom of the bolt throw.

The reason a partially sized case done in a full length sizing die can be hard to close the bolt on, is the shoulder has bulged slightly convex as the shoulder diameter and neck diameter have been sized down. Lowering the die and resizing until this convex shoulder is flattened again is what you are feeling...

 

[Preacher]

The simplest way to check that is to light a candle, hold the case shoulder over the flame until it's covered with soot and insert it in your chamber, close the bolt and when it's retracted the case should show marks on the shoulder where it contacted the front of the chamber.
You can feel this much better if you remove the firing pin assembly before doing it...
Keep adjusting the die until the case shows the marks on the shoulder, and you'll be OK...........
Ideally a empty bolt will fall of it's own weight, and then fall about halfway down when a case is inserted if the headspace is correct...;;.
No marks on the shoulder mean a headspace problem.

 

[Dodge61]

Thanks to everyone for the useful info. It is greatly appreciated.
Dodge61

 

[REELDOC]

An RCBS precision mic takes all the guess work out.

 

[eddyverhoeven]

The simplest way to check that is to light a candle, hold the case shoulder over the flame until it's covered with soot and insert it in your chamber, close the bolt and when it's retracted the case should show marks on the shoulder where it contacted the front of the chamber.
You can feel this much better if you remove the firing pin assembly before doing it...
Keep adjusting the die until the case shows the marks on the shoulder, and you'll be OK...........
Ideally a empty bolt will fall of it's own weight, and then fall about halfway down when a case is inserted if the headspace is correct...;;.
No marks on the shoulder mean a headspace problem.

Hi preacher, how are you doing?

A friend of mine uses the same method and it's the old machinists' method. Time consuming? yes, some but can't beat his precision in chamber fitting his brass,300 Winchester mag.)

Ed

 

[CatShooter]

All new cases have some "headspace"... it is allowed for in the SAAMI specs.
If there were no allowed for headspace, you could never afford cases made to "0" headspace, and most new ammo would not fit inthe chambers.

When ANY bottle neck cartridge is fired, the case blows out to fill the chamber - after that,assuming no dumb actions on the part of the loader), the cases has approximately ~ "0" headspace, or as close to it as it will get.

The belted cases usually have less headspace error than the shoulder on new unbelted cases...

Don't worry, be happy!!


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