Excessive shoulder setback

[rsbhunter]

Built a Savage target action with 6mm BR Norma Dasher. I know I'm not using the correct tool, but using a Hornady comparator insert in 30cal. Using this, the measurement to the point on the neck is .006-.007 longer than a cased sized to allow easy bolt closure. I know the suggested is.002 setback, and I don't want to overwork the brass..Using a Forster FL sizing die with the neck honed to size the neck -.002. I'm sure it's my mistake, what am I doing wrong? Thanks,rsbhunter

 

[Fast14riot]

Try using a 9mm case as a comparator, it is closer to the actual datum measurement. Just use the same case every time.

 

[rsbhunter]

Fast14riot, life must be so easy for smart people...that works SO much better..Using the 9mm case, I get .0015 to .002 difference. Thank you, this is why I post here, the information is always spot on....again, Thanks, rsbhunter

 

[BenPerfected]

To hone in on a consistent shoulder set back. Look at he bump collars

 

[rsbhunter]

BenPerfected, I think I need to get the correct tool to measure the setback, then if I'm not getting consistent measurements, I'll look into the bump bushings....just appreciate all the excellent info...thanks,rsbhunter

 

[Straightshooter1]

I've found the RCBS Precision Mic really easy and fast for checking the shoulders:

https://www.amazon.com/dp/B0767CSDMD/?tag=accuratescom-20

 

[Bob3700]

BenPerfected, I think I need to get the correct tool to measure the setback, then if I'm not getting consistent measurements, I'll look into the bump bushings....just appreciate all the excellent info...thanks,rsbhunter

Now that you have the tools to measure the bump accurately, realize that the type and amount of case lube will affect your setback dimension.

As you size, take sample measurements on the set back to make sure it stays consistent.

Bob

 

[dmoran]

This is my setup for measuring case headspace/shoulder bump:



A barrel stub with the chamber reamer ran in to near the body (often referred to as a "gizzy").
iGaging 2" stroke Dial Indicator with a flat contact point (model# 35-700-B50).

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[rsbhunter]

Bob3700, I use the 99% alcohol and lanolin mixture, place them in a Ziploc bag , spray and shake (gently). I'm sure there is some variance in the thickness, but try to keep it the same....what diameter Hornady headspace comparator insert would I use for 6mm Dasher ? Thanks for the help, I'm learning a whole new side of precision reloading...rsbhunter

 

[Webster]

This is my setup for measuring case headspace/shoulder bump:

View attachment 1145486

A barrel stub with the chamber reamer ran in to near the body (often referred to as a "gizzy").
iGaging 2" stroke Dial Indicator with a flat contact point (model# 35-700-B50).

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Nice setup. I noticed on a few blue prints I looked at that they give a datum base to shoulder to the middle of the shoulder. This is not a case dimension so I assume it's considered the proper place for the jump gauge diameter to rest.

 

[K22]

Try Imperial Sizing Wax - a tin will last you a long, long time - just finished up a tin I purchased in 2013 - I reload about 1000 to 1200 rounds a year. I apply sparingly with fingers and thumb standing them in Sinclair lube rack. Wipe off with a paper towel.

 

[Fast14riot]

Nice setup. I noticed on a few blue prints I looked at that they give a datum base to shoulder to the middle of the shoulder. This is not a case dimension so I assume it's considered the proper place for the jump gauge diameter to rest.

The datum diameter for the 6br is 8.88mm, which is why I suggested a 9mm case, it's close to the datum size and gives a better reading.

 

[rsbhunter]

I have used the Imperial sizing wax and liked it a lot.....I like the mix I'm using now, when I'm done sizing, all I do is wipe the cases with a cloth...hands aren't greasy or oily like the Imperial. And it (lanolin/alcohol) is working great, and costs pennies for how many cases it does....I really appreciate all the help and advice you all have given...Thanks again,rsbhunter

 

[Fast14riot]

Fast14riot, life must be so easy for smart people...that works SO much better..Using the 9mm case, I get .0015 to .002 difference. Thank you, this is why I post here, the information is always spot on....again, Thanks, rsbhunter

Just be sure to deprime the 9mm case so it doesn't rock on the primer against the calipers. The correct Hornady headspace comparator should be "C" 0.375" diameter.

Edited: comparator I originally said as B is for straight 6br, not Dasher, with the 40° shoulder, "C" should be used 0.375" diameter, based on PTG Dasher print.

 

[rsbhunter]

Fast14riot, you just saved me $11.00....was going to order the .350 one for 6br, didn't think about the shoulder angle change...thanks again...rsbhunter

 

[Dusty Stevens]

Get the whole kit. It comes with most youll ever need

 

[rsbhunter]

Thought about doing that..would be cheaper in the end....the 9mm case trick actually showed me what I was looking for....I had been measuring at the wrong point on the shoulder...once I did it correctly, my measurement was right where it should be....Thanks for the help and education....promise to file the information away for future use....rsbhunter