.008 shoulder Bump?

[ajkellerusmc]

So Here I am resizing 2x fired Lapua .308 brass and to get the bolt to close without any resistance I have to get to where my #20 sinclair comparator tells me that I have bumped the shoulder a whole .008". I am confused as this has not happened to me before with this rifle and a few others. I have always bumped .002 and had the bolt easy to close on a resized piece of brass. If I screw the die all the way down over center and do a full resize I get .012" bump. When I acheive a .004 reading on the comparator I can see that the neck is only about 80% of the way resized, to me meaning the shoulder has not even contacted the die yet.

Pictures show what seems to be happening. The .008 and .012 cases chamber easily.

Particulars:

Brass Lapua 2x fired, deprimed cleaned and annealed, imperial resizing wax.

Redding premium resizing die with decapper and expander removed in a Harrells press.

Rifle is a Ruger american predator 18" (stock)

I am confused

 

[LaHunter]

I'm assuming your die is a FL bushing die?
How do you know that the shoulder is what is preventing the brass from fitting in your chamber and allowing a free bolt closing?
It could be your neck lengths or the body of the brass just forward of the base.
If a .002 bump has always allowed for an easy bolt closure and now it requires a .008 should bump, it could be an obstruction. Is your bolt face clean and free of debris? Do you have a bore scope to inspect your chamber?
Coloring your brass with a sharpie and chambering will give you an idea of where the excessive contact is being made.

 

[Black Hat]

I've sent myself demented doing exactly this one evening for my .243
I found the die and comparator was not contacting the shoulder at the same angle as the chamber.
I also found the case will grow in areas like the lower body and shoulder area before they size the shoulder fully.
Now I just size the cases untill they chamber with slight resistance and forget about the comparator for that rifle, it is a factory cut chamber.
On my custom barrels I have had no issues with bumping shoulder and measurement.

 

[ajkellerusmc]

I'm assuming your die is a FL bushing die?
How do you know that the shoulder is what is preventing the brass from fitting in your chamber and allowing a free bolt closing?
It could be your neck lengths or the body of the brass just forward of the base.
If a .002 bump has always allowed for an easy bolt closure and now it requires a .008 should bump, it could be an obstruction. Is your bolt face clean and free of debris? Do you have a bore scope to inspect your chamber?
Coloring your brass with a sharpie and chambering will give you an idea of where the excessive contact is being made.

The Die is not a bushing die, just a redding premium (black box) sizing die with all the guts removed. i do not know for a fact that it is the shoulder and not the base of the case. I will borescope the chamber after I clean it thoroughly.

 

[ajkellerusmc]

I've sent myself demented doing exactly this one evening for my .243
I found the die and comparator was not contacting the shoulder at the same angle as the chamber.
I also found the case will grow in areas like the lower body and shoulder area before they size the shoulder fully.
Now I just size the cases untill they chamber with slight resistance and forget about the comparator for that rifle, it is a factory cut chamber.
On my custom barrels I have had no issues with bumping shoulder and measurement.

Thanks for the input Black Hat,

I was thinking this is the way I will proceed, the same way we used to do it before we got all the fancy measuring equipment. My 338 lapua is a custom gun and the .002 bump has never been a problem.

 

[LaHunter]

How are you sizing the necks on a standard FL sizing die without the expander?

 

[ajkellerusmc]

How are you sizing the necks on a standard FL sizing die without the expander?

after all my brass prep is complete the last steps are to dry lube the neck and use an expander mandrell from 21st century to set the interference fit or as some would call neck tension. Last steps are powder and projectile.

 

[Alex Wheeler]

Get a different comparator, yours is measuring too close to the neck or shoulder and its picking up on diameter reduction as well as shoulder bump. Spin the case in the comparator you want to see it shine up the shoulder in the middle not close to the neck or shoulder.

 

[Bang4theBuck]

Be sure your necks aren't long too. If they are long, even after you bump the shoulder a few thousandths, if the necks are long you will get the same feel as if the base to datum on shoulder is long.

 

[Dean2]

First thing to check. Does the fired case, before you do anything to it, go back into the chamber and allow the bolt to close easily on it. My bet is they do as they are a prefect fire form to the chamber after firing. I will also bet that if you have a neck sizer die, just neck sizing the fired case will allow easy chambering of the neck sized but not loaded round. Whether you have a neck size die or not, the fact the fired case goes back in easily tells you the FL die is making something fatter or making the necks a lot longer as it FL resizes the case and you are effectively having to over resize it to get rid of that bulge, wherever it is being created. You need to find that spot and fix that issue because bumping the shoulder back .008 is just creating excess head space.

 

[misterc01]

One reason why I have two comparators - Hornady and Sinclair. They read different from each other, but consistent to themselves so I have two ways to see if something is amiss.

 

[ajkellerusmc]

Get a different comparator, yours is measuring too close to the neck or shoulder and its picking up on diameter reduction as well as shoulder bump. Spin the case in the comparator you want to see it shine up the shoulder in the middle not close to the neck or shoulder.

I spun a few cases on the comparator and the shiny spot is appearing at the base of the shoulder where it meets the body of the case, the angle of the case and comparator seem to be different.

 

[ajkellerusmc]

First thing to check. Does the fired case, before you do anything to it, go back into the chamber and allow the bolt to close easily on it. My bet is they do as they are a prefect fire form to the chamber after firing. I will also bet that if you have a neck sizer die, just neck sizing the fired case will allow easy chambering of the neck sized but not loaded round. Whether you have a neck size die or not, the fact the fired case goes back in easily tells you the FL die is making something fatter or making the necks a lot longer as it FL resizes the case and you are effectively having to over resize it to get rid of that bulge, wherever it is being created. You need to find that spot and fix that issue because bumping the shoulder back .008 is just creating excess head space.

The fired cases do chamber in the Rifle and the bolt does close easily. Case length is at the minimum still after resizing 2.005". Maybe I should try a different sizing die?

 

[Dean2]

The fired cases do chamber in the Rifle and the bolt does close easily. Case length is at the minimum still after resizing 2.005". Maybe I should try a different sizing die?

I would get a neck die, either a Lee Collet for a cheap way to try it out or a bushing die if you want to go full bore. Neck size a batch and check your groups, my bet is they will be as good or better than your over Full Length sized ones.
Why mess with a case that chambers easily, fits the gun well, and does not have excess headspace. Only thing you are sizing for is to get enough neck tension to hold the bullet. (I am well aware that neck sizing has gone out of fashion and not looking to start that argument, but for belted mags and many other hunting applications it is still a real good option.)