Partially size body with no shoulder bump? Possible?

[harry_x1]

Hi All,
I shoot 300 grain bergers (338 lapua) hand-loaded in lapua brass with my AI AXMC rifle.

I am trying to reduce the amount of functional headspace in the rifle when handloading. I get great accuracy with just neck sizing the brass with no full length body sizing up till 4-5 firings. Post which the brass is too large to chamber properly.

When I use the full length body die (competition body sizing die from Redding), with number 10 competition redding shellholders, my brass chambers (too) effortlessly. Number 10 shell holder should leave the max amount of functional headspace in the rifle. My suspicion is that I might be sizing my brass more than required (even while using the no 10 shellholder).

To solve this, I was thinking of screwing my body size die further up, leaving generous space between shellholder and body die (see pictures). When I size the case this way, what effect it should have on my case? Will the case be only sized for the portion that is inside the die, with no shoulder bump? If after tiral and error, I can find the right amount of gap needed (between shellholder and body die), where case chambers easily, is that the right course of action and will I have found the optimal headspace for my chamber? Or do you recommend that I just let the body size the full case?

I am new to reloading, hence these dumb questions. Any help from experts is deeply appreciated.

thanks
harjeet

 

[nn8734]

“My suspicion is that I might be sizing my brass more than required (even while using the no 10 shellholder).”

Are you not measuring to confirm your cartridge headspace/case head-shoulder datum?

You shouldn’t be guessing whether you’re oversizing or not.

Measure your fired case, run it through the die and remeasure. Ideally you want .001-.002 clearance between case shoulder and inner chamber wall. Esp in a field rifle. Oversizing just excessively works the brass, potentially raises case pressure and in really extreme cases, can result in case head separation (boom).

 

[harry_x1]

“My suspicion is that I might be sizing my brass more than required (even while using the no 10 shellholder).”

Are you not measuring to confirm your cartridge headspace/case head-shoulder datum?

You shouldn’t be guessing whether you’re oversizing or not.

Measure your fired case, run it through the die and remeasure. Ideally you want .001-.002 clearance between case shoulder and inner chamber wall. Esp in a field rifle. Oversizing just excessively works the brass, potentially raises case pressure and in really extreme cases, can result in case head separation (boom).

thanks for your input. I think this is where I am confused. How do I just get that slight .001-.002 clearance between shoulder and inner chamber wall? My Base to shoulder measurement for fire formed brass is 2.334. thanks for your assistance.

 

[nn8734]

If the fired case is measuring 2.334”, set up your sizing die so it bumps the shoulder back .002” yielding a measurement of 2.332”. Or if you want to run bare min headspace, size it so it bumps the shoulder .001” or even .0005” if you can measure down to a half of a thousandth. At .0005-.001” bump you should feel the slightest bit of resistance when closing the bolt while .002”+ there’s typically zero resistance felt on the bolt upon closing.

ETA: I’d use a full length sizing die and standard shell holder. You can (should be able to) accomplish min clearance and size the brass completely with the basic stuff. I used to neck size a long time ago until I realized there wasn’t any real performance benefit over f/l sizing while at the same time I occasionally found some brass wouldn’t chamber as the brass expanded ever so slightly beyond chamber dimensions.

 

[spife7980]

Your fired brass is chamber sized. You need to size it so that the shoulder is .002 less than it measures when fired.

There is no such thing as chambering too easily. Only too difficult. Quit trying to get cute with necksize only and body size without touching shoulders etc. All you’re gonna do is make issues for yourself.