If your cases are accurately resized with the shoulder pushed back .001" you'll never see a headspace separation. The only exception is with break open actions like the T/C that can have a serious flex problem adding to the problem of case stretching.
Factory belted magnum ammunition is headspaced on the belt, and they set back the shoulder .012" to .015" for a reason. Their major concern is for their ammo to always fit in any rifle chamber of the same caliber, and they have no concern for more than one shot. However, handloads NEED to be headspaced on the shoulder, and if it's done exactly right, this inherant case wear can be managed very well. If properly reloaded, you should never see a case separation - even with a belted magnum.
The exact size of chambers (and resizing dies) vary quite a lot, so measuring is important - especially when loading already weakened belted magnum cases. The best way to measure your chamber clearance is to compare your handloads to one of your fired cases with a consistently accurate measuring tool. If you plan to get good life from your brass, this is definitely not overthinking a non-existant problem . . . . . it's avoiding that big once in a lifetime surprise.
Our Digital Headspace Gauge shows the clearance that YOUR handloads will have in YOUR particular chamber (at the shoulder). Handloads should have -.002" clearance. If not, you'll see how much (and which direction) to adjust your sizing die.
Our Belted Magnum Collet Resizing Die allows you to drop your belted case in the top and SEE if you need "extra" resizing. If your case fits - it's good to go, and there's no need for more resizing. However, if you have cases that don't fit . . . . then it's obvious that it needs a bit more resizing.
The reson it works better than a conventional die, is that it pushes "inward" to resize the case instead of plowing the brass back towards the case head where it accumulates at the belt and actually increase case diameter. Read my website, and you'll see why these tools are becoming so popular. Thanks for the chance to explain.
You can contact me anytime by phone or email. I'm almost always available to help a fellow shooter (whether they're a customer or not). Our mission statement is to help shooters make the best handloads possible, and to motivate as many as possible to preserve our gun rights.
I have a couple of questions for you.
Having loaded numerous belted mags for many years, I have never experienced this 'bulge' above the belt that you describe, how is it formed on a section of case that is part of the solid web?
If you're referring to the expansion line of the web/wall juncture, this is actually pushed forward during resizing, which is part of the reason that oversizing causes case seperations, the brass is thinned in this area from overstretching, but the brass still flows forward into the neck.
The physics of this brass flow doesn't support your theory of this 'bulging' ahead of the belt.
Can you please explain how this occurs.
The bulge on belted magnums happens just "above" the case web. If a case is going to stretch - this is where it will happen. That's why you only see case separations in this part of the case.
So, why does this bulge happen only on belted cases? It's because factory loads headspace on the belt (and headspace at the shoulder is off by a mile). The very first firing REALLY stretches (and seriously weakens) the case. That's why belted cases need extra attention when reloading. If you measure the area above the belt (and just above the web) you'll see a large bulge that gets larger at each reloading. New cases start out at .507" above the belt. You need to measure your cases!
It's obvious that the brass flows forward during firing. In fact, the brass flow you're referring to comes FROM just above the web. Read my website, and you'll get a better understanding of what happens when firing (and reloading)a belted magnum case. My website fully describes the whole story. If you have more questions, just let me know.
Last edited by larrywillis; 08-09-2009 at 12:28 PM.
There's no way to reduce the thinning of the case above the web. However, our collet die manages the problem by pushing the brass inward, not swaging it back against the belt.
The top of our die is a case width gauge that shows when this "extra" resizing is needed. Our collet is then used to resize the case to minumum SAAMI spec (not the original case diameter). More thinning is accomplished by controlling headspace at the shoulder.
Our Digital Headspace Gauge is designed to show reloaders exactly how far to push the shoulder back - without guessing.