223 brass shortened after firing? Help

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iayote

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I may have a stupid question. I am fairly new to reloading as my dad has taught me to reload in the last few years. I bought some once fired Lake City 223 brass. I first deprimed and f/l sized the brass. Most brass showed 1.765 or longer. My Lyman manual stated to trim to 1.750, which I did. I reloaded 100 of the brass for my new Rock River Coyote carbine and shot them up today. After shooting, i measured over half of the brass and noticed that most of the brass now measure less than 1.750. Most of them are 1.740 - 1.745. Can anyone explain why? Am I doing something wrong? I thought that the brass length would lengthen insteda of shorten? What do I do now? Do I full length size again, and can they be safely reloaded again to shoot? Any help in detail would be very much appreciated.
 
The brass swells out to chamber size when fired and springs back slightly. With the body swelling it can reduce the overall length. When sizing and squeezing the body the brass will grow in length by about .004" or more.
 
Originally Posted By: Orneryolfart357Get a .223 necksizer die. Reload, shoot and keep an eye on brass length. You wont even need to lube cases. Your brass will thank you for it.

Not generally a good idea in this case as it is going in an AR. Slam fires seem to be visited on those that NS for the AR a bit more frequently than those that full length resize. That notwithstanding the chambering will be compromised and extraction of a loaded round will be negatively impacted to a great extent.

Greg
 
Originally Posted By: iayoteI may have a stupid question. I am fairly new to reloading as my dad has taught me to reload in the last few years. I bought some once fired Lake City 223 brass. I first deprimed and f/l sized the brass. Most brass showed 1.765 or longer. My Lyman manual stated to trim to 1.750, which I did. I reloaded 100 of the brass for my new Rock River Coyote carbine and shot them up today. After shooting, i measured over half of the brass and noticed that most of the brass now measure less than 1.750. Most of them are 1.740 - 1.745. Can anyone explain why? Am I doing something wrong? I thought that the brass length would lengthen insteda of shorten? What do I do now? Do I full length size again, and can they be safely reloaded again to shoot? Any help in detail would be very much appreciated.


Brass never shrinks by its self [223 to 223] it only grows. Something in your process of measuring and trimming wasn't right. Probably the way you de-burred the brass left a bit of loose brass on the case mouth when you measured. Re-load and shoot them just fine. When you trim, you must be careful to inside and outside de-burr the cases and make sure no "feathered" edges are on the mouth of the case. That will give you a false measurement.
 
Did trim the brass before or after you ran it through the sizer die? I have seen brass shorten after sizing, specifically lake city once fired 5.56 brass. I would bet if you size then trim and then measure again after firing things would look normal.
 
As a general rule, when you get fired brass from someone/somewhere, FL size it and the sshoot it before you trim it.

Brass NEVER gets shorter from FL sizing, it ALWAYS get longer (or stays ~same if the case was small to start with).
 
I first f/l sized and then trimmed to 1.750.

So, from reading above, now that I have fired these rounds and the length is 1.740 - 1.745. Do I go ahead and f/l size again before reloading? Are they what you all would consider to be too short to safely reload if they are under 1.750 ? Will the brass eventually lengthen? Am I doing something wrong? I hate to ask stupid questions but I was under the assumption that I was taking the right steps.



 
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Full length size and re-measure. If they grow a few thou. No big deal. If they dont, load them up they are not too short. Factory fed brass is that short or shorter. Fl-size after each firing, then measure and if at the max length or longer trim them back down.
 
If you have a reloading manual, read in the front about the reloading process. It will explain a lot. If you dont have one, you need to buy one. You need to resize your brass everytime it is shot. It may be FL resize or just neck sizing but you resize it everytime. No measurements are made until it has been resized. Like stated before, your brass is not going to shrink.
 
Iayote,
I ALWAYS FL resize any new/once fired brass and then measure to see if it needs trimming shorter. I have picked up several thousands of miscellaneous brass (most various military) and some are excessively long right from the start. So I never reload a hull without checking it for length after sizing. Some were so long that I suspect the brass mouth would have jammed in the chamber causing excessive pressure when fired.
Your short brass is only short at the mouth. As long as the shoulder is properly sized by the properly adjusted die the only problem is there will be a little less neck tension on the bullet. Inconsistent neck tension can cause larger groups but the difference is pretty minor and not a safety issue.
 
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Could be your trimmer. If it is a manual trimmer and you put more inward pressure when cranking the handle you could get that much difference. Did you measure each piece of brass after you trimmed it and chamfered them to confirm they all were at 1.750? Rudy
 
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