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Old August 5, 2012, 01:12 PM   #1
TacoRC
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Reloading help please 9mm

I have been reloading for some time, and just noticed something really strange.

I am reloading 9mm for my Springfield XD sub compact, and until now never noticed that when I place a loaded round in the clip and place it in the gun (slide back as if the last round from the previous clip had been fired) and I hit the thumb release to load the new round, the round OAL reduces by up to .005.
This happens even with new ammo. After trying to crimp harder, I realized it's not the crimp, but it's the steep angle of the feed ramp causing the problem.

Normally I would set OAL TO 1.125 but the shorter the OAL, The worse the problem. If I increase the OAL to 1.160 then I lose .001-.002. The max being 1.169 leaves to wonder if anyone else has had this happen, and what can be done? I really don't want to get near the max OAL, so this ones got my attention.




Thanks
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Old August 5, 2012, 02:42 PM   #2
Unclenick
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Welcome to the forum.

Shorter, rather than longer COL is what raises 9 mm pressures, so I don't know why you're objecting to the longer COL's. Sounds like they make for better feed angles in that gun. With cast bullets seating out so the cartridges headspace on the bullet rather than the case mouth will give you best accuracy and least leading.
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Old August 5, 2012, 05:33 PM   #3
TacoRC
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I'm not objecting to the longer OAL, but at max I still get the loss of .001-.002.

I'm now not comfortable knowing these changes take place, because these changes are with a properly crimped round. What if a "flake"round is chambered? Would it then lead to a compressed load?

Thanks for the reply...I'm just asking if anyone has heard of this happening in their experience?
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Old August 5, 2012, 05:53 PM   #4
SL1
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Your problem may (or may not) be worse than you realize. The shortening due to feed ramp impact is usually worse for rounds when they are fed by firing another round than when they are fed by hand-racking the slide.

It is best to check for that by firing a round to feed a handloaded cartridge, then carefully ejecting the unfired second cartridge and remeasuring its COL.

Even factory ammo can lose a couple thousandths of an inch when fed by firing a round. So, trying to obtain ZERO is not necessaary. But, repeatedly chambering and ejecting the same cartridge, or having too loose bullets in a handload may give shortening that can seriously raise pressure.

For taper-crimped autoloader cartridges, the real factor in holding the bullet tight enough is not crimp. It is the diameter of the case mouth after it passes over the expander plug, in the step before the bullet is seated. The expanded case should be about 0.002" less than bullet diameter. Cases with walls that are too thin might not get sized down to small enought diameter to begin with, or an oversized expander plug may re-expand them too much. Or, trying to taper crimp too much will actually make the bullet looser by slightly sizing the bullet inside the case, after which the more-springy brass case moves a little off the hardly-springy-at-all lead bullet. And, some Lee Factory Crimp Dies can make some bullets loose in the same manner that the over-crimping does, IF the carbide ring is a little on the small diameter side of the tolerances.

I suggest that you try the fire-fed round test and then tell us how much length you lose. If it is still only 0.002" or less, then I think you are good-to-go. If it is more, then update this thread and we can make more precise suggestions for diagnosing your issue.

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Old August 5, 2012, 05:53 PM   #5
chris in va
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It's called 'bullet setback'. .002 is not much, probably a non-issue if you don't keep chambering it.
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Old August 5, 2012, 08:04 PM   #6
dacaur
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.005 isnt a problem. Not much you can do to stop bullet setback, but as long as you dont keep cambering the same round over and over, you will be fine.

With my carry pistol, any time I remove a round from the chamber for any reason, I unload the mag and put it at the bottom, moving each round up one space. I then shoot the entire mag each time I go shooting, so the most any round is ever chambered is two or three times, which is safe, at least so far.....
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Old August 5, 2012, 08:20 PM   #7
tkglazie
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Quote:
With my carry pistol, any time I remove a round from the chamber for any reason, I unload the mag and put it at the bottom, moving each round up one space. I then shoot the entire mag each time I go shooting, so the most any round is ever chambered is two or three times, which is safe, at least so far....
.

this is an excellent method. The benefits also extend to the magazine spring (yes, it's a magazine, not a clip). If you are like me and keep your "carry ammo" in one mag and use other mags for the range, this method is a good way to ensure the carry mag spring doesnt take a set.
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Old August 7, 2012, 12:10 PM   #8
serf 'rett
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What brand of dies are you using? Loading single stage or progressive?

I haven't noticed setback with my XDm, but I need to double check with some of the new bullets I've been using lately. As stated, over crimping can make things worse.
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