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40SW case variation


Hubcap52

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I did a random weight check on my 40SW brass (assorted headstamps). It was cleaned and unprimed--just the brass. I checked the case length and they were all the same, but as much as 10.5 grains weight difference:o!!! Is that too much? I don't usually sort handgun brass, but should I?:blink:

Edited by Hubcap52
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I'm not as concerned about the lack of weight uniformity. I doubt there are many, if any, people who could tell the difference in accuracy with a hand-held firearm at normal pistol distances with the kinds of deviations I'm talking about here. I'm not talking about bench-rest accuracy.


My concern is not the presence of the weight/capacity deviation, but the amount of deviation-- well over 10%. I don't know how much a % of change in case capacity affects pressures, only that it most certainly does. All reputable manuals advise reloaders of semi- or full-auto firearms to make sure the ammunition does not allow for bullet setback for this very reason.

 

My concern is about the safety of the ammo, because the weight is a factor in determining case capacity, and therefore pressure, and therefore safety.


If you change your powder charge by that amount, you can very quickly go from safe to unsafe (or vice versa) pressures. It's also my understanding that, because of the nature of smokeless propellants, the pressure curve can rise exponentially rather than linearly at unsuitable pressure levels (high or low).

Edited by Hubcap52
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I sort and use one manufacture, only for consistency. As you stated, there are large differences, and a specific load can vary greatly in fps between them. Because I load to meet a power factor, I try to get as close to it with out falling below it. Using different cases can make this a gamble, and at the cost of going to a level 3 match, and getting bumped into another class, I think it is worth it.

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19 hours ago, TDA said:

This is why you use a chronograph and work your way up when developing a load for your particular firearm.

I have two chronographs and do work up safe loads.

 

18 hours ago, noylj said:

Since it hasn't been a problem for over 100 years, it isn't a problem now.

Watch for cases with "shelves" inside, as they actually might cause a problem.

 

Sounds like the optimist that fell off the Empire State Building...going by the second floor window they heard him say, "So far, so good."

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I normally shoot mixed headstamp .40 and chrono check occasionally to make sure I am USPSA legal.  I have not seen enough of a difference to be concerned over the last 4 years for general shooting.  That being said, for the last two years, when I go to major matches I buy matched headstamp brass, so I don't have to worry about slight variations in internal volumes.  

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I don't have any issues with mixed head stamp 40 brass.  Having said that, I run same head stamp for major matches.  

 

I can feel a differnce in 9mm, especially 9 major.  

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>Sounds like the optimist that fell off the Empire State Building...going by the second floor window they heard him say, "So far, so good."

 

No, it sounds like someone who is looking at over 100 years of experience and NOT simply sitting back and imagining things to worry about.

If you like, feel free to sort by length, head stamp, and weight, just don't forget to measure and weigh your bullets for sorting also. 

It can't hurt, but does it gain you anything? Test and let's see the results so we can all learn.

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Since I see that 57K mentioned GFL headstamps, I would like to ask a question about these in particular.

I have noticed that when ever I get a case that takes noticeably more force to size the case, it is always a GFL headstamp. I was curious if this was due to over size case, heavy wall or excessive case expansion during firing. These are usually range brass pickup's (40 caliber) so I don't know if they are factory once fired or someone's reloads. I guess I could just take a minute and measure the case wall and OD next time I run across some.

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