Undersize brass - How much is too much??


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williek69
December 11, 2009, 07:40 PM
I am green-horn newbie reloader.

I have a question regarding once fired brass that measures below “trim to” length. I have not found this particular question addressed in any of my reloading related books.

Some .40 S&W brass is .003”-.005” undersize BEFORE trimming.
I also have some .223 Rem that is as much as .010”-.015” undersize. The worst of it is surplus that I know is just 1X fired. It was fired through a semi-auto M4 carbine.

This brass has not been resized or trimmed.

All my manuals address cartridge overall length regarding feed problems, dangers, etc. But none addresses this particular situation. :banghead:

Just how much undersized is OK and how much should be considered grounds for rejection?

Should I be more concerned with semi-auto handgun brass than rifle brass that is to be used in a bolt action rifle? Should I be more concerned with that used in a semi-auto rifle as described?

I just want to be sure that my reloads are ultimately safe to use in the firearms I have.

Thanks up front for your help. :D

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SlamFire1
December 11, 2009, 07:45 PM
Resize the stuff and watch it grow!

Still for rifles, being underlength is not a safety issue. As long as the case neck holds the bullet in place, the ammunition is shootable.

Overlength is bad. If the case neck pinches the bullet in the throat, pressures will climb.

I never check the case length for 45 ACP and 9mm. I load mixed brass, run it through the tumbler and then through the progressive.

It all goes bang.

Sudden Impact
December 11, 2009, 07:55 PM
I've found surplus as short as 1.735".

Mostly Federal, some LC.

I load'em!

Have had no problems so far in semi-auto.

I believe the .223 indexes off the shoulder but am not certain.

Hope this helps but as always, YMMV!

williek69
December 11, 2009, 08:00 PM
Maybe I didn't make myself clear as I could have.

After firing, I deprimed the brass and then tumbled it to clean it up for resizing.

Just because I'm so anal, I decided to measure the cases prior to any resizing whatever. I wanted to see where they were both before and after I resized.

That is when I discovered they were shorter than "trim-to" specs.

Thanks again for your help.

Walkalong
December 11, 2009, 09:52 PM
If you are just curious as to how much it changes when sized, that's fine, but the unsized length is otherwise meaningless.

You are right. I don't remember seeing "how short is OK" covered in manuals either.

I would not even start to be concerned until .223 brass is .020 shorter than the minimum. (After being sized of course) Even at that it would not be dangerous. Only brass that is too long (or drastically short) can be dangerous.

Welcome to THR

williek69
December 11, 2009, 11:15 PM
That's what I was hoping to hear. I didn't see where shorter brass is as important as COAL.

Thanks again for the info.

James2
December 11, 2009, 11:56 PM
You don't have a problem with the 223 being short.

On 40 S&W brass you could get into a problem since the cartridge actually headspaces on the mouth of the brass. 0.005 under shouldn't be a problem, but I wouldn't want to be any shorter.

Roccobro
December 12, 2009, 12:36 AM
Once you re-size the .223, it WILL be longer than it was before.

Justin

williek69
December 12, 2009, 08:36 PM
I resized some of the .223's and they are still .010"-.015" shorter than the trim to length.

They must've been really short from the factory.

Walkalong
December 12, 2009, 09:14 PM
Not unheard of. No worries. You won't have to trim them as soon. :)

Drail
December 12, 2009, 09:27 PM
Most new brass is short.

fguffey
December 13, 2009, 09:23 AM
New brass (loaded-unfired), pull the bullets, measure the length of the case then seat the bullet and fire, measure the length of the fired case and compare it with the case length before it was fired, longer-shorter? Load the case and fire it again, longer-shorter?

There is nothing to be gained by measuring the length of a case after it is fired if the length was not known before firing, measuring again after the second firing will determine the effect the second firing had on the length of the case.

Extreme: From start to finish when forming cases for wildcat chambers the case can/will shorten as much as .040 thousands, not as if it is understood but blowing out does not necessarily mean forward as out or toward the barrel (again: add time), the case fills the chamber, when fire forming wildcats the neck pulls back when the case fills the chamber and if the case was measured before and after every step in the process of forming, the hand loader knows the effect each step has on the length of the case.

Back to Hatcher and his curiosity, he had the shoulder in the chamber moved forward .125 thousands on the 03 then fired 30/06 ammo thinking he knew what would happen, what ever he was thinking would happen 'didn't'. After wards in his observations he made no mention of skid marks caused by the case blowing forward nor did he mention the case getting longer, stretch or flow? What direction?

fguffey
December 13, 2009, 09:37 AM
and the neck shortens when fired, gets longer when sized down and shortens when necked up, another description of the events say the neck gets thicker and/or thinner, the difference in the two stories is determined by finding out which of the two stories was written by someone that measure before and after,

F. Guffey

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