.223 brass got shorter - what happened?

[IMtheNRA]

I reloaded about 250 rounds of .223 last night, using my 2x-fired brass, mostly nickel plated R-P, and some mixed headstamp unplated brass. All the brass was trimmed on a Giraud trimmer to about 1.751-1.753 range.

After shooting it all today in a Colt AR, I cleaned and resized the brass, planning to reload it again. After resizing it, I was surprised to see that most of the brass now measures 1.748-1.750

One of the cases was only 1.739 !

I don't know if my brass got shorter during shooting or resizing as I did not measure the brass prior to resizing it.

While I used an RCBS X-die to resize this brass today, I did so with the X-die mandrel raised well above the case mouth - about 8 or 9 turns, so I don't see how the X-die could have acted any different from any other sizing die, as I wasn't using it's unique "X-die feature" which keeps the brass from growing longer.

***Edited to correct the typo in case length - when posted, I left the digit "7" out of the measurement!

Any idea why this brass got shorter and should I be worried?

 

[beatledog7]

Why are you trimming so short to begin with?

Standard trim-to for.223 is 1.750.

 

[littleguns223]

I agree why are you trimming so short? Max 1.760 trim to 1.750.I trim all my 223 brass after resizing. I can shoot it 2 or 3 times before I to have to trim it. If you shoot a hotter load you might have to trim sooner.

 

[cfullgraf]

I don't know if my brass got shorter during shooting or resizing as I did not measure the brass prior to resizing it.

Generally, a case will get shorter upon firing. The case expands to fill the chamber on shooting and does not return to the original size. The brass has to come from somewhere so it shortens up the overall length.

When you resize the case, it will get longer again. Upon firing, the case walls also get a little thinner because they have stretched when the case filled the chamber. Resizing brings the outside diameter of the case back to standard but it does not change the case wall thickness. Again, the brass has to go somewhere so it pushed out the mouth of the case and the case gets longer.

It is best to always trim cases after resizing.

Hope this makes sense.

As others have said, you numbers for case length are a bit off. Hopefully it is only instrument error, operator error, or fumble fingers.

 

[IMtheNRA]

Thanks for catching my typo! That's what I get for trying to figure this out in the middle of the night

I just corrected my original post with the actual brass length measurements.

 

[243winxb]

Any idea why this brass got shorter and should I be worried?

Colts have big fat , long chambers. Don't worry. Brass can get shorter on firing. SAAMI minimum is 1.730" Below 1.730" may not be usable. Less/to little neck tension for an AR if to short.

 

[helotaxi]

Depending on which specs you look at (there are at least two SAAMI specs with different dates floating around for the .223Rem) the min length is either 1.730 or 1.720. In any case, I'd be happy that I didn't have to trim it this time around and press.

 

[beatledog7]

Well now my original question makes me look silly! Really, the numbers were different before.

Merry Christmas, and Happy Holidays everyone!

 

[IMtheNRA]

Beatledog7 - I'm the one who looks silly. Thanks for catching my typo! Merry Christmas and Happy Holidays to you as well!!!

 

[Clark]

1.771"
I loaded, fired in Ruger #1 V, and resized [should be .001" shoulder push back per Ruger #1] 13 times with .246" bushing in S die and loading with 25 gr Surplus bulk IMR4895 and 60 gr TAP moly bullet 2.26" [H322 like] ~ 66kpsi
fire
1.768"
resize
1.775"
fire
1.772"
resize
1.778"
fire
1.775"
resize
1.780"
fire
1.776"
resize
1.782"
fire
1.776"
resize
1.783"
fire
1.778"
resize
1.785"
fire
1.778"
resize
1.788"
fire
1.778"
resize
1.784"
fire
1.779"
resize
1.785"
fire
1.780"
resize
1.785"
fire
1.780"
resize
1.786"
fire some resistance closing on loaded cartridge, no resistance closing on resized case
1.781"
resize some resistance closing on loaded cartridge, no resistance closing on resized case
1.787"
fire some resistance closing on loaded cartridge, no resistance closing on resized case
1.782"
resize some resistance closing on loaded cartridge, no resistance closing on resized case
1.788"

What does it all mean?
It gets more longer from resizing that it gets shorter from firing.

 

[IMtheNRA]

Hello again everyone, I realize that brass gets shorter after firing, but I'm used to it getting longer after resizing, at which point I trim it.

I've never had brass that got fired, resized, and then ended up even shorter than it was before I fired it.

Could it be that the RCBS sizing die does not stretch the brass like the Hornady dies that I've been using until now?

 

[Blue68f100]

The RCBS X-Die is suppose to limit the stretching during sizing. On initial sizing your asked to trim your die -0.020 below MAX. When you adj the pilot mandril down it limits stretching during resizing.