Trimming .223 for a 5.56 rifle

[GLOOB]

New to reloading rifle.

I've measured my once-fired, sized .223 cases. Of the first couple dozen, they're all below 1.76". They range from 1.744-1.758".

Seeing as 5.56 trim length is longer, will I ever need to trim these cases for a 5.56 chambered rifle? I don't plan to crimp.

I'm not trying to cheap out. I already bought a nice trimmer. I just don't want to waste any effort unless there's a good reason. I don't own any .223 chambered rifles. If I don't trim and don't crimp, will I see any difference in accuracy out of a 3-4MOA 5.56mm rifle?

I've heard cases stretch the most on the first firing. Is this correct? Will they likely ever get past 5.56 max length before they split?

Maybe I should have made this into a poll.
1. Don't trim unless they get past 1.772?
2. Trim to 1.760" if/when necessary.
3. Trim them all to 1.75", since many are shorter than that, to make them more uniform.

 

[243winxb]

If the case is longer then 1.760" after sizing, you should trim off .010" This is the basic rule. SAAMI lists a minimum trimmed length of 1.730" RCBS X Die instruction say to trim off .020" below maximum of 1.760"

 

[GLOOB]

Trim off 0.01/0.02"? Or trim to exactly 1.75"/1.74"?

And if this was 5.56 stamped brass, would I be trimming at 1.772" and trimming to 1.762/1.752"?

Finally, does something bad happen if you try to run full length 5.56 brass through a 223 Lee die set?

 

[243winxb]

Trim to lenght is 1.750" This is the standard when brass has grown over 1.760" The 223 & 5.56 have the same trim length. There chamber are different. But both are loaded the same.

 

[243winxb]

Don't trim unless they get past 1.772?

The 1.772" is a chamber measurement on the SAAMI drawing. http://www.saami.org/PubResources/CC_Drawings/Rifle/223%20Remington.pdf Some chambers are cut longer or shorter, i would guess. You need to measure your chamber if you want to go longer then the standard maximum of 1.760" If you brass is not trimmed and gets to long, the bullet may be crimped into the case by the chamber on loading. This will result in very high pressure, blowing up your rifle.

 

[Walkalong]

Trim it all to 1.750. Do not load any brass that is at or over 1.760. Trim it. It doesn't matter if it is a .223 or a 5.56 Nato chamber. Trim it to 1.750.

Will they likely ever get past 5.56 max length before they split?

They most certainly can.

1. Don't trim unless they get past 1.772?

Wrong

2. Trim to 1.760" if/when necessary.

Wrong

3. Trim them all to 1.75", since many are shorter than that, to make them more uniform.

I like to trim, deburr, and chamfer them each time. I would rather just do that than measure them all.

 

[Cemetery21]

In my experience, they will need trimming several times before they split. I normally get somewhere over 10 loadings from .223 and trim about every
2nd or 3rd firing (whenever they get over 1.760").

 

[GLOOB]

Great info. I'll trim them all to 1.750. Thanks to all.