trimming brass when 0.010" too long?

[swift]

Before I trim hundreds of cases by 0.010", I wanted to check that I'm not doing something else wrong. I did a case resize of a .223 case and it fits nicely into a .223 case gauge from Dillon, except that a tiny amount sticks out.

When I put a bullet in (without any primer or powder) and then load it into the rilfe from the magazine, the round sticks in the chamber and I need to it the charging handle pretty hard to eject the round.

When I remove the 0.010" of metal from another sized case and load a bullet, it fits perfectly into the rifle and it's effortless to remove it by pulling the charging handle.

The case length is supposed to be trimmed to 1.760" and my cases are 1.770".

Does this seem reasonable that the 0.010" would make that much difference? I just wonder if there isn't antoher error elsewhere.

[Pryde]

First question would be: what kind of barrel is it?
Some AR15 barrels have looser NATO chambers with long throats and some have tight .223 chambers.

[FLIGHT762]

1.770" is .010" too long! The MAXIMUM case length is: 1.760".
When you trim, you trim .010" BELOW the maximum length. Your trim length should be 1.750". This will give you a few firings before you have to trim again. If your cases are 1.770", you should trim .020" from them.

When I trim my larger cartridges, I trim .015" below maximum. You don't want to trim much more than that.

[Jonathan Doe]

Usually, SAAMI spec is little longer than the loading manuals. So, trim it .010" longer may be okay. Try the sized brass in your rifle to see if it fits.

If the loaded ammo sticks, maybe you are dealing with the bullet seating depth, or the cases not sized properly, not the case length.

[FLIGHT762]

First question would be: what kind of barrel is it?
Some AR15 barrels have looser NATO chambers with long throats and some have tight .223 chambers.

The chambering doesn't matter in relation to case length. Case length specs for the 5.56 NATO is 44.70MM. This equals 1.759839" or rounded off to 1.760", which is the same for the .223 Remington.

Chambers are cut different and the cartridges are loaded to different pressures, but outside loaded cartridge dimensions are the same.

[God Bless The Mauser]

I'm using a Lee case trimmer and it trims them to 1.740"

[buffybuster]

Shooting cartridges with excessive caselength can lead to dangerous chamber pressures. Those cases should be trimmed to .010" below the maximum allowable caselength.

If your cartridges are getting stuck in the chamber or are difficult to extract, the casemouth may be entering the throat area. This is potentially dangerous since during firing the casemouth needs to have the room to expand, releasing the bullet. If the casemouth becomes pinched in the throat area, it cannot release the bullet. The bullet is finally released when excessive pressure has built up and forces the bullet from the casemouth.

Most OEM chambers are cut toward the larger end of the specification to minimize this possibility but if yours is not large then this situation could occur.

[FLIGHT762]

Usually, SAAMI spec is little longer than the loading manuals. So, trim it .010" longer may be okay. Try the sized brass in your rifle to see if it fits.

If the loaded ammo sticks, maybe you are dealing with the bullet seating depth, or the cases not sized properly, not the case length.

The cartridge drawings in the loading manuals are SAAMI spec drawings. I've never seen a .223 Remington case length specification over 1.760" in any of the manuals.

In the original post by swift, he specifically said that the 1.770" cases stuck. When he trimmed them to 1.760", they chambered and extracted properly. If there was a bullet seating(C.O.L.) problem or an undersizing problem, the 1.760" length rounds should have caused problems.

Swift, trim your cases to 1.750" and you are good to go.

[swift]

thanks

I am using a DMPS .223 SS barrel.

Thanks, I'll trim them to 1.750"

[bohoki]

I'm using a Lee case trimmer and it trims them to 1.740"

my lee trims to 1.745 but i think the spud will make them smaller and smaller as the little tip wears


i measure all and any over 1.755 get trimmed

there is a magical length that will blow up your gun
what happens is that its just long enough to go into battery but has the little lock nubs slighty not all the way locked

so keep them short

[God Bless The Mauser]

Any way of using fire formed brass even if it's trimmed to length?

[joelogic]

Yea just neck size.