Case Length n trim

[G38xOC]

If you guys can help me with some of my noob questions , that'd be great !

this is about trimming once fired brass ( wally american eagle & PMC ) to a recommended trim to length . caliber 223

I only have Lyman 49th Edition ( page 137 ) it says trim to length 1.750"
Q : different reloading data uses some what slightly different TTL ?


I have picked up my own brass only that day . been tumbled only .
here are some random measurement .

PMC : 1.746 , 1.743 , 1.737
American Eagle 1.747 , 1.748 , 1.746

it clearly shows that , it does meet lyman's Trim Length .. I've read here saying with care , used brass can be used 6-8 times ?

are these no go ? am i missing something here ?

[G38xOC]

Think I've found my answer ..

The book indicates I'm suppose to Resize/deprime . guess case length will increase after ?

[huckberry668]

yep, they grow about .005" after each resizing. usually once fired brass can go a couple of reloadings before needs to be trimmed.

[joelogic]

Even though the trim length is 1.750", I trim to 1.740" for a consistent crimp because as you can see once fired is all different lengths.

But the don't trim all the time and don't crimp crowd will show up any minute.

[damndave]

Yup, they will grow when you resize them.

[G38xOC]

Thanks
I'm not sure if anyone uses lee brass cutter with case length gauge.
They say to spin it till u don't feel any resistance. Does that mean, that is what factory Trim to spec ?

[bruceflinch]

Yup, they will grow when you resize them.

I thought the neck grew when you shot them?
I thought resizing brought everything but the neck back to original length.

[GeoffLinder]

I thought the neck grew when you shot them?
I thought resizing brought everything but the neck back to original length.

The way it works is the case shoulder is fully forward against chamber neck when firing occurs, case is then stretched back till case head hits bolt face when pressure peaks. When you resize the case, metal that was stretched forward from case base area then migrates forward into case shoulder and neck and causes neck length to grow as a result of this metal moving forward when the die squeezes the case. This forward metal flow is also the reason case head separations are the main result from over-using rifle brass in semi-autos where you full length resize the cases after every firing.

[Fjold]

If you adjust your sizing die so that it resizes the case as little as possible (to fit your chamber) the cases won't grow much at all. I get over 10 reloads with most of my bolt guns without trimming.