7.62X54 Brass Dimension ?

[hylander]

So my Hornady book shows trim lenght at 2.104
But my new PPU brass measures 2.097
Then I read that new Lupa brass measures 2.086
Original Milspec is 2.115
That is .029 difference between Milspec and Lupa and .018 between Milspec and PPU
Has me wondering what is going on ? Especially with Lupa seeing how they are suppose to be the end all
when it comes to quality brass

[texassako]

Well, one thing you have to remember is the Lapua is 7.62x53r. It even says so on the headstamp. It is .5 mm shorter than x54r, or .02", and there are Finn rifles that will not chamber anything but x53r.

[daengmei]

If you're thinking the milspec number is meant to mean "exactly this length" then no it's not. That number is the max length that military ammo cases should meet so that the cases fit all chambers for 7.62x54r. Hornady trim to length allows cases to "grow" some before they are too long to fit chambers, you should get several firings before trimming is again needed. PPU and Lupua length allows even more "grow" time. The cases grow in length or stretch with every normal/high pressure firing, and eventually need trimming to a shorter length. That length might be somewhat different depending on which reloading manual you use, but they will/should all be shorter than the Milspec length. You will find more or similiar information if you review the reloading manual for material concerning Case Length Measurement and Case Trimming. I hope this helps.

[hylander]

Thanks guys, I understand the brass stretching and Min/Max.
I was wondering why they have not settled on a standard like most cartridges.
My current batch of PPU brass with 4 firings measures 2.097, same as it did new, it has not stretch at all :smile: