NAS3 5.56 Cases - Tikka 223 w/ 88 TMK

[Schmo]

Pretty lame that they are that short.

So yours are 6 thou short compared to new brass. They are intentionally 3-5 thou short to allow case stretch. So you’re barely over that by 1 thou. Carry on

 

[pods8 (Rugged Stitching)]

They are intentionally 3-5 thou short to allow case stretch.

These brass that are once fired and thrown away intentionally allow for case stretch vs being supported? Is that something in the design or sammi spec? I am not in the know, it just seemed counter intuitive as a statement.

 

[wind gypsy]

So yours are 6 thou short compared to new brass. They are intentionally 3-5 thou short to allow case stretch. So you’re barely over that by 1 thou. Carry on

Why would they need almost the entire SAAMI tolerance for length to shoulder (0.007") less than brass cases which probably stretch MORE?

I'd be surprised if these cases are not below SAAMI min case size spec. They are 10 thou short of my chamber which must be close to SAAMI min headspace.

Edit: looking at SAAMI spec to shoulder, min cartridge to max chamber is a 0.014" difference.. Seems that it might be at or slightly higher than that max difference in Ben's gun.

 

[wind gypsy]

These brass that are once fired and thrown away intentionally allow for case stretch vs being supported? Is that something in the design or sammi spec? I am not in the know, it just seemed counter intuitive as a statement.

Agree that it seems counter intuitive. They seem to be less malleable than brass and cant be reloaded, so why would they have a sloppier fit?

I did send Shell Shock a message inquiring about this.

 

[wind gypsy]

Guys on the Hide reported that the undersized cases seem typical.. I'll try em with 450s or #41 primers to get a little thicker cups. Seems my headspace is likely a hair shorter than Ben's.

 

[Thegman]

So yours are 6 thou short compared to new brass. They are intentionally 3-5 thou short to allow case stretch. So you’re barely over that by 1 thou. Carry on

From what I've seen, NAS3 (Nickel Alloy Shell) cases, don't, and aren't designed to stretch appreciably compared to a brass case. The short base-to-shoulder length is likely creating a larger issue than it would with a brass case which can stretch much more easily.