Is it possible…

[Leatherneck]

Is it possible that once fired brass can have a smaller dimension than unfired brass? I shot a box of ammo today, Hornady Precision Hunter 150ELDX in my Remington 7mm-08 and when I got home I checked the shoulders with a SAC comparator and found the fired brass averaged about .002/.003 shorter than the loaded ammunition. The primers look like the are seated properly. The spent cartridge feels like it chambers a little easier as well. I understand that their is spring back in the brass as well. Could I be seeing spring back? I'm relatively new to the whole reloading thing but have read enough to make my head spin. I don't have the reamer print. It has a Kreiger barrel and was chambered by them as well. The rifle shoots sub 1/2 MOA with said ammo.

 

[Roninco]

New brass is at it's smallest dimensions, both in diameter and length. This is often at or below SAAMI minimums and much less than chamber dimensions especially on a factory barrel.
Upon the first firing the brass diameter will first expand to the chamber body diameter. This can cause the case length to initially shorten. If additional pressure is available the case will then lengthen on the base to shoulder axis and subsequently "grow". If still more pressure remains the brass will flow past the shoulder and cause the neck length to increase. This is why case trimming may not be necessary until after several firings since the diameter and base to shoulder growth has already occurred.
So yes, once fired brass can be shorter than new brass. This is why caution is needed if adjusting the sizing die on only the first firing.

 

[Kansaswoodguy]

Idk sounds like an measurement error of some sort.

 

[Bob Wright]

I will add that primers can alter headspace checks if new unfired primers in ammo is not seated below head, and spent primers with raised edges around the primer strike.
See if the new ammo has raised primers and go from there, all fired ones, de-prime and check. Assumption you're checking headspace as well as OAL of fired brass?

 

[Mikecr]

When your case shoulders take their new form, snapping to a higher angle, it pulls necks back and can also lead to your head space tool falling on another datum. The fired cases should be way straighter than the factory ammo. Maybe that's why it seems to chamber easier after fired.

 

[Leatherneck]

When your case shoulders take their new form, snapping to a higher angle, it pulls necks back and can also lead to your head space tool falling on another datum. The fired cases should be way straighter than the factory ammo. Maybe that's why it seems to chamber easier after fired.

That makes sense. I double checked yesterday's measurements this morning using a Hornady comparator. The datum measurements were around half a thousand to 1 thousand less than an unfired case. The Short Action Customs comparator shows around.002 less. The SAC tool does have a 20 degree "shoulder" machined into it.

 

[Bob Wright]

That makes sense. I double checked yesterday's measurements this morning using a Hornady comparator. The datum measurements were around half a thousand to 1 thousand less than an unfired case. The Short Action Customs comparator shows around.002 less. The SAC tool does have a 20 degree "shoulder" machined into it.

Measuring with 2 different headspace tools should give you different results. It's a reference dimension and only applicable to that tool when you zero out your caliper. Just so you know....
Pick one and hide the other forever.

 

[mrrr0809]

Side note…@Leatherneck I'm interested in your Viper scope for sale in the exchange. I don't yet have the privilege of posting in there since my account is so new.

Mods, please forgive me if this against the rules. I'm genuinely sorry. I've been browsing the forums on here for years. I've picked up lots of good info and finally decided to make an account. It's the only way I figured out how to reach out to the seller.

 

[DoneNOut]

Leave it up to a devil to have a case like this!!!

 

[Leatherneck]

Side note…@Leatherneck I'm interested in your Viper scope for sale in the exchange. I don't yet have the privilege of posting in there since my account is so new.

Mods, please forgive me if this against the rules. I'm genuinely sorry. I've been browsing the forums on here for years. I've picked up lots of good info and finally decided to make an account. It's the only way I figured out how to reach out to the seller.

If you want to put your contact info in a message here in this thread I'll get ahold of you that way, or in the thread I have with the scope that'll work to.