338 Lapua base to shoulder maximum

[degreen]

Just measured some fired 338 Lapua brass against some full length resized brass. I got .013 longer on fired brass measuring to the same point on the shoulder. What is the maximum stretch on 338 Lapua brass after firing?

 

[SDPlinker]

Mostly depends on your rifles chamber!

 

[KRP]

With SAAMI spec chamber and cartridge it could be .015.

SAAMI drawing looks to be a copy of the CIP drawing with a couple of dimensions added in inches.

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

If it was mine I would adjust my sizing die.

 

[DUSTY NOGGIN]

New & Revised Cartridge & Chamber Drawings - SAAMI

Cartridge and Chamber Designs Standardized by SAAMI Note: Current Cartridge & Chamber Drawing documents are contained within the SAAMI Standards. They can be found HERE. Newly Accepted Cartridge and Chamber Designs Links to technical data and drawings for the newly SAAMI accepted Cartridge and...

saami.org

 

[QuietTexan]

What die and how are you adjusting it? That's a lot of movement, and begging for a case head separation.

0.010" is a normal gap between a go and no-go gauge to set up headspace for a barrel, but that doesn't translate to that being a reasonable amount of sizing for a case.

 

[KRP]

What die and how are you adjusting it? That's a lot of movement, and begging for a case head separation.

0.010" is a normal gap between a go and no-go gauge to set up headspace for a barrel, but that doesn't translate to that being a reasonable amount of sizing for a case.

.010 is the difference in minimum and maximum headspace not the difference in the go and no go gauge.

 

[degreen]

According to everything I have looked at. The base to body/shoulder junction should be 2.1614". I am using my comparator without an incert, and it sits a little above the junction. Full length sized brass measures 2.191", and fired brass measures 2.204". If my memory serves me right the max difference between a go / no go gauge is .004".

 

[QuietTexan]

I misspoke, I was looking up 223 AI spec gauges and had them on the brain. 0.010" is typical headspace tolerance as mentioned. 0.015", while on the drawing, is too much and means the sizing die is adjusted too far down.

 

[KRP]

According to everything I have looked at. The base to body/shoulder junction should be 2.1614". I am using my comparator without an incert, and it sits a little above the junction. Full length sized brass measures 2.191", and fired brass measures 2.204". If my memory serves me right the max difference between a go / no go gauge is .004".

Forget about the 2.1614 number as you're not measuring this or any other absolute dimension.

With your comparator you're taking a relative measurement between fired and sized brass. It's possible for the chamber and cartridge to be in SAAMI spec and have as much difference as you are seeing. The next time you fire that case it will stretch to fit the chamber again, so it's also possible that doing this repeatedly will give you problems with the cases separating.

I wouldn't want that much difference every time I sized/fired a case so I would adjust the sizing die. If the fired case will chamber easily I would size them without moving the shoulder and fire them again. If you have to move the shoulder that far to get the case to chamber easily I would figure out why and then look into possible solutions.

If you are concerned about the headspace then get a gauge/gauges and check it.

 

[degreen]

Forget about the 2.1614 number as you're not measuring this or any other absolute dimension.

With your comparator you're taking a relative measurement between fired and sized brass. It's possible for the chamber and cartridge to be in SAAMI spec and have as much difference as you are seeing. The next time you fire that case it will stretch to fit the chamber again, so it's also possible that doing this repeatedly will give you problems with the cases separating.

I wouldn't want that much difference every time I sized/fired a case so I would adjust the sizing die. If the fired case will chamber easily I would size them without moving the shoulder and fire them again. If you have to move the shoulder that far to get the case to chamber easily I would figure out why and then look into possible solutions.

If you are concerned about the headspace then get a gauge/gauges and check it.

I am going to have my gunsmith ream the old chamber out. The bolt will not close on the fired brass, and just the pressure of the extractor going over the rim causes the fired brass to stick in the chamber.