Dent in brass with light cast loads.

[Kegcaissy]

Hi!

While shooting my finnish mosin with unique and 155gr cast, as usual, i've found these dents in my brass. All the cases were fired in the same gun but some of these have this big dent in it. What is happenning?

Here's my recipe:

Lee 312-155gr, WW, Aluminium GC, 10gr Unique.


Here's the brass cases:






Thank you

 

[propliner]

It looks to me like some gas is escaping rearward around the neck and past the shoulder and getting trapped in that area before the rest of the case expands to seal the chamber. Try cleaning the chamber thoroughly. The chamber in the neck area might be out of round or have some crud caught in it.

Higher pressure loads might prevent it, or sizing your brass larger with a different die might help as well. Also try neck-sizing if the brass is to be fired in that gun only.

 

[just having some fun]

gas is passing by the shoulder (ie not enough pressure to seal)
neck size the brass
and up the powder charge ---- as little as 1/2 g might do it

 

[c-fbmi]

Yep, I have experienced this before, either increase your load to up the pressure or only size 1/2 the neck using cases fired in this rifle with full pressure loads. 1/2 neck sizing will hold your cast bullet fine and using full power fired cases allows your lower 1/2 neck and shoulder to seal.
Those cases will be fine, just 1/2 neck size them and then load to a full power load and they will fire form back out just like new, no need to scrap them.