I bought new 308 Lupua brass. Measured when new and all brass was 2.005 to 2.007. After 3 firings I measured the brass to see if it needed trimming. All the brass was shorter, from 2.001 2.003. What is going on? Any help would be greatly appreciated.
- Thread starter jbryant
- Start date
I measure my cases after I full lenght resize them to see if they need any trimming. I used LC M118LR once fired brass, in my experience after I clean them and resize them, they need to be trimm. I do not know anything about the Lapua brass except that they are good brass but never used them, I figure that the process is the same.
Are you full lenght or neck sizing?
Are you full lenght or neck sizing?
I have done both ways. I appreciated your response. I really thought someone would have answered this question with a logical reason. This is my first post and I am afraid that it is a stupid question and the experts will not waste their time responding. I will hang in their an hopefully fiqure it out. I also would like to know what the minimun lenght of a 308 case before you DX it. Any Response will be appreciated.
I have had the same thing happen with Lapua 6.5 Grendel brass. No clue what causes it. Info would be appreciated.
Are you full length re-sizing every firing? I recently purchased a couple cases of Lapua .308 brass and have used about half of it so far. As you mentioned, cases were between 2.005" and 2.007" out of the box. After 1X-firing/cleaning/annealing/full length resize, the cases averaged 2.010" to 2.014". I'm certain much of that comes from the resizing process. If you're only neck sizing, maybe not so much case length growth, if at all. I can easily envision how brass could be moved away from the neck region of you're not full length resizing. On top of that, if you're using SS pins for cleaning, a certain amount of brass will be "removed" due to peening from the SS pins during tumbling. Although I would not think that should ever amount to a few thousandths, it could be the combination of peening and brass flowing away from the neck region. Along the same line, I only tumble cases with SS pins for 45 min - 1 hr in order to minimize peening. Even at that length of tumbling, there is visible peening of the case mouths. Not sure how the case mouths would look if they were tumbled with SS media for 2-4 hrs, as I've seen some people describe. If you figure it out, let us know what the cause was. Good luck.
I see the same thing with virgin lapua brass on first firing. Figured it was just the fire forming as the case expanded in girth and shoulder to the chamber it actually shrunk in OAL. When I FL size after 2-3x firing they grew in COAL and need trimming. I'm only FL sizing every 2-3 firings using a forster bump/neck die all other times.
Don't worry, it will grow after it is sized. Shoot it again and measure it after it is sized. Sizing pushes it back to a smaller diameter and the brass has to go somewhere. Length.
at the moment of the pressure building inside the cartridge,the brass flows where the same brass can find some free space to go_ if your chamber dimension (diameter) allows that, that is what happens: brass seems gettin'shorter because it has grown larger_ don't worry, it's normal_
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You know I never thought of that but I do both. Neck size & stainless steels pins. I will fl size and tumble the old way with some new fire formed brass and see if it makes a difference. I really appreciate you taking the time to respond. As you can tell I do not get to check my computer that often. I will let you know the results.Thanks again.
I finally had a chance to read the other responses and this could be normal and will grow. Makes perfect sense. I really appreciate everyone taking thier time to help. This was my first post ever on a forum and very pleasd with help from fellow shooters
This is more noticeable if you have a run of the mill chamber i.e. it could be "oversize" because of rough manufacturing.
...true_ ( 7,62nato semiauto mil.chambers have teached me this )
