How much shoulder bump is unsafe
- Thread starter TacosGigante
- Start date
Light (powder puff) load to fireform the brass, going to have to burn up some components
Can you push a shoulder forward with a resizing die? Is seems like there is nothing to push the shoulder forward.
A little bit, i.e just before it starts to bump it usually squeezes the body and pushes the shoulde forward. 001 or so. A lot of 300wm brass grows .02 on its first firing. That big stretch eats up some case life. There are few ways to fire form the brass while mitigating some or most of the stretching at the base. One woukd be a lower charge and jamming the bullets into the lands. Another method would be to create a false shoulder. For this you will need to expand the neck with a larger expander .338 or .358 something like that. Then you slowly size neck lower and lower until the larger diameter of your neck gives a tight fit in your chamber.
I am a famous cheap ass, but if it was some LC or other cheap common brass. I would toss it. Lapua 300wsm brass. I would put some work into to save.
I would shoot some light charges with jammed bullets and see how the cases react becuase its the easiest method.
Does just shooting light charges mitigate base stretching? To my knowledge it does not.
The reason to shoot a light charge with a jammed bullet is the pressure spike you get from jamming bullets. You go in a with a ragged edge load and jam bullets you're gonna pop primers.
The reason to shoot a light charge with a jammed bullet is the pressure spike you get from jamming bullets. You go in a with a ragged edge load and jam bullets you're gonna pop primers.
I usually bump 3-4 thou. This ensures chambering when the gun is dirty and/or wet.
Have yet to have a round that would not chamber or ignite in the last 16-18K rounds of match ammo loaded and shot. Actually its more impressive I haven't got a dud primer in that time.
After the 3rd firing the cases really stop growing any more than maybe a thou, and trimming is just cleaning up the edges.
Annealing will also help. It will make your sizing much more consistent and you wont have to worry about cracked necks or case mouths.
Well prepared brass that is not trashed by too much pressure will last until the primer pockets become to loose. This could be like 5x on cheap brass to 40-50x on really good brass like lapua/alpha/peterson. If you oversize them you will get case head separation eventually as you are thinning out that case web every time you size. If you shoot matches chances are you will loose the brass to rocks and tires way before its shot out.
Have yet to have a round that would not chamber or ignite in the last 16-18K rounds of match ammo loaded and shot. Actually its more impressive I haven't got a dud primer in that time.
After the 3rd firing the cases really stop growing any more than maybe a thou, and trimming is just cleaning up the edges.
Annealing will also help. It will make your sizing much more consistent and you wont have to worry about cracked necks or case mouths.
Well prepared brass that is not trashed by too much pressure will last until the primer pockets become to loose. This could be like 5x on cheap brass to 40-50x on really good brass like lapua/alpha/peterson. If you oversize them you will get case head separation eventually as you are thinning out that case web every time you size. If you shoot matches chances are you will loose the brass to rocks and tires way before its shot out.
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I've been getting randomly oversized brass, shoulders that were bumped 8-15 thousandth. I found 9 pieces in a lot of 340 that were in this windows. Last week I decided to load them and see what happens. Shots 1 and 2 were fine. Number 3 was not. Case separated as I extracted. This was with 6x fired 6gt.
300WM belted brass typically stretches .015-.020 first firing. (So switched to Peterson Long brass)
My No4MK2 Enfield stretches some brands of brass .050. Lol
Most my battle rifles stretch the 308 cases .010-.012 (M1A, FAL, etc)
Heck, lots of virgin brass gets stretched .010 in most factory chambered rifles.
So to answer your question, I highly doubt, with great certainty, there will be anything "dangerous" about shooting them .020 under. You might see them creeping to case head sooner though. I wouldn't just toss them thinking you ruint them.
My No4MK2 Enfield stretches some brands of brass .050. Lol
Most my battle rifles stretch the 308 cases .010-.012 (M1A, FAL, etc)
Heck, lots of virgin brass gets stretched .010 in most factory chambered rifles.
So to answer your question, I highly doubt, with great certainty, there will be anything "dangerous" about shooting them .020 under. You might see them creeping to case head sooner though. I wouldn't just toss them thinking you ruint them.
What conditions are you looking for that tell you a case is going to rupture. The case I had that ruptured didn't appear any different than the rest of my brass other than being bumped extra. At least that I could see or know to look for.
I did have several that had the tell tale scoring on the case body. That's what prompted me to start measuring every piece I had resized and start tracking down why I had excessive bump.
Oh boy, like before they start looking like the one on the left. Though I've also had them appear like the one in the middle too without warning, but only a few times in the past 30yrs.
Sure. I pitched all 3 of these. What I'm saying is if they dont have these lines, what would you be looking for? The case rupture I had last week didn't have these lines and I couldn't see anything wrong with it. I knew it was bumped excessively because I had measured.
Borescope the insides of them to see any premature stretching. Or the old bent paperclip method to detect the separation from the inside before it goes to the outside. I also had a Lapua case rupture once. The rupture was so clean it looked like a laser cut the case head off. Nobody could explain it, not even Lapua themselves.
If you really want to keep the brass around I'd do a false shoulder to re fireform them. Wouldn't be afraid to jam and fireform them either but I'd think you'd get more case stretch that way.
I'd think many shellholder/die combos wouldn't let you bump the shoulder a full 0.020" on a wsm?
I'd think many shellholder/die combos wouldn't let you bump the shoulder a full 0.020" on a wsm?
Jam the bullets and shoot 'em. .
020" is probably not enough to have a case head separate completely but will probably start to crack if you don't jam the bullets
020" is probably not enough to have a case head separate completely but will probably start to crack if you don't jam the bullets
