Thread: Fireform markings

I've just finished fireforming 100 Norma 300wsm cases into 7wsm (against best advice) and about half the cases have a very bright ring at the top of the web. Some also have a bright ring where the old body, shoulder junction was.

The 300wsm cases were sized so that the false shoulder in the neck set zero headspace and the projectiles were lightly jammed into the lands.

I've had case head separation before but that ring was much duller and wider than these rings.

I don't think it's a die mark because none of my Federal 7mm wsm cases have the marking.

To make matters more confusing I sectioned one of the worst offenders and there's absolutely no sign of thinning at the ring (of this case).

Anyone experienced anything like this? I'm gonna have to keep a very close eye on them.

Photo, the colour change above and below the line is also there, not just the camera

What case measure each side off the mark? Diameter wise

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No real experience here but any cases i have fired in a large chamber end up lookin like that.
The 303 is a shocker for it.

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All measurements between 0.553"-0.554" above and below. No noticable difference. I've been told not to worry about it on that other forum.

Its either where your die bottomed out or where the strength of the web overcame the pressure of the shot and allowed the case to expand to "chamber size" above that point

Your sectioned case looks fine, perhaps run a pin along the inside to see if you can feel a divot indicating thinning just for peace of mind.

Good to go

Originally Posted by Cyclist

Its either where your die bottomed out or where the strength of the web overcame the pressure of the shot and allowed the case to expand to "chamber size" above that point

Your sectioned case looks fine, perhaps run a pin along the inside to see if you can feel a divot indicating thinning just for peace of mind.

Good to go

+1 GTG

The sectioned case looks sweet
Good to go in my eyes

Fire forming ESP AI is an art and some people have no idea and create issues for themselves and others

Yours look mint

I run fairly hot loads in my 300 wsm(also using norma brass) and my cases almost always look like this. Thought it might be a problem myself but im on load number 5 on some cases and they are still sweet

Originally Posted by Spanners

The sectioned case looks sweet
Good to go in my eyes

Fire forming ESP AI is an art and some people have no idea and create issues for themselves and others

Yours look mint

+1 FF AI or any cases should be so easy. Can be a hassle
It is once you have it sorted.

Have you tried forming without projectiles Jpayne?



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My money is on the dies making that mark
Colour a case in top to bottom with a vivid (Tactical cases now) and you'll soon see

Your sectioned case looks fine to me. I have exactly the same marks on .257 and .280 cases when fire-forming to AI and have sectioned cases like you. Having confirmed they are OK, I've gone on to use them without any problems. Just my experience. Good idea to do as you have done and err on the side of caution. and the usual disclaimers when discussing any reloading activity apply.

The marks on my improved cases at the original shoulder line following fire-forming often look to be a problem - quite bright and crystalline looking, with an appearance like the brass will let go on the next firing - but I have trusted to the adequate annealing of the parent cases and AI-forming isn't asking that much of brass, sectioned a couple to confirm adequate thickness, and sure enough the brass has subsequently been fine. Failure has never occurred at that point.

I also get the distinct line above the web on both the 257AI and the 280AI from both the chamber on expansion and sizing dies on re-forming at the lowest point on the wall where contact occurs as mentioned in earlier posts. Quite useful as the position of this seems to be a good indicator as to how sloppy the chamber is cut, and then to some extent can then also be used as an indicator of peak pressure on firing, and also then how much the brass is being re-worked on body sizing. Thinning at this point on my cases produces a definite hollow on the inside of the wall opposite this ring. Case failures when they have occurred have been at this point (or neck splits) but only from repeated firing -forming cycles, the progression of the thinning can be tracked by feeling inside the cases. The mark alone is not in itself an issue IMO.

Your sectioned case looks fine to me. I have exactly the same marks on .257 and .280 cases when fire-forming to AI and have sectioned cases like you. Having confirmed they are OK, I've gone on to use them without any problems. Just my experience. Good idea to do as you have done and err on the side of caution. and the usual disclaimers when discussing any reloading activity apply.

The marks on my improved cases at the original shoulder line following fire-forming often look to be a problem - quite bright and crystalline looking, with an appearance like the brass will let go on the next firing - but I have trusted to the adequate annealing of the parent cases and AI-forming isn't asking that much of brass, sectioned a couple to confirm adequate thickness, and sure enough the brass has subsequently been fine. Failure has never occurred at that point.

I also get the distinct line above the web on both the 257AI and the 280AI from both the chamber on expansion and sizing dies on re-forming at the lowest point on the wall where contact occurs as in earlier posts. Quite useful as the position of this seems to be a good indicator as to how sloppy the chamber is cut, and then to some extent can then also be used as an indicator of peak pressure on firing, and also then how much the brass is being re-worked on body sizing. Thinning at this point on my cases produces a definite hollow on the inside of the wall opposite this ring. Case failures when they have occurred have been at this point (or neck splits) but only from repeated firing -forming cycles, the progression of the thinning can be tracked by feeling inside the cases. The mark alone is not in itself an issue IMO.

Originally Posted by AaronB

I've just finished fireforming 100 Norma 300wsm cases into 7wsm (against best advice) and about half the cases have a very bright ring at the top of the web. Some also have a bright ring where the old body, shoulder junction was.

The 300wsm cases were sized so that the false shoulder in the neck set zero headspace and the projectiles were lightly jammed into the lands.

I've had case head separation before but that ring was much duller and wider than these rings.

I don't think it's a die mark because none of my Federal 7mm wsm cases have the marking.

To make matters more confusing I sectioned one of the worst offenders and there's absolutely no sign of thinning at the ring (of this case).

Anyone experienced anything like this? I'm gonna have to keep a very close eye on them.

Photo, the colour change above and below the line is also there, not just the camera

You have an oversize chamber and your cases have grown larger at the web to fill the large chamber giving you a bright ring.