Cases are denting when going through FL die
Okay I can't figure this out. I've cleaned the die, taken it apart, tried taking the expander out, putting the decapping rod back in (because the cases are already decapped I didn't have it in) and making sure the press rod isn't being deflected. Something is making a dent on the shoulder or just below it. Same pattern, little different in size. I can even feel the pop when a case dents. I don't have anything in the die to make a dent. Its not every case, and the dent is small enough I feel okay shooting these still.
But the hell is causing this?
RCBS FL die #15501
Lee Case lube on a pad
Lee "O" frame press
3x fired Remington Brass
Measured and set the die to bump back the cases 0.002ish.
Measured a few case and they're right about 2.014-2.018 (maybe to long for the die?)
Looks like too much lube.
Looks like too much lube.
I was wondering about that. Didn't think lube would cause a dent though.
It is the air trapped, a bubble causes it.
Don't put any lube on the shoulder or neck, case body only; those dents will pop out when fired.
As to the neck a little lube inside helps.
As mamalukino said, too much lube is the most likely cause. Excessive set-back is another, but it sounds like you've got a lock on that.
It can also be caused by an out of spec die, constricting the cases too much for the chamber you have.
Ditch the lube pad and lee lube. Buy a little tin of imperial sizing wax, apply a super light coating with your fingers. Be happy. :)
I put some water on my pad to thin out the Lee case lube and I'm rolling the bodies only on the pad. So far it seems to be working better.
Along the air bubble line, RCBS dies have a small hole in them, I'm guessing so air doesn't get trapped. But that hole is right behind my lock ring.
I like the Lee lube as it works way better than the Lyman spray crap I have.
If I use the full length dies, I use the Lee lube also, I put a little on each case, avoiding the shoulder and neck, and then roll about 5 at a time between my hands. I then take each case individually and scrape some residue off of my palm into the mouth to lube the expander.
I have the Imperial also but I prefer the Lee.
Try ensuring the vent hole is clear. Buildup tends to clog it preventing the pressure from escaping causing a dent. You said the vent hole is behind the lock ring. I've had the lock nut just over the top of the vent hole and the pressure still vented fine through the clearance in the threads. If the vent hole is in the center to bottom of the lock ring it might restrict flow too much causing too much pressure. Too much lube can also cause dents regardless of how clear the vent hole is.
I bet too much lube as well. Imperial or Hornady unique WAX (not spray) is the way to go. A $5 can will do probably 5,000 cases or more. Just get a little on your finger and it will be enough for 4-5 cases. You don't need enough to see it...just enough to feel slightly slick. Too much and you will get that fancy little dent even with imperial or Unique.
Since it doesn't happen every time, I'm joining the bandwagon and diagnosing excess lube. Take some gun scrubber or carb cleaner (cheaper) and flush out the die. Get a light and inspect. If all good, lube lighter and size some cases. Keep us posted.
As far as lubeing is concerned, if the case feels "slightly greasy" you have enough. Lee lube is good, but the pad application method tends to put too much on if you are not familiar. I will try to describe too much lube...if you hold a lubed case lightly between your pinching fingers and it tends to slide down- you clearly have too much lube. I use the imperial wax and can properly lube three cases with one dip into the wax.
The downside of not enough lube is a stuck case. When you get familiar with your die you will know when the lube is getting short.
Buy a stuck case remover (all loaders should have) just in case.