I have a RCBS press and have the full length 5.56 die set. I noticed that when I am depriming and resizing it that I am getting a dent in the shoulder of the brass. I removed the die cleaned it, but it is still happening. This was not happening last time I used it. Any ideas? Thanks.

Maybe Too much lube or die adjusted to deep

Mule,
There is a tiny vent hole through the die body at the shoulder. It may have been clogged from the factory - most are. You can pick it clean with a small sewing needle. One the crud starts to move you can reverse the needle and spin the eye slowly down through the hole. Be very careful not to push a burr up inside the die, scratch the interior or break a the needle off.
I have also used a small paper clip but it is slower. If you have compressed air you can pressurize the die and blow the crud out.
Clean the die before putting it back into use.

Even with the hole cleaned out you have to be very careful with the amount of lube used on the 5.56. A tiny bit too much will cause the shoulder dents that you are getting. A tiny bit too little will cause a stuck case when the rim pulls off.

Let us know what lube you are using and how you apply it.

Too much lube; the bleed holes don't compensate for that. OTOH, dents don't hurt anything; just makes your re-loads look amateurish. Not saying you are, mind you.

There is another possibility: the die may have left the RCBS factory without the bleed hole. I had it happen to me years ago with a .243 die set, and I currently own a set of RCBS dies in 25-'06 that does not have a bleed hole.

If you did get one that doesn't have the vent hole, call RCBS. They will replace it gratis; or at least they did in my situation.

One other suggestion.

Only apply the tinyest bit or no lube to the neck.
Apply NONE to the shoulder. Keep lube away from the slope of the shoulder all together. It does not really need any if the rest is lubed properly.

Apply lube to the case body from the lower corner of the shoulder down.

You guys are unbelievable. I was using to much lube. I'm using Hornady unique case lube. Thanks a lot.