What's causing dents in brass

[rcoody]

I would dispose of all that brass.

You have your sizing die set up wrong.

Read a lot about resizing belted magnums before reloading any more

You need the proper tools to measure your shoulder on your fired brass to be able to set your sizing die properly

 

[Laelkhunter]

Try firing a round or two of Factory loads. If it does it with the first round, don't fire the second one and get that rifle to a gunsmith.

 

[Wedgy]

All of the above and add annealing to the list

 

[bigedp51]

IMO, the cracked cases at the web are due to repeatedly over sizing the brass and it finally wore thin and caused a case head separation.

The case head separation caused the big dimples at the shoulders because some of the pressure from the powder burn was lost thru the case head separation. The big dimples at the shoulder are often caused by not having enough pressure to seal the case at the neck and shoulder and it allows some of the gases to come back over the shoulder and makes the dimple.

You need to figure out the why of the case head separation....

Good call Barrelnut. below is a hang fire from surplus Pakistani .303 British ammo during rapid fire mad minute. The bolt was partially opened when the round fired, and this blew the magazine into the ground. And as you can see this caused the front half of the case to collapse when all the pressure vented at the rear of the case. The shooter was not injured other than having to change underwear. The joke with this old ammo was it was "click............................................bang" ammo.

The OP needs to let his cases headspace on the shoulder and not the belt.

Below is a commercial .303 British case stretching and thinning due to long military headspace.

If the cartridge is properly fire formed the first firing it will not stretch and thin. Thereafter you let the case headspace on the shoulder and hold the case next to the bolt face.

The same applies to any type case no matter the type headspace mechanism.

It is the amount of head clearance that causes the case to stretch and thin. And when kept between .001 to .002 of shoulder bump it is well within the elastic limits of the brass. Meaning the case can expand and spring back and not stretch and thin.

 

[johnnyk]

remcraz,

Seen this before on a friends Rem700 in 7mmRUM. The necks are work hardened and letting the gas blow back down between the chamber and the brass. This is a good time to anneal, but if your brass is over worked and soft to begin with its probably toast. Are your primer pockets loose also? JohnnyK.