CMMG GUARD 9mm beating up brass

[ProfessorGascan]

Any Guard owners notice that the barrel extension leaves two large gouges on brass from extraction?

 

I was loading a batch of freshly tumbled cases and got half a dozed split cases after the belling station on the press. They all split right along the scratch/score marks on the brass.

 

Has anyone sanded or filed the specific lugs of the barrel extension to knock the sharp edges off? 

[Les Snyder]

I do not have a complete CMMG carbine, it is a NFA lower and upper with CMMG RDB bolt and barrel.. the scratches from my rifle are from the bottom teeth of the bolt as they cycle over the next to be chambered cartridge while cartridge is still in the magazine... I leave my brass on the ground as a courtesy to the squad to keep the match moving... I buy reclaimed brass from the range, so eventually I'll get some back... at this time, it is cosmetic only

[RickT]

Is this a Glock Guard or Endomag Guard?  I've never seen it with Glock mags in my older Guard.  With my AR Guard the rounds will get a scratch and retracting the bolt over a fully loaded mag will put a pretty good scratch on the top round, but I don't notice much when I load full mags on an open bolt.

[ProfessorGascan]

I use both a guard glock lower and a regular ar lower with endomags.  The marks are definitely from extraction as the scratch marks go through the soot on a fired case.