I started using my stash of XM193 and noticed that most of the rounds had this tar-like gunk on the case mouth, with some having it smeared down the case. I assume this is bullet sealant. I'm wondering if one really needs to remove it before using the ammo or not? I found that a quick wipe with Gun Scrubber removes it fine, but it's tedious wiping the ammo down, you know?

So, my question is this: do I really need to spend the effort to wipe it all off, or shoot it?

Maybe a tacked thread with people's experiences with various lots of XM193 would be beneficial; I know I'd have avoided Lot 87, had I known about this...

I have shot lots ( couple thousand ) of XM193 that had bullet sealant on the necks.  They fired just fine. Although they look rather nasty, there is really no reason to clean off the excess sealant on the cases. It is common for XM193 to have sealant on the necks.  I have fired Lot #s 12, 52, 53,and 66. There was smeared sealant on probably10-20% on the rounds.