Mysterious goo inside new BCG

Well I got a PSA Premium BCG a few weeks back for my first AR.
The BCM upper will be here tomorrow so I decided to clean up and lube up the lower and BCG.

I took the BCG apart and cleaned it up. I removed the bolt and took a chamber mop and mopped the inside of the carrier. When I pulled the mop out I noticed what looked like grease on the very end of the mop. When I touched it it was really sticky, almost like a glue more than grease.
The goo came from the “shelf” inside the carrier, where the rings near the bolt tail would contact the carrier (sorry im new to ARs and dont know the proper terms).

Im worried that it may have been an important substance, I assume that most people totally clean their BCG’s so it doesnt matter, im just curious its purpose if anyone knows.

Just clean it out and go about your business. It’s definitely not an “important substance”, there is no need for heavy grease inside a BC.

Just protective coating for storage. Clean, lube and your GTG.

thanks for the replies.
I was just watching some youtube videos on AR cleaning and lubing.

One guy was using wheel bearing grease on his BCG, it looked about the same sticky consistancy as the stuff in mine.

Not sure why it was in that spot only inside the carrier, but movin on…
Thanks

it was probably cosmoline.

Absolutely. The shiny stuff you see on your new gun is invariably some cheap grease/sticky oil, to keep the gun from rusting before you buy it and nothing more!
Clean it all off and lube it with whatever product(s) you like. Personally on my M4gery i use tetra grease on the sliding parts (auto grease here instead, is fine) and CLP or synthetic motor oil on the rotating. During a shooting session i will give the BCG a couple drops of clp through the two holes. It seems everyone has their own ideas on what is best, and they are probably all fine, so long as your D.I. AR is run wet. I do not use any lubricant with graphite in it, because i have heard it really has an abrasive effect. And probably not needed unless you are at the south pole.

The stuff they ship it with is not a good lubricant.

Look at basic ar15 cleaning sticky in this forum for cleaning and lubing info.

^This…

They’ve been putting cosmoline on weapons ever since Gingus Kahn ordered his first bow and arrow set. It needs to be cleaned and your GTG.