Hey gang, I realized that when outlining AR-15 anatomy elsewhere on the site we had overlooked the details of the Bolt Carrier Group.

The first thing you’ll notice is that these are available with multiple finish types / coatings:

  • Standard Steel:  Standard issue steel.  These are usually the most inexpensive BCG’s on the market
  • Chrome-Plated: A few benefits come with having a coated BCG.  For one this coating will be resistant to corrosion and other elements that may break down the steel of the BCG.  Some report that chrome plating can chip or flake.  Chrome sits at the mid-price point.
  • Chrome Nitride: I don’t have any solid details on this coating… if someone does, please comment below! 
  • Nickle-Boron: Another type of coating.  I’ve read online that various NiB users do NOT need to lube their BCG at all.  This seems to be a highly debated topic.  NiB is a premium price BCG.
  • Heard of other coating types? Leave a comment below!

I ended up purchasing a Chromed BCG for my AR-15.

While the AR-15 bolt looks confusing, it really isn’t.  You can field strip the bolt using a pair of needle nose pliers which results in the firing pin, and separated bolt, and bolt carrier.  (Video below to for how-to on disassembly).

One point of note: When you re-assemble your bolt carrier group, make sure your bolt is correctly oriented so that the extractor is on the side of the ejection port.  It is possible to insert the bolt in a 180 degree wrong direction.  You’ll figure this out real quickly when your rifle doesn’t eject.  Thankfully this is an easy fix in the field!

Cleaning / Lubrication:

Some folks tend to run their bolt on the dry side.  Others run wet using their favorite firearm lube.  I myself use a thin layer of Mobile 1 grease to lube my BCG.  The bottom line is that your BCG will get dirty, since the gas system is channeling barrel gas into the gas key of your BCG.  There are some cleaning tools out there built specifically for the AR-15 bolt.  Do you have any that you like? Please comment below!

Here’s a cool bolt disassembly video I thought was pretty thorough: