However, for those of you who aren't as fortunate, I thought I would put together this guide to show what different parts of the AR15 look like at different round counts. Hopefully this information will help you estimate the amount of wear and tear left in a used rifle. First some important caveats: The AR15 is a very modular system. You can replace virtually any part in it with a brand new part very easily. As a result, just because one part is brand new doesn't necessarily mean the rest of the rifle is in the same condition. This guide concentrates on the bolt carrier group. This is for two reasons - one is that the bolt carrier group is a part that is critical to the function of any AR15, two is that the bolt carrier group is like the rings on a tree - it is one of the best ways to figure out the wear on an AR15. This is not an exact science. Using different lubrication, different amounts of lubrication or shooting under different conditions may cause you to have similar wear but with significantly less/more round count than the pictures here. However one thing that does remain constant is these pictures give you a good idea of wear on these parts over time and a rough idea of how much use remains in the part. ============================================== How to determine the round count on an AR15: We will start from the outside of the bolt carrier group and work inwards. Key parts to examine on the bolt carrier group are the bearing rails (particularly the front and rear of the rails), the underside of the bolt where the hammer drags, and the front edge of the base of the gas key. These are areas where wear will show first. The shinier these areas are and the further the wear extends towards the center of the bolt carrier, the more rounds have been fired with that bolt carrier. One nice thing about the bearing rails of the BCG is that they serve as a rough guide from 0 rounds to 10,000 rounds. At 10,000+ rounds, much of the finish will be gone from these rails and they will be shiny and polished. Bolt carrier group w/ 276 rounds vs. Bolt carrier group w/1,849 rounds Note how the 276 bolt carrier has just a tiny spot of wear on the front of the rail and at the top corner of the base of the gas key. Also head of the 276 cam pin has just a few scratches in the finish; but still has a lot of finish. In contrast the 1,849 bolt carrier group is missing most of the park from the front section of the rail, has more finish wear at the base of the gas key and more finish wear on the head of the cam pin. Examples (Hi-Res): Bolt Carrier Group with 276 rounds, Bolt Carrier Group with 315 rounds, Bolt Carrier Group with 1,849 rounds While it is less reliable, you can also look at hammer wear on the underside of the bolt in order to get a rough guess of the round count. However, bolt carrier groups will typically not show substantial wear from the hammer until after the 2k mark. This picture shows (from front to back) 1,849 rounds, 276 rounds, and 315 rounds: ============================================== Even better than examining the bolt carrier, is examining the bolt itself and the cam pin. The shinier the cam pin and the more obvious the "groove" in the pin, the more rounds that cam pin has seen. On the bolt, you are looking at three areas - the ring right behind the extractor cut, the tail of bolt behind the gas ring, and the bolt face. The ring behind the extractor cut bears on the inside of the bolt carrier and is one of the first places to show wear. The less parkerizing you see here, the more rounds through the gun. Likewise, the tail of the bolt behind the gas rings gives two signs of wear - first the parkerizing wears off the tail from hot gases flowing around it. Second, over time carbon that is very difficult to remove begins to build up even with dedicated cleaning efforts. The carbon buildup can be a misleading indicator though since it depends on the cleaning habits of the shooter, type of firing done, and once it reaches a certain point it becomes self-limiting and a bolt with 12k rounds will look much like a bolt with 6k rounds. However, when a seller is claiming less than 1,000 rounds and you notice significant carbon build-up, that is a good sign of bad maintenance habits or more shooting than claimed. Let's look at some examples: Here is what a brand new, never fired bolt looks like (Hi-Res) for comparison (keep in mind that a bolt in this condition may also indicate a potential problem - the gun has never been fired with this bolt): Bolt with 276 rounds Hi-Res: Note that this bolt has just a tiny bit of wear on around the leading edge of the ring, almost no wear on the tail and just a tiny bit of carbon buildup from lax cleaning o ). The cam pin shows wear at the bottom, on the edges of the top of the pin and around the groove. Bolt with 295 rounds Hi-Res: Very similar to the previous example; but with a bit more wear on the tail and less even wear on the ring. Bolt with 315 rounds Hi-Res: Wear on the cam pin is not much different; but there is noticeably more wear on both the ring and the tail of the bolt as well as more carbon build-up. This bolt was run fairly dry and you can see the difference in the wear. Bolt with 1,849 rounds Hi-Res: By comparison, even though this bolt has five times as many rounds on it, it has been kept drenched in Slip 2000 gun lube and is in better shape than the 315 bolt. With one major difference being that although this picture doesn't show it well, there is significantly more carbon built up on the tail of the bolt. PLACEHOLDER FOR 4k+ PICS As you can tell, even with a significant difference in the round count, it can be tricky business trying to guess the difference between a well-maintained bolt with 1,500 rounds on it and a poorly maintained bolt with 300 rounds on it; but what about that bolt face business? Well, the bolt face is probably the single best place to see small differences in round counts on low round count guns, however as round counts increase, it becomes less useful. Let's take a look at a new, never fired bolt face Hi-Res: As you can see, the bolt face itself is black as night. There is no wear on the ejector pin and no wear at all on the face of the lugs. No powder residue, no sealant, no brass marks - completely new. Bolt face w/ 276 rounds Hi-Res: Still pretty good here - all of the parkerizing is still on the face of the bolt; but we have a little leftover primer sealant and powder residue on the face as well. Also, the ejector and the face of the bolt lugs are missing some parkerizing; but all in all, pretty good condition. Bolt face w/ 295 rounds Hi-Res: Pretty much the same, with a little less wear on the face of the lugs and a different pattern of wear on the ejector. Also more sealant and powder residue around the bolt. You can also see a small ring starting to form around the firing pin hole. This ring will start to form around 300 rounds and becomes more pronounced over time. Bolt face w/315 rounds Hi-Res: Once again, similar to the other examples except we begin to see some wear on the actual bolt face and the ring around the firing pin hole is more clear. Bolt face w/1,849 rounds Hi-Res: Remember how it was more difficult to tell the 1,849 bolt from the 315 bolt? Not so difficult now is it? The 1,849 bolt is missing most of the park from the bolt face and has an even, shiny pattern of wear on the lugs and ejector. Further the ring is fully formed now and probably won't look much different at twice this round count. PLACEHOLDER FOR 4k+ PICS As you can see, estimating the round count on an AR15 involves knowing what parts to check. For a low round count gun that hasn't had time to develop wear on the bigger parts, the bolt and bolt face will be critical in determining the round count. As the gun starts to get a higher round count, there will be less difference between a bolt with 7k rounds and a bolt with 5k rounds. At that point, you will want to start examining the bolt carrier group more, looking particularly at the areas we covered. The less finish you see in those areas, the higher the round count. No finish at all and a bright shiny polished surface means quite a few rounds. Hopefully this guide was helpful to you in evaluating your used AR purchase. For those of you who have an accurate round count on your weapons, please feel free to share your own pics of the bolt, bolt face, cam pin and bolt carrier group. Hopefully, this will make a better resource for all of us.