Home AR-15 Ask Ian: Why Does the AR15 Have a Buffer Thingie?

Ask Ian: Why Does the AR15 Have a Buffer Thingie?

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From Arvid on Utreon:
“Why does an AR-15 need a buffer thingy? Why can’t it just have a spring like every other normal gun?”

The Ar-15 really doesn’t need the buffer and tube, but it is a holdover from the origins of the system: the AR-10. The intent of the AR-10 was to create a 7.62x51mm battle rifle that was very lightweight (under 7 pounds, originally) but still soft-shooting and controllable. In order to do that, Eugene Stoner. has to pull out all sorts of tricks. As it applied to our question today, this included a straight-line design with a buffer on the end of the bolt carrier to absorb any residual impact of the bolt carrier on the end of the receiver tube. At this time, there was no apparent need to allow for a folding stock, so the bolt was allowed to run the full length of the stock to minimize felt recoil.

After the basic design was put in place, the disassembly was changed from sliding together to pivoting, and this required splitting the single very long bolt carrier into what we now recognize as the bolt carrier and the buffer. When the design was scaled down to the AR-15, the basic architecture stayed the same, even though the recoil-reducing elements were not really necessary in the new smaller cartridge.

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43 COMMENTS

  1. it is neat how the little barrel extension takes the place of a whole "receiver" technically it should be the "receiver" cause it is what the bolt locks into and it holds the barrel i guess its really like an ak47 trunnion but it has a little flat where a serial number can be visible

    with the buffer what about the bolt carrier bounce that can happen rarely if in full auto the carrier hits the trip releases the hammer and at the same time the bolt carrier slaps into the barrel extension then kicks back a little bit and can unlock it just enough that the hammer hits the bottom of the carrier instead of the firing pin leading the person to think there was a primer failure

  2. Bolt carrier back half… it is just so the receiver can split in half. It is half of the reciprocating mass. it is not a 'buffer' except in an inertial sense. The piece of plastic in the back is a buffer. Miss definition in terms. Not a buffer tube, it is a receiver extension tube. Stop calling it the wrong thing and people will stop being confused. Eugene was an 'engineer' in the worst sense.

  3. 4:48 – funnily enough this is how a lot of early airsoft AEG replicas of AR pattern rifles are taken down because the single-piece hop up unit has to attach to both the barrel and the magazine well to feed BBs into the barrel. Dunno if this is still the case (I haven't played airsoft in well over a decade and I know split level hop ups were a thing at least as far back as like 2007), but it's cool to learn that precedent was actually set all the way back in early designs for the AR-10

  4. Good video. I owned a S & W MP10 and had to send it back to them 3 times. Finally, I had some one look at it and found that they were putting AR15 buffer and spring and in an AR10. I had to send it to them again and they finally fixed it. I did understand wrong parts causes misfires, but now I totally understand.

  5. I don't have an AR but this was very informative. Iv wanted a semi auto AR style platform for quite some time, but I waited so long to decide that that market is flooded with sooooo many parts and makes, I don't even know we're to begin. I would like to build it from the ground up, because I get familiar with things that way, like cars so on. I learn more about how it works and it makes me understand it better.

  6. Mythbusters episode 136 shows a 1911 lighting a strike anywhere match. The slow motion shows the bullet leave the barrel, with the barrel barely rising. Then the slide hits the stop, the barrel flips up. Very enlightening.

  7. I can also attest to 6.8SPC not really needing a buffer. In fact, when I converted mine to use an Adams Arms piston kit, the buffer made it too heavy to cycle properly. I installed a lightweight 2 piece plastic buffer system, which weighs basically nothing, and now it runs smooth like an engine all day long.

  8. Great video, but I would have liked to have seen what you are talking about. Many of us are new to the mechanics of the subject, and I had to go somewhere else to see what parts you were actually discussing. But still… love the information.

  9. I had a green plastic toy rifle (very same as shown in this video illustration) when I was young, being used to Garands and carbines, and even 1903 Springfields as my plastic arsenal, I really didn't understand what that new design was all about, but I knew it looked cool and it probably became a laser gun when needed, boy oh boy would I love to have one of those rifles today, before they're deemed scary and illegal

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