[ Why Does the AR Have a Buffer Thingie? ]
Hi guys, thanks for tuning in to another "Ask Ian" Q&A on Forgotten Weapons.
I'm Ian McCollum, and our question today comes from Arvid on Utreon.
Arvid asks, "Why does the AR-15 need a buffer thingy?
Why can't it just have a spring like every other normal gun?"
That's an excellent question Arvid, and to answer it we have to go back
to the original design intent not of the AR-15, but of the AR-10.
And in fact not even of that AR-10, not the Dutch
production stuff that actually got into mass production,
but we need to look at the very first early prototypes of the AR-10.
What was Stoner actually trying to do? What was the core element of this rifle?
Well the core element was the idea that the bolt locks into a barrel extension.
Basically the bolt and the barrel are the two pressure containing parts.
Where on a traditional rifle, like say an M1,
your bolt is actually locking into the receiver and the barrel is threaded into the receiver,
and so the receiver is a pressure bearing component.
The receiver has to be very strong, hence the receiver ... is made out of steel.
With the ... Stoner design the receiver can be made out of aluminium,
because it's not actually bearing any pressure.
The bolt locks directly into the back end of the barrel without any intermediary.
So OK, we have an aluminium receiver battle rifle.
What you can get from that, the way you can exploit that,
is to make the whole rifle very light weight.
This makes it handier, easier to carry.
It allows troops to carry more ammunition for the same overall weight, lots of advantages.
And the United States was definitely interested in having a lighter weight service rifle than
the M1, which comes in at about 9.5 pounds.
Well the first trials versions of the AR-10, and we're talking really, really early versions,
came in at like 6.85 pounds, which is ... close to 3 pounds lighter than an M1.
This was close to 3 pounds lighter than the T48 FAL that was being tested.
It was still a good 2 pounds lighter than the M14, that's a really significant advantage.
And if you're going to build a rifle in .308 or 7.62 NATO that's that light,
you're going to have to pull out every trick in the book to make sure that it's actually controllable.
I mean sure you can make it really light easily,
and then it becomes nigh impossible to shoot rapidly in semi-auto, much less in full-auto.
And Stoner did in fact pull out every trick in the book - and spoiler - it worked.
The early, early AR-10s are exceptionally controllable rifles
despite being very lightweight, because of all these tricks.
Now the rifle would become heavier over time.
This is about as chunky and fat as the AR-10 got, the Portuguese contract.
But let's look at what Stoner did to make this happen.
Well the first, and perhaps the most important thing,
is to design a rifle where the recoil runs in a straight line directly into the shooter's shoulder.
You can see on the AR you've got the barrel goes straight into the buttstock.
The buttstock connects to the shoulder.
When you fire the rifle it's going to recoil straight back,
it's not going to have a moment that pushes the barrel up.
If we look at the geometry on an M1, the barrel is right about here.
It's actually above the toe of the stock, and so when this pushes back
if it's pushing this way and it's being restrained here, it's going to tip up.
The muzzle's going to climb with each shot simply because of physics.
Yes, you can put in some effort and hold it down.
But what you want is a rifle that you don't have to hold down.
So that's the first thing that Stoner does.
This gives him a long receiver tube that he can fill up with his bolt carrier,
and it can travel straight back into the stock.
At this point in time there was no apparent conceived need
for a folding or collapsing stock on a standard infantry rifle.
If we look at what the United States was testing at that time
which would be the M1 as the control, and then the AR-10,
the FAL in the guise of the T48,
and what would become the M14. These are all solid-stocked rifles.
And there's really no plan out there, like, "We don't need a folding stock."
So that's a compromise that can be very easily made on Stoner's design.
The stock can be considered a fixed part of the receiver.
So the next thing he does is add a buffer to the end of the bolt carrier.
At this point, and we're talking the very, very early prototypes,
there's actually a picture in the Collector Grade book about the AR-10 of serial number X03.
Where, first off, the receiver design was different than this.
The receiver, instead of pivoting on a pin at the front,
instead it has a pair of rails and the lower actually slides onto the upper.
So to take it apart, you slide the two pieces laterally apart.
What this meant was the bolt carrier could be a single long piece,
and it was quite long, and it incorporated
both what we recognise today as the bolt carrier,
and also what we would call the buffer.
Now the end of the buffer was able to absorb ... whatever last bit of impact there might be
when the bolt carrier hit the very end of what we would today call the buffer tube,
when it hits the end of the receiver or the receiver extension.
That impact is also very important for controllability in a firearm.
What we see, and this is really obvious in slow motion footage, is the muzzle climbs
like significantly, dramatically, very visibly,
when the bolt hits the back of the receiver and comes to an abrupt stop.
It's transferring energy into the rifle, which especially in a ... traditional gun
like an M1 or an M14 where the stock is not directly in line with the barrel,
when you get an impact of the [bolt] going backward, that pops the muzzle upward.
So between the straight line geometry and having a buffer to absorb that last bit of energy,
the AR-10 is in fact a fantastically controllable rifle.
... The only thing that I could even come close to comparing the AR-10 to
in a 7.62 NATO calibre rifle, full or semi-auto, would be the FG-42.
And the FG-42 is a more fragile rifle, I would say, than the AR-10.
So that's why the buffer exists in the first place.
Now as development progresses on the AR-10, there's a substantial change
made to the way the gun is actually assembled.
And that's to replace this pair of sliding rails with two pins.
And the idea is you can remove the rear pin of the rifle, and then pivot the gun open.
When you do that you have access to the bolt carrier for disassembly,
but it's a much easier process than sliding both of the receiver parts apart.
And you also get this cool benefit of now the spring is captive inside the buttstock,
and doesn't actually have to come out of the gun when you do a field strip.
I think that's something that we've got so used to that we
don't tend to recognise that it's kind of unique and special.
Consider virtually any other semi-auto rifle that you disassemble.
When you pull out the bolt carrier, you're also pulling out the recoil spring with it.
But not on an AR pattern rifle, the recoil spring is contained in the buttstock.
This makes a lot of sense, ... like the spring doesn't need to be cleaned, the spring's not getting dirty.
Unless you have to take it out every time, and then I don't know about you guys,
but here in the desert if you pull out a recoil spring
it's almost always going to have some oil on it somewhere.
You set that down on, say, sandy ground it's going to pick up a bunch of sand,
and now you're maybe creating a problem when you reassemble the rifle.
If you're going to leave the spring in the buttstock, fantastic, that simplifies the whole process.
Well, when they go to make this change to a two-pin pivoting disassembly,
Stoner can no longer leave the bolt carrier as one long continuous piece
because it's too long, the bolt carrier is reaching into the stock when the bolt is fully forward.
So what he does is split it into two pieces.
And that's where we get what we would recognise as the bolt carrier today, and the buffer.
When the gun's assembled and operating,
those two parts essentially work as one contiguous weight.
It's the mass of that piece that provides part of the delay for the system opening.
And so essentially the reason that the AR-15 has a buffer today
is because it has a pretty darn long receiver tube and bolt carrier assembly
because a folding stock was not a necessity of the design from the beginning.
A folding stock is a feature that was sacrificed
in order to make the gun controllable despite being very light weight.
Now if you fast forward to today, the vast, vast majority of ARs out there are not AR-10s,
they are AR-15 derivatives in 5.56, where a lot of these tricks just aren't nearly as necessary.
There's less energy in the 5.56 cartridge obviously.
The bolt ... has less energy when it's coming back, it's a lot easier to control the bolt.
You don't need quite as much special fancy effort to make a 5.56 rifle controllable as a 7.62 one.
In addition, many of the ARs on the market today, even in 5.56,
still weigh more than those very early trials AR-10s.
So that's why we see a lot of modern rifles, particularly in 5.56,
... like shortening the whole thing.
They can go to just a spring, or a pair of springs,
that are say mounted above the chamber, above the action, to act as recoil springs.
With Stoner's design, with the AR, this basic system where ... the bolt carrier is one long tube
that extends into the buttstock, that gets set pretty early in design.
And by the time it gets to the point where people are thinking,
"Well, maybe it'd be nice to have a folding stock and shorten this all up."
Well, you've done a lot of iteration and a lot of engineering development
on the system as it exists, and that's a pretty substantial change to make.
And what ultimately happens is Colt doesn't make that change with the AR.
They leave it as is, they design a collapsing stock where they
shorten up the ... buffer tube a little bit so that you can collapse the stock in.
And that's good enough for what the US Army wants.
And then it's left to other manufacturers to design other systems from the ground up
without making that compromise that sacrifices the ability to have a folding stock.
So if the AR-15 was being designed from scratch,
would it need to have a buffer tube like it does today?
No it wouldn't, largely because it's not in 7.62 NATO.
And that's why ... you see virtually no rifles in 5.56
that need to have something like that buffer tube.
So yes, engineering development, design of rifles has advanced such that
yes, there are plenty of .308 calibre rifles today that don't need a buffer tube system either.
But I would argue that even some of those have a hard time competing
with the controllability of the very early AR-10s.
Anyway, hopefully that was an interesting answer, I think this is a neat bit of design history.
If you would like to have your own question answered in a video format like this,
please head on over to Patreon or Utreon. I have threads on both of those platforms
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Thanks for watching.