[ Single Feed vs Double Feed Pistols ]
Hi guys thanks for tuning in to another video on ForgottenWeapons.com.
I'm Ian McCollum, and this month we're going to take things a little bit differently,
and instead of having one long Q&A at the end of the month
we're going to split that up into a number of individual single-question videos
that I hopefully can answer in a little bit more depth than I would typically do in a normal Q&A.
So, questions are still all coming from the Patreon and Utreon supporters of Forgotten Weapons,
thanks very much to you guys, you keep Forgotten Weapons going.
And today's question comes from Tyler and he asks, "Why are there so few double-feed handguns?
It seems like the double-feed magazine remediates the worst part of handgun shooting,
which is loading those obnoxiously difficult to load single-feed handgun magazines."
So let's start with a quick definition of what he's referring to.
The idea of double feed versus single feed is referring to
basically when you look at the top of a loaded magazine, how many cartridges do you see?
In more technical terms this would be: how many positions are there
from which a cartridge will feed into the chamber of the firearm?
So in a single-feed magazine, the cartridge at the top of the magazine
is always in exactly the same position.
Even if you have two stacks of cartridges alternating left and right in the magazine,
in a single-feed design when they come to the top
the magazine narrows and that double stack becomes a single stack.
And every cartridge that lifts up to the top of the magazine is presented in the same position.
In a double-feed magazine you will have two stacks of cartridges in the body of the magazine,
and they remain in that configuration right up to the very top.
So that when ... the magazine is actually feeding into the gun
you'll have a situation like this where, say, the right-hand cartridge feeds first.
And then the magazine cycles up one,
and now you've got a cartridge on the left side that's feeding in. And then it goes back to the right.
So in this situation the magazines are easier to load
because you don't have to force one stack of cartridges to split into two,
which has a fair amount of friction to it.
But on the opposite hand, you now have to ensure that
the gun can reliably feed from two different cartridge positions.
So ... first off, let's take a look at
what double-feed handguns we have that are actually out there.
And the one that comes to mind best to me is the Steyr GB.
This was actually submitted to Austrian military handgun trials as a competitor to the Glock 17.
It has an 18 round magazine, and it is double feed.
The HK VP-70 from a similar period also has a double-feed magazine system.
It also has a relatively large capacity.
And then when we get into some of the older guns you'll see this system come around as well.
So I have a Bergmann 1910/21 here that uses a double feed magazine.
Of course the Mauser C96, one of the very first
commercially viable semi-auto pistols, used a double-feed magazine.
Now the C96 did it because the double-feed magazine was Mauser's system.
That's what they had invented, it was one of the core elements of the Mauser rifles
from about this same time period.
And so it makes sense that they would integrate that into their pistols as well.
By the time Bergmann did it the patent on that had expired.
And early on there wasn't necessarily as much nuanced understanding
of what the pros and cons were to some of these different systems.
What we have today is a situation where, yeah, ... you've got pros and cons on both sides,
but they tend to balance out in favour of ... double-feed magazines for rifles,
and single-feed magazines for pistols.
So, the pros to a double-feed system.
The magazines are easier to load, although that's generally not
really considered much by manufacturers.
Definitely not considered much by governments who are looking for military contracts.
You can get a loading tool for your single-feed magazines, no big deal.
But I agree Tyler, it is a lot easier and nicer to load double-feed magazines.
You can get a little bit more capacity in a double-feed system.
Typically I would call it probably 2 extra rounds
because in that single feed magazine (use this one), where you've got this narrowing at the top
you are actually losing a bit of potential capacity.
So if you took that ... conical shape at the top
and you splayed it back open to a pair of straight walls,
you can fit a couple more cartridges in there.
So the Steyr GB has an 18 round magazine, I believe the VP-70 is the same.
Where typical magazines of the period are more like 16, 17 rounds when they're single feed.
Now when it comes to reliability, we have a complicated set of pros and cons going on.
When you're talking about the magazines themselves,
double feed is more reliable than single feed, so let's touch on that real quickly.
Converting from two stacks of cartridges to one, that narrowing process,
that puts a lot of extra friction into the system.
So as the gun fires, as the cartridges move up in the magazine,
they have to jockey for this narrowing from two positions to one.
That's a potential failure point.
And ... the larger capacity the magazine, the worse that gets.
Because the longer the magazine gets,
the more pressure you have to put on the first couple of cartridges
in order to ensure that there's sufficient pressure on the last couple of cartridges.
This wouldn't be the case if you were using a constant force spring,
like one of those wound up springs, but virtually no magazines do that.
We're pretty much always using a traditional coil spring
in the bottom of the magazine pushing down on all the cartridges.
So this, for example, is why Sten gun magazines are
... the worst part of the Sten system in terms of reliability.
You've got 32 rounds of cartridges being jammed through a double to single feed system.
If you just have a plain double-feed magazine,
well both stacks of cartridges can rise up side by side the whole way.
That system is more resistant to a little bit of dirt getting into the magazine,
less likely to cause a problem, and you don't have the extra friction.
So when it comes to the magazines, double feed is better.
... Well, and I should also say: single feed gets worse the bigger the magazine gets.
Now when it comes to the firearms that are actually using these magazines,
single feed is noticeably easier to design for.
And the reason is in a single-feed magazine the cartridge is always presented
in exactly the same place every time.
So you have to design the geometry in your feed system to accommodate one position.
If you have a double-feed magazine, now you need to accommodate
the top cartridge being on the right, or the top cartridge being on the left.
(Right and left from my perspective, not from yours.)
So now you've got twice as much stuff going on.
And remember that the face of the bolt isn't just perfectly symmetrical,
you've got an extractor in there somewhere, you've got an ejector in there somewhere.
Typically the extractor and the ejector are going to be on different sides.
You're going to see in nuance, when you look at this in very slow motion and in detail,
the cartridges do not feed exactly the same way.
And you need to make accommodations in the design to make that work.
It's interesting, I had a chance recently to take a look at one of the prototypes
that led up to the Croatian PHP pistols.
And the early prototypes, before it was called the PHP, actually used a double-feed magazine.
And when they went into full scale production they abandoned that
and narrowed that magazine down to a single-feed system,
simply because it was noticeably less complex
to design the pistol around the single feed position.
Now, there are a couple of other considerations.
So at this point you may be wondering ... like
if double feed is so good, why aren't there more pistols?
And frankly if ... single feed is so much easier to use, why aren't there more single-feed rifles?
Well, there are two additional considerations. The one we already talked about which is that
single feed gets worse the longer the magazine gets.
And that makes single feed tend to be better in pistols where the magazines tend to be shorter.
You don't normally have 30 round magazines in pistols as a standard thing.
Where in rifles (we're talking most of the development here comes from a military perspective),
you absolutely have 30 round magazines as a standard.
And a 30 round single-feed magazine is going to be really difficult
to actually make function on a wide scale.
Not impossible, I know there are examples of it out there, but
it's a lot easier to do it with a double-feed system in a rifle.
The other consideration is size.
If you have a double-feed system it means that the slide of the pistol
has to be wide enough to accommodate ... the cartridges coming off of both sides.
You may notice that a lot of the double-feed pistols out there are rather chunky big pistols.
The Steyr GB being a really good example.
Essentially the slide has to be pretty much the same width as the magazine on the inside.
But ... where the magazine's being held in the grip you generally don't have
really any structural concern, you're not trying to support pressure in there.
You can make that thin and polymer, or thin metal.
When you get into the slide, now you're in an area that's undergoing stress under firing.
And the slide has to be made of stout enough material to withstand that. ...
Now you have to have the inside of the slide a bit wider as well,
that's going to make the whole top end of the gun bigger.
Even the Glock, a fairly notoriously chunky pistol,
is still narrower in the slide by between 5% and 10% than the Steyr GB.
And if you look at modern sub-compact carry pistols
that are designed specifically to be small,
there's no way that you could manage the same narrowness of slide
if you had a double-feed magazine stuck in them.
Now in a rifle that's not an issue at all.
Like the difference of a couple of millimetres in the width of a rifle receiver
to accommodate a double-feed system is irrelevant.
And so that's why we see the single-feed magazines predominate in pistols,
and the double-feed magazines predominate in rifles - the balance of pros and cons.
Hopefully that wasn't completely boring,
hopefully that answered your question fairly well Tyler, thank you for asking.
And we'll be back in a few days with another "Ask Ian" Q&A question.
Thanks for watching.