[ Thompson Mags in the Grease Gun? ]
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 Richard on Patreon, who asks,
"Why didn't the M3 and M3A1 Grease Gun use a double-feed magazine?
And in fact why didn't they just use the Thompson magazine that the US already had?
Seems like that certainly would have simplified logistics."
Makes sense on the surface, so let's start by looking at
the whole purpose, the
It had to be cheap and simple to manufacture,
and the M3 was developed specifically from the example of the British Sten gun.
It's not a copy of the Sten gun, but in terms of industrial production
and design philosophy, the M3 is a very close cousin to the Sten.
It was developed because the Thompson submachine guns,
and even the simplified M1 version of the Thompson,
were very complicated guns to manufacture and very expensive guns to manufacture.
They took a lot of time, they cost a lot of money.
The US wanted a heck of a lot more guns for a lot less money.
And so when they first encountered the Sten gun after the British developed it,
this came across to US Ordnance as an ideal solution.
And what they were looking at was stamped sheet metal, like
... not identical to how the Sten's made, but two ... stamped halves welded together.
Simple blowback, really easy gun to make.
And part of that is also copying the magazine from the Sten gun.
So the Grease Gun essentially uses a .45 calibre version of a Sten gun magazine.
And it is single feed for the same reason that the Sten magazines are single feed.
It's simpler to design the guns to work that way,
and there was in fact a developmental ancestry
between the German MP40s, MP38s, which use a single-feed magazine.
... We can get into that question a little later on, let's stick with the M3 for now.
So we have a single-feed magazine because of that Sten gun lineage.
Now the question is why bother copying the Sten magazine?
If we already have a .45 calibre submachine gun in service, why don't we use its magazine?
And the answer is that essentially you cannot use this magazine
in a stamped sheet-metal manufactured submachine gun.
Why? That's a question that we have to look up close at this magazine to answer.
This is not a Thompson, but this works the way most magazines that we're used to today work.
So we have a magazine well here, and we have a button on the side.
That is just a spring-loaded catch that is going to lock
into a cut in the magazine. In this case, one right there.
So the magazine well is going to hold the magazine in position and in orientation.
And we're just going to slide it in until that catch locks into the hole in the magazine.
This is essentially the system that people have realised
is the most efficient way to do box magazine retention.
And that's the way the Sten gun works, it has a magazine well
that positions and secures the magazine.
And then we have a cutout here that hooks into the magazine catch. Slide it in until it locks.
That is not the way that John Thompson designed his magazine to work.
It's important to remember here that Thompson is basically like
the third ... practical submachine gun to actually be developed and manufactured.
So people didn't have the benefit of the experience that we have today.
Thompson was concerned about making sure that his magazine was held very sturdily in position.
And there are understandable concerns about ...
say, ... just the magazine well being ... a tight enough fit to properly hold the magazine in position
so it doesn't wobble around and change the feed angle, cause problems with feeding.
Or that, say, a simple catch would be strong enough to hold a magazine in position,
say a 30 round magazine full of .45 ACP cartridges that are actually kind of heavy.
And so what Thompson did is he put this big T-shaped lug on the back of the magazine.
Now it's not a milled piece, this is made from a couple of pieces of ... rolled ... sheet steel.
So you can see the side of the magazine on each side comes in and rolls out like a T,
and then there's a cover piece here that's rolled down on top.
And this fits into a matching track
milled into the back of the magazine well in the Thompson gun.
So the Thompson you have to slide the magazine in
all the way at the bottom of the receiver on this rail.
And when it gets to the proper depth, a round plug goes in here to lock it in position.
But that plug just holds it from sliding up or down.
It's this big T-shaped lug that controls the positioning of the magazine
the orientation, and keeps it from bouncing around.
It's interesting to also consider this question in light of
what submachine guns were being manufactured in the US
at the time that the Grease Gun was introduced.
Because not everyone took the same approach.
There were people who looked at it and went, "That does look like a darn good magazine
and we should continue to use it." Referring to the Thompson.
One of these is in fact the M2 submachine gun.
So the ... simplified Thompson was the M1,
and everyone's familiar with the Grease Gun, which is the M3.
There was in fact an M2 submachine gun that came in between,
and it was an attempt to simplify and economise on a submachine gun design.
I actually have a couple of videos on the M2.
It is a fantastically rare gun today because
the manufacturing process hit some real hurdles during the tooling up.
And by the time it was ready to actually put into production
it had been overtaken by the M3 that was a lot cheaper to manufacture.
But the M2 didn't have a milled receiver, it actually had a sintered metal receiver,
but the same solid metal construction instead of sheet metal.
And it did in fact use standard Thompson magazines,
because it would simplify logistics a bit to not have to change that up.
Also you can look at the UD-42, ... the Marlin and United Defense submachine guns.
Those were never really used by the US military because they were in 9mm and not in .45.
But they were manufactured, they were purchased by the US military
to be dropped to resistance organisations and to supply other people in Europe.
And the UD-42 in fact uses basically a 9mm copy of the Thompson submachine gun magazine.
So there ... was a school of thought out there that agreed with you Richard,
that this would be an efficient, good magazine to use.
But look for example at the Reising submachine guns.
These are manufactured with a tube receiver and an eye towards economy again.
And since there isn't a big machined lower on the Reising,
(it's a traditional stocked-looking gun),
it has a little thin sheet-metal bolt-on magazine well.
That's not going to be compatible with this style of magazine retention.
And so Reising came up with his own magazine design, which actually wasn't very good.
It uses a very cheap but kind of clumsy magazine release.
It's a good thing that nobody decided to copy and reuse the Reising mags.
But I thought that's an interesting thing, like there are two sides to a lot of these questions.
Not everything is a really obvious answer, and in this case it is
fundamentally the manufacturing techniques that lead to the magazine design.
So hopefully you guys enjoyed this video.
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Thanks for watching.