75mm vs 76mm Gun
k...@ogre-ltd.com
Division History series written after WWII about my Dad's outfit, the 5th
Armored Division. It was primarily written for the men that fought in the
unit and not for someone trying to learn about it 55 years later, it that
a fairly high level of knowledge about some technical things is assumed. I
have two questions I hope someone might can help me with.
1. From this and other books, I learned that Sherman M-4 tanks were
equipped with both 75mm and 76mm guns. I may be wrong, but I think the
barrel on the 76mm was much longer than that on the 75mm. I know there
must be a bigger difference than the "one silly millimeter" in the
diameter of the barrel, and I think the 76mm was introduced later in the
war. Did the 76mm fire a more powerful shell? Did it have greater armor
piercing capability? Could the 76mm also fire 75mm rounds the way a .357
magnum pistol can fire .38 special rounds?
2. A paragraph I read last night talked about returning fire with 75mm
rifles and 75mm guns. What is the difference? I always thought that a gun
was smooth bore (i.e., a shotgun) and a rifle had rifling down the barrel.
I assume there could no longer be such a thing as a smooth bore artillery
in WWII, so what's the deal? The way it was worded seemed to make it
clear they were different.
As an aside, I noted that throughout the book, jeeps were referred to as
"peeps." Wonder why?
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DBSDESIGN
> I have been re-reading "Paths of Armor", which is one of the U.S. Army
> Division History series written after WWII about my Dad's outfit, the
> 5th Armored Division. It was primarily written for the men that fought
> in the unit and not for someone trying to learn about it 55 years later,
> it that a fairly high level of knowledge about some technical things is
> assumed. I have two questions I hope someone might can help me with.
> 1. From this and other books, I learned that Sherman M-4 tanks were
> equipped with both 75mm and 76mm guns. I may be wrong, but I think
> the barrel on the 76mm was much longer than that on the 75mm.
Yes. The barrel of the 76mm was intended to be even longer when
it was first tested. It was shortened in length for production, but
it was still much longer than the stubby 75mm gun.
> there must be a bigger difference than the "one silly millimeter"
> in the diameter of the barrel
Not much. I think the diameter of the 76mm was actually 76.2mm.
> and I think the 76mm was introduced later in the war.
Yes. First examples in the ETO arrived late in the Normandy invasion
but unfortunately very few Shermans had a 76mm at that time. The
same 76mm gun was mounted on the M-18 "Hellcat" Tank Destroyer,
which also arrived in Normandy at about the same time.
> Did the 76mm fire a more powerful shell? Did it have greater armor
> piercing capability?
Much better than the 75. Although the standard anti-tank round
(called APC) left a lot to be desired. A tungsten core anti-tank
round was developed (called HVAP) which had a much higher
muzzle velocity and penetrating power than the older APC shot.
HVAP tungsten core rounds were available after the Normandy
campaign, but never in large quantities. Some US tank crews
complained about this and for good reason. They were tired of
watching the standard 76mm APC shot bounce off Panthers and
Tigers on a regular basis. It was frustrating and un-nerving.
Note that the 76mm gun installed in the Sherman is sometimes
confused with the much older 76mm naval gun mounted in the
M-10 Tank Destroyer. The naval gun was usually referred to as
the "3-inch". The new 76mm was actually intended to be more
powerful than the old 3-inch, but as it turned out, both guns had
identical penetrating power. This left many people angry with
the ordnance dept. since the new 76mm gun didn't improve upon
the 3-inch in hitting power as promised. Bradley and Eisenhower
were extremely upset with US Army Ordnance over this issue.
The new 76mm gun was however, considerably lighter than the
3-inch naval gun. That was about the only meaningful advantage
of the 76mm over the 3-inch. The new gun may have had better
target ranging and sighting equipment but I'm not certain of this.
Perhaps someone else in the group can explain any differences
in sighting gear between the M1A1 76mm and the 3-inch gun.
_____________________________________________________
D B S D E
S I G N @ a o l. c o m
_____________________________________________________
...All I ask is a tall ship and a star to steer her by... - John Masefield
Hillbrath
>> there must be a bigger difference than the "one silly millimeter"
>> in the diameter of the barrel
>
>Not much. I think the diameter of the 76mm was actually 76.2mm.
There was no difference in the diameter, at all. The name change was intended
to reduce confusion. I am not sure how confused we would have been otherwise,
but, there is still a lot of confusion. The U. S. 3 inch and the British 17
pounder and 77mm are also the same size.
[snip]
>Note that the 76mm gun installed in the Sherman is sometimes
>confused with the much older 76mm naval gun mounted in the
>M-10 Tank Destroyer. The naval gun was usually referred to as
>the "3-inch".
I could well be one of those that is confused, because I think that some M10s
had the 3inch and some the 76mm.
> The new 76mm was actually intended to be more
>powerful than the old 3-inch, but as it turned out, both guns had
>identical penetrating power.
This was not a coincidence. When it became clear that the 76 was not going to
come up to the expectations, the final load was selected so that performance
was identical.
I don't have a "cite" but, I am sure that the problem with the 76mm was bore
life. When it was loaded to "hotter" specs, it erroded the bores faster than
the requrements. So, there was some flexibility in selecting the final load.
>This left many people angry with
>the ordnance dept. since the new 76mm gun didn't improve upon
>the 3-inch in hitting power as promised. Bradley and Eisenhower
>were extremely upset with US Army Ordnance over this issue.
US Army Ordnance wasn't just totally pleased with Bradley and Ike, either. But,
there is no doubt that Ordnance over hyped the 76.
>
>The new 76mm gun was however, considerably lighter than the
>3-inch naval gun. That was about the only meaningful advantage
>of the 76mm over the 3-inch.
I think there were two major reasons for the development of the 76. The first
was that the original idea of the 3 inch was to use tubes that were already
available which had been built for Naval AA guns which the Navy decided they
didn't want.
But, after some guns had been built and tested, it turned out that there were
no existing tubes, at least, not enough. That really got the Army upset, they
didn't want to be involved with the Navy to start with. Then some tubes were
found, but, there was still some ill feeling and desire for an all Army
solution.
The second reason was that the 3 inch was a typical design for a shipboard gun,
which meant that it had entirely too much recoil stroke for a tank. The version
in the M10 had a considerably shortened stroke, but, it was still too long to
go in an M4 turret. So, the 76 was designed to have a shorter stroke still.
In addition to the 3 inch guns that went into the M10, there were also a lot of
them used as towed AT guns. Probably about as many as in the TDs.
Ian Hogg, in at least one of his many books states that the U. S. never
deployed a towed AT gun bigger than the 57mm (based on the British 6 pounder.
well, identical to the 6 pounder, almost.) There was also a towed version of
the 90mm, which was not deployed. By then, no one wanted an AT gun that
couldn't move itself.
> The new gun may have had better
>target ranging and sighting equipment but I'm not certain of this.
Sorry, I don't know anything about that.
[snip]
Henry Hillbrath
David Alexander
k...@ogre-ltd.com wrote in message <7a48ss$p...@dgs.dgsys.com>...
>1. From this and other books, I learned that Sherman M-4 tanks were
>equipped with both 75mm and 76mm guns. I may be wrong, but I think the
>must be a bigger difference than the "one silly millimeter" in the
>war. Did the 76mm fire a more powerful shell? Did it have greater armor
>piercing capability? Could the 76mm also fire 75mm rounds the way a .357
>magnum pistol can fire .38 special rounds?
The 75 was designed to fire a high-explosive rather than AP shell. It had a
lower muzzle velocity, and was intended to be used more as an artillery
piece than for defeating armor. This was consistent with Army tactical
philosophy which did not foresee the Sherman slugging it out with enemy
tanks. That was what tank destroyers were for, but as we all know, in
practice it turned out that the best TD was another tank.
I've never read that the ammo was cross-compatible, and I would doubt it.
>
>2. A paragraph I read last night talked about returning fire with 75mm
>rifles and 75mm guns. What is the difference? I always thought that a gun
>was smooth bore (i.e., a shotgun) and a rifle had rifling down the barrel.
>I assume there could no longer be such a thing as a smooth bore artillery
>in WWII, so what's the deal? The way it was worded seemed to make it
>clear they were different.
What was the date of the action described? Early in the war, the Army still
had a lot of towed WWI-era French 75s, although I don't recall that they
were ever used extensively in combat. Other than that, the only 75mm in the
US arsenal that I am aware of offhand was the Sherman's main gun. The
reference could be a way of distinguishing the Sherman gun and the towed
gun. More likely, it is a reference to Shermans equipped with
short-barrelled and long-barrelled rifled versions of the 75 intended to
increase its tank-killing power. This is a guess; surely someone out there
with references at hand can clear this up?
>
>As an aside, I noted that throughout the book, jeeps were referred to as
>"peeps." Wonder why?
According to Geoffrey Perret's book "There's a War to be Won," soldiers
preferred to call it a "peep" throughout the war. Willys' preferred
designation, "jeep," won out among the civilian population because it was
heavily promoted.
The word "jeep" came from a comic strip or cartoon character (Popeye had a
magical doglike critter he called The Jeep) or was a contraction of GP (for
General Purpose), depending on which source you read. Probably, it was
both.
As to where "peep" came from, I'm sure someone in this group can answer
that.
Damien Fox
David Alexander wrote in message <7aaehk$h...@dgs.dgsys.com>...
>snip<
Could the 76mm also fire 75mm rounds the way a .357
>>magnum pistol can fire .38 special rounds?
>snip<
>I've never read that the ammo was cross-compatible, and I would doubt it.
It was not, and that was the reason for the nomenclature difference- the
shells have SIMILAR dimensions, and a confused or ignorant soldier might
force a round from one into the other.
>>2. A paragraph I read last night talked about returning fire with 75mm
>>rifles and 75mm guns. What is the difference? I always thought that a gun
>>was smooth bore (i.e., a shotgun) and a rifle had rifling down the barrel.
>>I assume there could no longer be such a thing as a smooth bore artillery
>>in WWII, so what's the deal? The way it was worded seemed to make it
>>clear they were different.
>What was the date of the action described? Early in the war, the Army
>still had a lot of towed WWI-era French 75s, although I don't recall that
>they were ever used extensively in combat. Other than that, the only
>75mm in the US arsenal that I am aware of offhand was the Sherman's main
>gun. The reference could be a way of distinguishing the Sherman gun and
>the towed gun. More likely, it is a reference to Shermans equipped with
>short-barrelled and long-barrelled rifled versions of the 75 intended to
>increase its tank-killing power. This is a guess; surely someone out
>there with references at hand can clear this up?
Well, actually, the US used quite a lot of 75mm weaponry. Off the top of my
head:
75mm Cannon (nomenclature unknown)- used by the M-3 Grant/Lee- this weapon
was different from any other 75mm weapon in the US arsenal
75mm Cannon (nomenclature unknown)- as used by the SHerman. Slightly longer
75mm Cannon (nomenclature unknown)- entirely new design, used by the M-24
Chaffee light tank.
75mm Howitzer M-1 used as a pack howitzer, SP in the cannon company of an
infantry regiment in North Africa, and later as the armament of the M-8HMC
and LVT (A)4. Note that traditionally, howitzers are called "guns" by the
artillery, so this might be what was referred to above.
75mm M1897A2 Cannon- the old French Vingt-cinq. Used as field artillery, and
SP artillery/AT, early in the war.
75mm Recoiless Rifle M-2. Another possible expalnation for the above quote.
76mm (3 Inch) Gun M-3- An early-war AA piece
76mm (3 Inch) Gun M-5- a towed AT gun, also referred to as a towed Tank
Destroyer
76mm (3 Inch) Gun M-7- ex-AA weapon in the M-10 SP tank destroyer
76mm Gun (nomenclature unknown)- used by the Sherman and M-18 tank destroyer
Finally- the bazooka was referred to by many people as "the shoulder 75."
Hope this helps
Damien Fox
DBSDESIGN
<dbsd...@aol.com> wrote:
>> the 76mm gun installed in the Sherman is sometimes confused
>> with the much older 76mm naval gun mounted in the M-10 Tank
>> Destroyer. The naval gun was usually referred to as the "3-inch"
> I could well be one of those that is confused, because I think that
> some M10s had the 3inch and some the 76mm.
There was the T72 project, (M-10 with 76mm instead of 3-inch)
The gun change and a new turret was expected to solve the balance
problems caused by the heavy 3-inch gun, and to lighten the M-10
overall by about three tons. I don't know if the T72 M-10 ever went
beyond the prototype stages. The project was cancelled after the
M-18 Hellcat was approved for production. Good decision I think.
>> The new 76mm was actually intended to be more powerful than
>> the old 3-inch, but as it turned out, both guns had identical
>> penetrating power.
> This was not a coincidence. When it became clear that the 76 was not
> going to come up to the expectations, the final load was selected so
> that performance was identical.
I didn't know that. I guess this also had to do with keeping the bore
wear and gun barrel changes on a standard schedule for both guns?
> I don't have a "cite" but, I am sure that the problem with the 76mm
> was bore life. When it was loaded to "hotter" specs, it erroded the
> bores faster than the requrements.
I'm curious, do you know why the British were able to push muzzle
velocity over 3,900 feet per second on the best 17-pounder round?
That's quite a bit higher than the U.S. HVAP round which was 3,400
fps on 76mm and 3-inch, and about 3,350 fps for U.S. 90mm HVAP.
Was the British Army less critical about gun barrel replacement
schedules, or was the higher velocity possible because the round
worked differently than HVAP?
> In addition to the 3 inch guns that went into the M10, there were
> also a lot of them used as towed AT guns. Probably about as many
> as in the TDs.
I don't know how many TD battalions had them, but I've read that
the 3-inch gun wasn't very popular on towed mounts because of
its massive weight.
They should have put the new 76mm on a towed mount to replace
the 3-inch, which was almost twice as heavy as the 76 and very
difficult to manhandle into position, even by a crew of four men.
I've seen photos of guys struggling to push 3-inch guns around in
the mud and snow of the Ardennes. Not much fun. In contrast, the
76mm on a towed mount could have been light enough to be landed
by U.S. Airborne troops and pulled by a jeep instead of a truck or
a half-track, which the 3-inch gun required.
_____________________________________________________
D B S D E S I G N @
a o l. c o m
_____________________________________________________
William Prince : "Wait a minute, what if my 'chute doesn't open"?
Errol Flynn : "You'll be the first one on the ground".
- Objective, Burma! 1945 -
drwatcher
> Early in the war, the Army still had a lot of towed WWI-era French 75s, although I
>don't recall that they were ever used extensively in combat. Other than that, the
>only 75mm in the US arsenal that I am aware of offhand was the Sherman's main gun.
>The reference could be a way of distinguishing the Sherman gun and the towed gun.
DOH! Of course there were other 75s out there! Little 75 mm pack howitzers and
field pieces that infantry battallions carted around by the hundreds. These are
surely what the writer was referring to. (Forgive me. It was Monday)
DBSDESIGN
> If I remember correctly, the old 75 on the Sherman was a French
> design of 1917 ordered for manufacture in the US and for which
> the tools still existed in 1942.
The 75mm gun installed in the Lee, Grant and Sherman was broadly
based on the French 75 from WW1, but was still a new design with
new tooling. The new 75mm gun was first designated M2, and later
M3, by the US Army.
However, the US Army had a large supply of French 75mm guns left
over from from WW1. The French 75mm was designated M1897A3
by the US Army (but just to make things confusing, the French gun
was designated M4 75mm by the USAAF). The Army used the French
gun in WW2 by mounting it on a half-track and trying to use it as
a tank destroyer. Although the US Marine Corps used this vehicle
successfully for bunker busting, a thin-skinned half-track didn't
work very well against tanks or other heavily armored vehicles.
The Air Force had some success with the French gun by mounting
it in the nose of a B-25 bomber, using the gun for anti-shipping
operations, among other things. The 75mm cannon worked better
than expected in an airplane. The first real gunship in the USAAF.
Then the US Navy got into the act. One of the PT boat squadrons in
the South Pacific acquired an M4 75mm cannon from the USAAF,
probably salvaged from a wrecked B-25. This was not unusual as
the Navy PT service was in the habit of taking M4 37mm guns from
wrecked P-39 fighters. It made for a great lightweight deck gun.
Anyway the PT ordnance people mounted the 75mm gun on the stern
of PT 334 and tested it in April 1944. The crew reported that the gun
worked well against surface targets, but the 75mm had no provision
for automatic tracer control. This was important to PT boat crews
since they mainly worked at night. There was also a possibility that
the recoil stroke of the 75mm might damage the wooden decks, so
the idea of using the French 75 as a deck gun on PTs was dropped in
favor of the more versatile and common 40mm Bofors.
All in all, the US military establishment certainly got a lot
of mileage out of the ancient M1897 French 75mm field gun,
in two world wars, no less. :-)
Hillbrath
>I don't know how many TD battalions had them, but I've read that
>the 3-inch gun wasn't very popular on towed mounts because of
>its massive weight.
>
Hey, I was looking for something else, and I found a number!
1500
That is in the Green book "Tiger Tank", ISBN 0-87938-954-0
Henry Hillbrath
Hillbrath
>>(Hillbrath) wrote:
>
><dbsd...@aol.com> wrote:
[snip]
>
>> This was not a coincidence. When it became clear that the 76 was not
>> going to come up to the expectations, the final load was selected so
>> that performance was identical.
>
>I didn't know that. I guess this also had to do with keeping the bore
>wear and gun barrel changes on a standard schedule for both guns?
Well, that is a surmise on my part, but, I can't imagine developing a brand new
gun and having it turn out exactly the same as the old one by accident.
Two different gun designs may not have exactly the same life, even with the
same performance.
>
>> I don't have a "cite" but, I am sure that the problem with the 76mm
>> was bore life. When it was loaded to "hotter" specs, it erroded the
>> bores faster than the requrements.
>
>I'm curious, do you know why the British were able to push muzzle
>velocity over 3,900 feet per second on the best 17-pounder round?
>That's quite a bit higher than the U.S. HVAP round which was 3,400
>fps on 76mm and 3-inch, and about 3,350 fps for U.S. 90mm HVAP.
>Was the British Army less critical about gun barrel replacement
>schedules, or was the higher velocity possible because the round
>worked differently than HVAP?
There is no difference in internal ballistics between HVAP and HVAP-DS (APDS).
How does the bore know if the sabot is going to come off after it is outside?
When I was a the Ordnance School (1960), somehow the subject of bore life came
up in the discussion. At least one of the instructors, I think maybe more than
one at different times, looked sort of like he was selling Fench postcards, or
some other activity that he didn't want everyone to know about, but, seemed to
feel that we should know.
In short, the story was that "a long time ago" there was a great contoversy
about bore life. Some stuck firmly by the specification, which I think was 400
rounds. Others though that this was a "War Emergency" situation, and that the
tankers should be given every edge that they could possibly be given. After
all, how many HVAP rounds are you going to fire through one tube, anyway.
Especially since there was a shortage of HVAP.
The "strict constructionalists" won, but, it seemed that hard feelings
persisted a long time afterward.
I though at the time they were talking about Korea. I didn't know then that
there *was* HVAP in WW II.
But, later on, in learning about the great controversy over the 76, I have the
"gut feel" that it was the souce of the story.
There are two main ways that you can increase the velocity of a projectile in a
conventional gun (leaving out rocket propulsion, electromagnetics, and such).
One is the increase the temperature of the power gas, and the other is to
reduce the molecular weight. (increasing pressure, after a point, is not really
very helpful, it mainly affects the temperature.)
The way you raise the temperature and/or lower the molecular weight is by
adding in a little "bat wing" or "newts eye". Ballisticians are like rocket
propellant people, they know about all sorts of nasty stuff.
One of the well known additives is actually a component of most powers,
nitroglycerine. Just up the NG content, the velocity goes up, and the bore life
goes down.
John Salt told me that some British guy told him that the additive for the 17
pounder (and I am sure other British guns) was called "Bicarb." I don't think
that is what you take for heartburn.
A popular additive for rocket propellant (and rocket propellants have a lot in
common with high performance gunpowers.) is RDX. It works well, but actually
not quite as well as NG. It does make a less propellant less prone to
detonation than NG, which is more important in rockets. (At least, I never
heard of gun propellant detonating. I have heard of rockets detonating, lots of
times.)
Bottom line. I am sure that the 17 pounder used "hotter" propellant, bore life
be damned. And, the Germans also used hotter propellants. There are also
additives that help improve bore life a bit, lubricants as it were. But, none
that the British knew about that the U. S. didn't, and probably not the
Germans. That sort of thing is easy to "reverse engineer." And, there are not
usually availabity problems with power components.
(As there were with Tungsten, for example. And, the Germans *loved* hydrogen
peroxide, and they produced most of the world supply. The U. S. never liked
peroxide, and every now and then someone would try it again, and still didn't
like it. From very early, the U. S. liked nitric acid, and propellants based on
it, eventually culminating in N2O4, which is sort of "purified" nitric acid
with the water removed. I know of no such bias in gunpower.)
>
>> In addition to the 3 inch guns that went into the M10, there were
>> also a lot of them used as towed AT guns. Probably about as many
>> as in the TDs.
>
>I don't know how many TD battalions had them, but I've read that
>the 3-inch gun wasn't very popular on towed mounts because of
>its massive weight.
I don't know how many towed 3 inch guns there were, either. At one time, it was
the grand plan that there should be equal numbers of infantry and armored
divisions, and that the infantry divisions should have towed guns and the
armored div. SPs. Some order of battle data I have seen indicates that was
roughly achieved, but, I have no number on how many were 3inch and how many
57s.
I am currently reading "The Battle of Mortain" which is really a history of
the 30th Div. The author talks about the 3 inch a lot. but, just as all
panzers tend to be "Tigers" (not in this book, the author says that there was
only one known Tiger at Mortain, which is one more than some people think there
were.) some people think that all towed guns were either all 57s or all 3inch,
even though they are easy to tell apart.
(As I have said, Hogg in one book says that there were *no* towed U. S. AT guns
bigger than 57 mm. )
>
>They should have put the new 76mm on a towed mount to replace
>the 3-inch,
Actually, that is an idea that "missed its window." By the time that 76 mm guns
were available the experiments were with towed 90mm guns, which were heavier
yet. And, by that time, *NO* towed gun was a popular idea. Everyone wanted to
put tracks under them.
But, there were some 3inch guns that were available, and already in Europe. It
made sense to use the ones that were there, but, not to make more.
Henry Hillbrath