15mm rifles

A thread of 2 messages, 19 November 1993 to 20 November 1993, in the order they were sent.

#6352 15mm rifles

Peter H. Brenton · 19 November 1993

[email removed] (Mark Urbin) says;

>  I noticed someone
>was designing a *large* rifle.  In the 15mm range.

for those of us not particularly familiar with real-life weapon
diameters (or at least not in millimeters) could you put this into
context please?

I *thought* that a 30-06 rifle had a round 6/10ths of an inch in
diameter (this doesn't sound right to me).  That would make it
(using my thumbnail approximation of 25 mm to an inch) about
15mm diameter.  This can't be right if your talking about 15mm
being a *large* rifle, I assume your talking about an elephant rifle,
not a deer rifle.  Could someone please correct me?

It would also be helpful to me if someone could post a list of standard 'real'
weapon calibers and show their diameter in mm (ie. .357 Magnum=XXmm pistol).

btw, if anyone is looking for a source of less than usual weapons for a
traveller campaign, I've always used the weapons from Traveller 2300.  There
are several combined weapons (ie gauss rifle/grenade launcher), they can be
easily translated in game terms, and they have great pictures for every
weapon.  Keep in mind though that they are at tech level 11 or 12.

Of course, I was always a fan of the very thin very high velocity round
which should have a better penetration than any large (non-explosive) round
in any case.  It will also, of course, do less damage (which is why you fire
a three round burst, or full auto)

I also wonder about how ff&s handles recoil for these *large* rifles.

Pete

"The opinions expressed certainly have nothing whatever to do with
the University of Chicago or the Department of Biochemistry (I just
work there and use their toys)."

Peter Brenton					   [phone removed]
Biochemistry & Molecular Biology	[email removed]
The University of Chicago

#6354 Re: 15mm rifles

Mark F. Cook · 20 November 1993 · reply to #6352

In Message-Number: 6352 Peter H. Brenton [email removed] writes:

> [email removed] (Mark Urbin) says;
>
> >  I noticed someone
> >was designing a *large* rifle.  In the 15mm range.
>
> for those of us not particularly familiar with real-life weapon
> diameters (or at least not in millimeters) could you put this into
> context please?

OK, the largest caliber sniper rifles currently in use today (the RAI
Model 500 and the Barrett Light .50) fire the .50 Browning round (the
same shell used in a Browning .50 caliber heavy machinegun of WWII
fame).  That's a 1/2 inch diameter slug, which works out to 12.7mm.

The largest caliber American centerfire cartridge ever produced (and
now obsolete) is (was) the 70-150 Winchester.  Developed as a novelty
in 1888, it was based on a brass 12-gauge shotgun shell, which was
shortened and necked slightly.  A specially manufactured Winchester
1887 shotgun (with a rifled barreled) was created to fire it.  Neither
the weapon or the shell were ever produced in commercial quantities.
It would have been considered a 17.9mm rifle.  Ouch.

The largest sporting round currently in production is a proprietary
(wildcat) cartridge called the 700 Nitro Express.  It includes a slug
that is .7 inches in diameter (making it a 17.78mm weapon) and, as
the name implies, being shot with it is like being hit by a train.
There's not much recognizeable left afterwards.  With a muzzle velocity
of 2000 fps and a muzzle energy of 8900 fpe, it is the most powerful
sporting cartridge in the world.

> I *thought* that a 30-06 rifle had a round 6/10ths of an inch in
> diameter (this doesn't sound right to me).

You're right, it *isn't* right. :^)  The 30-06 U.S. Springfield (as
the round is formally described) uses a slug .308 inches in diameter,
which would make it a 7.8mm rifle in MT terms.

>                                             That would make it
> (using my thumbnail approximation of 25 mm to an inch) about
> 15mm diameter.  This can't be right if your talking about 15mm
> being a *large* rifle, I assume your talking about an elephant
> rifle, not a deer rifle.  Could someone please correct me?

Done.  See above. :^)

> It would also be helpful to me if someone could post a list of
> standard 'real' weapon calibers and show their diameter in mm
> (ie. .357 Magnum=XXmm pistol).

Sure.  Here are some of the more common handgun calibers (for weapons
not already described in millimeters):
        .22*      = 0.223mm (*=short, long & long-rifle)
        .25 ACP   = 6.38mm
        .32 ACP   = 7.85mm
        .380 ACP  = 9.04mm
        .38 Spec. = 9.07mm
        .357 Mag. = 9.07mm
        .40 S&W   = 10.16mm
        .41 Mag.  = 10.41mm
        .44 Mag.  = 10.9mm
        .45 ACP   = 11.48mm
 ...and for centerfire rifle calibers:
        .243 Winchester      = 6.17mm
        .270 Winchester      = 7.04mm
        .30-30 Winchester    = 7.62mm
        .308 Winchester      = 7.62mm
        .458 Winchester Mag. = 11.63mm
        .460 Weatherby Mag.  = 11.63mm
        12-gauge shotgun     = 18.5mm (bore diameter, open choke)

Bare in mind that while one caliber may be equal to or larger than another,
it is by no means safe to assume that size equals power.  The .38 Special
and .357 Magnum handgun rounds use slug with identical diameters, but
the .357 is much more powerful.

In addition to the above rounds, we've already got handgun rounds in
9mm and 10mm, plus rifle rounds in 5.56mm (NATO), 7mm, and 7.62mm (also
NATO).  There are others, but they tend to run towards the more exotic.

> Of course, I was always a fan of the very thin very high velocity round
> which should have a better penetration than any large (non-explosive) round
> in any case.  It will also, of course, do less damage (which is why you fire
> a three round burst, or full auto)

This may be true for infantry weapons, but for tanks, it's a different
story entirely.  The most effective anti-armor shell currently in use
by the U.S. Army's M1A2 MBT (main battle tank) is the 120mm APFSDS
(Armor-piercing, Fin-stabilized, Discarding-sabot) round.  It throws
a 10 lb. tungsten carbide 'flechette' at almost 5,500 fps.  When it
hits enemy armor (BTW, it can penetrate up to 15" of steel), it drives
throw the plating, disintegrating as it goes.  By the time penetration
is complete, roughly 100 fragments (from the dart and enemy tank hull)
over 1 oz. each, plus over 600 smaller fragments, are moving inside
the target at velocities still in excess of 2,800 fps.  What happens
to the enemy tank crew at that point is best left to the imagination
(although I do have a document that details the results, if anyone
is morbid enough to care.)

Later,

        Mark F. Cook

USMail: Hewlett-Packard
        Workstation Technology Division - Corvallis (Tech. Marketing)
        [address removed]

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