From: crs@beta.lanl.gov (Charlie Sorsby)
Newsgroups: rec.guns
Subject: Re: Rifled Shotgun Chokes
Date: 9 Sep 92 21:27:24 GMT
Organization: Los Alamos National Laboratory

I post the following questions, not to be argumentative, but to see
what the reasoning is.  While I'm fairly knowledgable about
shotguns, it is for bird shooting, not defense.  I'm curious about
the reasoning for a couple of the things mentioned here.

In article <1992Sep8.101237.27741@michael.apple.com> you write:
= 
= Unfortunately, reality isn't like that ...  If you have the shot
= tightly bound together with a narrow shot column (like in a .410
= bore TC) it seems to get 'lumpy'.  That is, it seems that 'chunks'
= of shot hang together a bit and go off center together...

For one thing, the .410 is purported to pattern horribly under
*best* conditions.  The long, skinny, shot column needed to squeeze
any reasonable amount of shot into that thin tube results in much
shot deformation and other nasties that contribute to anything but
uniform patterns.

= I'd EXPECT that a 12 ga. rifled shotgun (God, that's hard to 
= type with a straight face ;-)  would behave more closely in line
= with theory, but have no evidence to cite.  Perhaps someone with
= such a gun can do a pattern test on it and post the results?

Your theory (which I've deleted for brevity) sounds reasonable to
me; I, too, would like to hear results of such patterning tests.

One comment about that theory:  It makes sense with bird shot,
especially the smaller sizes, but I question it's validity with
buck shot, especially the larger sizes.  Is it 00 buck that permits
three pellets per layer in 12 bore?  With that layout, there is no
central core of shot and the pattern should be more donut like.  In
fact, I would expect that shot-charge configuration to behave that
way from a simple cylinder bore even in the absence of spin--just
a smaller donut.

= My GUESS is that the wad is going to do something odd under rotating
= conditions to interfer with the shot... but what?

I can't thing of anything.

Allow me to add a second guess.  Lead shot is deformed when a gun
is fired.  Some pellets are deformed by striking those in front
of them or by being struck by those behind.  Others are deformed by
pressure from the walls of the barrel, from the choke constriction
if any, etc.  Pellets that are not spherical do not fly true.  This
is one source of random pattern irregularities and I believe it
would be aggravated by a spinning shot charge.

= At any rate, back to the question of 'home defense' value...  At the
= ranges common in the home, I'd expect that ANY spreading of the shot,
= even if the pattern is un-even in the extream, would be welcome.
= Heck, so you have an un-even pattern, when the pattern has been opened
= up from 1 inch to 4 inches does it really matter if it is even?

But what would be the point?  There are two things to consider
here:

One is that, at typical in-house ranges, the pattern size is about
as described above.  If you can hit your assailant with a 4-inch
pattern, you can hit him with a 1-inch one and the latter has the
advantage that all the shot is concentrated in a small (frontal)
area thus behaving more like a bullet than would a 4-inch pattern.

A tight pattern would be an advantage if using bird shot.  If
using buck shot, why not just use a pistol?  (I assume, of course,
availability of both.  Clearly, if a shotgun is all you have, it
is what you would use.)  My view is that buck shot is nearly as
likely to penetrate (wall penetration is the second thing of the
two mentioned above) walls as pistol bullets so wall-penetration is
not the issue that suggests buck.  Others have, in the past, posted
here the results of experiments where even bird shot is quite able
to penetrate boards at close range.

= If it was opened to 1 foot?  2 feet?  I doubt that even rifling
= could get the pattern opened to 2 feet in a 10 foot distance ...

Here, of course, you would have some advantage vis-a-vis being able
to easily hit your assailant but, aside from buck shot, you would
have sacrificed stopping power.  With bird shot, the small pellets
are unlikely to penetrate all the way through the body of even a
quail (about as big as your fist for those unfamiliar with the
bird).  Of course penetration increases with shot size thus the use
of bigger shot for bigger birds.  But, even neglecting penetration,
the amount of energy, momentum, OGW, or any other metric of
stopping power *per pellet* is tiny.

Considering bird shot, while even a two-foot pattern (if it were
possible) at close range would be very painful if it penetrated skin,
I don't believe that it would stop a determined assailant.  It is
arguable whether it would penetrate heavy clothing.

= That would require an outward velocity of about 1/5 the forward
= velocity ... (VERY roughly) ... or about 200 fps ... What 
= acceleration outward does the (what is it, one turn in 34 inches?)
= spin induced by rifling provide?  What velocity outward would you have?

Would a rifled choke tube be able to impart a spin equal to the
pitch of the rifling?  Would it be able to grab the wad well enough
that it would follow the rifling truly or would it to some degree
slip straight through?  My guess is that it would follow the
rifling less than perfectly so that, if the pitch of the rifling
were one turn in 34 inches, the spin imparted on the shot charge
would be that of a pitch equivalent to one turn in some greater
length.  Just to further complicate the issue....

= I'd GUESS (yes, again with the guessing ;-) that you will get about
= a one half inch per foot spread or about a 5 inch pattern at 10 feet.
= I don't think that helps much over a 1 inch pattern, and I don't
= think that an un-even 5 inch pattern matters...  i.e. I think 
= the question is moot...  Put a laser sight on the gun and shoot
= any kind of barrel on it with any kind of shot, just make sure
= you hit the target in the center ...

Ah!  The last sentence says it all.  Whether you have your
full-choke tube in or your skeet tube or your rifled tube, you are
going to have to hit your target because your pattern is not going
to be anything like it is at 20-40 yards.  If the rifled tube
produces any spread at all, as Michael, I don't believe it will be
enough to make it any easier to hit your assailant but I *do*
believe that it may be enough with bird shot to decrease penetration
to some extent.  With buck, I believe it would be totally irrelevant.


-- 
Best,

Charlie "Older than dirt" Sorsby				"I'm the NRA!"
	  crs@lanl.gov