Index Home About Blog
From: John De Armond
Subject: Re: Outers electronic "Foul Out" system
Date: 31 Dec 90 05:06:14 GMT
Organization: Rapid Deployment Systems (making go-fast things and things that-go fast)

wa3wbu!john@uunet.UU.NET (John Gayman) writes:

#   I was lucky enough to have Santa bring me an Outers "Foul Out"
#eletrochemical bore cleaner for Christmas. 
[excellent description deleted]


I'd like to have a followup from you after you've had a chance to shoot
some of these guns, preferably in competition.  I'd like to know the
effects on accuracy of a very clean barrel.  I've considered the Outers
unit but am concerned that a pristine barrel might not represent the best
conditions for accuracy, especially under conditions like a silhouette
match where enough rounds are fired for the barrel to reach a sort of
a fouling equilibrium. 

I do know that if I thoroughly clean my silhouette pistols, their aim
does not stabilize for perhaps 20 to 30 rounds, which is too much for a
match. I see this effect correlated in my chronograph readings. My
current technique is to swab the barrels with Hoppes a couple of times,
followed by a couple of drying patches.  Using this technique, the
barrels reach equilibrium within the 5 practice rounds permitted.  I do
NOT try for a chemically clean barrel.  I'd like to hear about your
experiences with the product, as it appears that it will at least provide
a highly repeatable base to start from.  


From: (Bart Bobbitt)
Subject: Re: Frequency of cleaning
Organization: Hewlett-Packard Fort Collins Site

kunz peter ( wrote:

: what about th ebreak in aftre cleaning? i seem to need at least 5 rounds
: ot get back the sam esettings i had before i cleaned the gun, and thne
: it stays consistant. is it just me?

If any barrel needs several rounds through it before shot impact gets to
point of aim, that barrel's bore is scraping jacket material off those
`break-in' bullets.  Once the bore's rough spots are full of jacket
material, very little more bullet jacket material is scraped off.  Then
the bullets shoot closer to point of aim.

This is very typical of factory barrels.  A lot of aftermarket barrels
are the same way.  Only top-quality target barrels have their bores made
uniform and smooth enough to shoot to point of aim when clean for the
first shot.  Except the slightly lower velocity causing the first 1 or 2
shots to strike low due to the cold barrel not warming the powder up to
what it will be later sometimes happens.  Or the added fouling for the
second or third shot will cause the same effect.  But these two causes
of low-first-couple-of-shots is only noticeable at ranges of 300 yards
and greater; at 300 hardly at all, at 1000 perhaps one MOA low.  The
first shot's velocity is only about 20 - 40 fps below average velocity.


From: (Bart Bobbitt)
Subject: Re: Frequency of cleaning
Organization: Hewlett-Packard Fort Collins Site

Lloyd D Reid ( wrote:

: It's somewhat counterintuitive that increased bore friction increases
: muzzle velocity, but that's what seems to happen most of the time.

In tests using the same .308 Win. case for each shot, chambered
15 seconds before shooting, and shooting that case at exact 1.5 minute
intervals, muzzle velocity increases about 1.5 fps per shot after the
first two shots foul (and warm up to some degree) the barrel.  This may
not be very obvious when velocity spread for 10 shots is 50 or more fps.
When velocity spread is below 25 fps, it starts to become apparent.  A
regression analysis is done on the individual velocities in the order
fired to get the average velocity increase from one shot to the next.

Which easily explains why many long range target shooters need to come
down a quarter MOA a time or two during a 25-shot session.


From: (Bart Bobbit)
Subject: Re: vertical shot string
Organization: Hewlett-Packard Fort Collins Site

One thing I've noticed in chronographing loads is the first shot from a
clean barrel is typically at a lower velocity than the second one.  And the
third will be higher than the second one.  At about the fourth or fifth shot,
velocity has stablized and shots tend to stay at the same elevation.  This
has been seen in tests and normal shooting conditions at all ranges through
1000 yards.  And it doesn't make any difference whether the barrel is hot
or cold when starting the series of shots.  Once in a while, a barrel won't
exhibit this situation, but more often than not, it's very normal.

The reason seems to be that as fouling builds up in the bore, that increased
resistance causes higher pressure; hence higher velocity for each succeding
shot.  After the fouling/resistance has `normalized,' velocity stablizes for
the most part.  Velocity in my .308 Win. rifles for the first shot is often
30 to 50 fps lower than normal for the first shot from a clean barrel.  And
that first shot is low on the target, too, but I know how low it will be and
make sight adjustments off of the first shot accordingly.


From: (Bart Bobbitt)
Subject: Re: Spinning bullets and asymmetry - (Was: Re: Long range rifle)
Organization: Hewlett-Packard Fort Collins Site

J. Spencer ( wrote:

: An interesting point. Last weekend, I was debating with my twin why the
: first round from a clean barrel deviates from the point of impact of
: subsequent rounds (yes, that old chestnut). He came up with all kind of
: theories, most of which have been covered here. But he did raise one
: pertinant question. Consider the following.

: My rifle (a Ruger M77 in 243) was zeroed to fire a 100 grain bullet at
: 100 yards. The first round from a clean barrel always goes 2" low and
: left, at 7 o'clock, say. On Sunday, the first round was a 70 grain
: bullet. As you might expect, it went high. In fact, it went two inches
: high at around 11 o'clock (i.e. up 4 inches in total). Now my twin's
: observation was that, OK the bullet went high as might be expected
: since it is lighter, but *it still went the same amount to the left*.

: He suggested that this may be one effect of using a rifled barrel, that
: is, that a smooth bore gun would not shoot off to one side like this
: from a clean barrel: it might shoot high or low, but the lateral
: deviation must be some effect of the rifling.  Offhand, I can't recall
: whether the rifling in my rifle is clockwise or anti-clockwise, but
: what's the net.wisdom?

If the first shot is to either side, that's typically caused by the
shooter not getting the shot off correctly.  A usual cause is the trigger
isn't pulled straight back.  Another cause is the shooter flinches a tad
on the first shot; typically in the same direction each time.  Rifling
direction has nothing to do with it.

The reason the first shot goes low is because the velocity of the first
bullet from a clean barrel is lower; often by as much as 60 to 100 fps.
But that's only going to cause about a 0.2-in. vertical difference at
100 yards with most cartridges.  At long range, such as 1000 yards, the
first shot often is 20 to 30 inches lower than the second one.  After
the barrel has fouled, resistance to the remaining bullets is greater.
This increases both pressure and velocty.


From: (Bart Bobbitt)
Subject: Re: Spinning bullets and asymmetry - (Was: Re: Long range rifle)
Organization: Hewlett-Packard Fort Collins Site

J. Spencer ( wrote about my comments (: #):

: #The reason the first shot goes low is because the velocity of the first
: #bullet from a clean barrel is lower; often by as much as 60 to 100 fps.

: Is that because trace oils lubricate the bullet, or because the carbon
: and copper deposits create friction (or both)?

I think both have an effect.  And the bore finish in microinches can also
have an effect.  Factory barrels are notorious for being rough.  And their
rough spots can be more in one groove or on one land more than the others.
This is often the cause of the first shot going in the same direction from
group center than the rest.  As long as the shooter knows his barrel's
first-shot characteristics, that's fine.

Even with a match grade barrel lapped to a 5 to 10 microinch finish that's
been shot 10 to 20 shots, then allowed to cool to ambient temperature, and
not cleaned, will have its first shot in a later fired string go a bit low.

I've cleaned some match barrels immediately after firing 20 to 30 shots,
then `de-lubed/greased' the bore with lighter fluid (even tape head cleaner).
That, I think, removed any and all trace residue of bore cleaner; the metal
surface was free of any cleaner or lubricant of any kind.  The first shot
from such a squeeky-clean bore still goes low; like about 1 to 1.5 MOA at
1000 yards and about .25 to .50 MOA low at 600 yards.  But in other match
barrels, a squeaky clean bore will put the first shot where the rest of the
shots go.


Index Home About Blog