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Author Topic: What causes "donut holing" in a shot pattern?  (Read 1582 times)

Offline Loyalist Dave

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Re: What causes "donut holing" in a shot pattern?
« Reply #15 on: June 28, 2012, 09:29:35 AM »
I would REALLY like to see those photos, as I was of the opinion that the lack of mass of a wad, either felt, or paper, or modern plastic coupled with the surface area of the wad compared to the spheres of the individual shot pellets, would cause the wad to decelerate from air friction when the gas column was not contained by the barrel, (even with some shot stuck into the top surface of the wadding material), and the deceleration would be so fast on the wad as to prevent the wad from passing through the shot column that has exited the smooth bore barrel.  One reason for this was the observation that at very close range, when patterning or firing at a static target, the wad does not fly straight, and in fact often hits the target outside of shot pattern, due to air friction deflecting its path.

The other reason for this hypothesis was in reading Forsythe's The Sporting Rifle and Its Projectiles , he covers why the round ball from a smooth barrel deflects sooner in flight than when fired from a rifle barrel that imparts a controlled torque, and the same forces would apply to a shot column fired on the horizontal..., in fact because the shot column is composed of multiple pieces of shot, the column will tend to react to the tendency to be "unbalanced" more than a solid ball, and this unbalanced state when the shot is fired, imparts torque or rotational movement to the shot as it approaches the muzzle, thus blowing the pattern.  

The reduction of the torque is accomplished, or less amplified, I thought by reducing the powder to reduce the velocity, or by increasing the amount of shot which increased the mass, and reduced the velocity.  The torque or tendency to rotate, was further reduced then and today, by the use of "gooved" or "straight rifling" to thus correct or eliminate the torque, and the modern use of choke tubes that employ grooves to obtain a tighter pattern over identical choke tubes that do not, further point to torque and not wads blowing or donutting patterns..., or so I had thought... for folks with donut pattern problems, when using the same load but switching to a same gauged smoothbore that has a gooved barrel report elimination of the pattern problem.  Also when using the same ammuntion but adding a grooved choke tube in a modern shotgun, eliminate the blown patterns.  IF it was the wads and not torque, the wads should still blow through..., gooved or not grooved, torque reduced or not....

..., but if there is photographic evidence showing the blow through of wads, then perhaps torque is a very minor factor, with the wads are the real culprit, and the modern choke tubes with the grooves cause the wads to not pass through the shot, which is really how they help?  But what about grooved barrels which impart less friction to the surface area (in theory) of the wads than a plain barrel..., why do they stop donut patterns...?  

How does reducing the velocity suddenly cause the wad to sufficiently slow down to not blow through the pattern?  I mean if you launch the shot and wad at 1100 fps and that causes the wad to pass through the shot pattern, then how does reducing the MV to 800 fps not cause the wad to pass through the shot pattern?    The wad must pass through the column very soon after exit from the barrel, otherwise the pattern would be so wide that the amount of shot impacted by the wad would be minimal.  Deceleration ratios should be a constant for shot and wad at either speed, 1100 fps or 800 fps... ??

Or wait, is the air compressed quicker, thus increasing the friction at a higher MV?  

AAAAAAAGGGGH!  :cry:   I should've paid more attention in physics class.   :cry:

LD
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Offline Stormrider51

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Re: What causes "donut holing" in a shot pattern?
« Reply #16 on: June 28, 2012, 10:42:37 AM »
Dave,
You may be correct about rotational torque.  It certainly makes more sense than the idea that the wad is blowing through the pattern.  The light weight and large frontal area of the wad compared to the shot column would seem to prevent that from happening.  The photos I saw only revealed the donut hole in the shot pattern, not the wad traveling through the pattern.  And yet several others on this forum say they corrected the problem by eliminating the cushion wad.  It has me scratchin' my head.

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Offline Captchee

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Re: What causes "donut holing" in a shot pattern?
« Reply #17 on: June 28, 2012, 12:02:36 PM »
ill see if i can find the photos and post them .
 in the main time here are 3  photos to consider .
 Note that one of these photos was taken at the muzzle .
 The other to are an un disclosed distance from the muzzle . These photos are also from a choked bore having BP paper cartridges fired through it   .
 IMO we would see an even greater  spread of the shot  as it leaves the muzzle  of a cylinder bore .
also note that at the point these photos were taken the wad was beginning to move into the shot as noted by  the spread of the shot as well as some  of the shot itself being  back along the outer edge of the  wad ..
again i will have to do some digging but i recall having  other Greener photos that show even more dramatic happenings where the wad is well through the shot column . One is even of a shot cup  rotating and throwing the shot  as it falls away.  

 note the effect the wad  is having on spreading the  shot column. While the over the powder cards are lagging and falling away . The wad is still very much in contact with the shot .
 Here is what im thinking actually happens . I could be wrong of course .
 What I think happens is that the  shot column creates a venture effect  holding the wad  for a longer time , up against the shot . As the shot starts to spread  the wad is carried even more . At least until such time as  its weight and resistance  pulls it way. Until that happens though  it appears the wad does effect the shot  by pushing it wider  as the leading edge of the column encounters resistance  and spreads



Offline Stormrider51

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Re: What causes "donut holing" in a shot pattern?
« Reply #18 on: June 29, 2012, 01:03:30 AM »
Okay, take a look at the photos.  I see some shot pellets breaking away upwards and a greater number falling away below.  The main pellet column is still heading downrange well ahead of the cushion wad.  At what point does the cushion wad suddenly become capable of passing through the shot column and creating a hole in it?  Captchee, I mean no offense and I truly appreciate you providing these photos and any others that might shed some light on this.  The fact that this phenomenon occurs seems to be established beyond doubt, at least in certain conditions.  I'm just not convinced as to the "why".  I think I see some time spent patterning birdshot on paper using different wad combos in my future.  And this leads to another thought.  Does it happen with larger (ie: buck) shot?
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Offline Captchee

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Re: What causes "donut holing" in a shot pattern?
« Reply #19 on: June 29, 2012, 10:03:39 AM »
what your seeing the  shot column beginning to spread . it will continue to open up as it goes down range . the main  part of the column is whats just in front of the wad .
 its IMO also note worthy to mention that  open holes can also be contributed to whats called shot clumping . IE because of the  type of shot , make up of the load , type of wads , cards...  a given type of shot can  clump up  into tighter sections . McPherson mentions this in his writings .
 but here is the thing . we can talk about who says what all day .  it doesnt change the fact that the information has to relate  to the shooter specifically . going out and shooting a couple patterns isn’t going to tell you much . you need to shoot several patterns and then compare  those  as an average .
 F your consistently seeing the holes  in the pattern , in relatively the same locations . Then  start  working on your loading . Try dropping the wad and see what happens . From my experience  dropping the wad or going to a softer wad often  results in the holes in the pattern  going away . Reducing the powder charge to shot ratio  will tighten the pattern. More times then not , adding more powder to shot , opens the pattern up “cylinder bore application “
 With my 12 gage guns, both muzzleloader Cylinder bores  and BP paper cartridge  ,choked bore . I can tell you that I don’t shoot more the 70 grains of 2F  behind 1 ¾ oz of #7, graphite   and they pattern wonderfully out to 30 yards  .

at what time does the  wad pass through ?
well  as i said greener  showed some test that the wad actualy was  more through the column / IMO this would produce a donut  type of  pattern . if however your just getting holes in the pattern then  the case could be made that the wad is disrupting  the patern enough  to cause the holes . again if you drop the wad and find that those holes  go away OR that the center of your pattern is now more full . what does that lead you to believe?

Offline pathfinder

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Re: What causes "donut holing" in a shot pattern?
« Reply #20 on: June 29, 2012, 02:39:41 PM »
So far in my 10 bore Bess; 65grs 2f,over powder card,5/16 felt wad,over shot card,1-1/2 measure of powder diveded into 3 section's,shot o/scard,shot,o/s card,shot o/s card.
Seem's I'm missing A LOT closer than before!
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Offline Captchee

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Re: What causes "donut holing" in a shot pattern?
« Reply #21 on: June 29, 2012, 05:44:29 PM »
i have heard that some folks have luck with dividing up the shot column . myself i have not gotten good result to often by doing that

Offline Andy54Hawken

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Re: What causes "donut holing" in a shot pattern?
« Reply #22 on: July 01, 2012, 01:38:06 PM »
I've found some things to try out after reading ths thread.
Thanks for sharing,
Andy
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Offline pathfinder

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Re: What causes "donut holing" in a shot pattern?
« Reply #23 on: July 01, 2012, 02:45:17 PM »
This is the cool thing about muzzleloading, Ya ALWAY'S have sumthin ta fool with! Most of us hardcore,greybeard muzzleloaders are tinkerer's of one sort or another,alway's messing with SOMETHING,ALWAY'S! And trade gun's give us another reason to head to the range,IF we can get out of our "Tinker Room"(grandkid's call it that, Dzia-Dunio is alway's tinkering with something!)
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Offline Andy54Hawken

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Re: What causes "donut holing" in a shot pattern?
« Reply #24 on: July 01, 2012, 03:03:03 PM »
Always something to fool with, truer words were never spoken.
Yesterday I went out with my northwest gun. Did some shooting with round ball and also with shot.
Did ok with round ball out to 50 yards.
Need to work on a better load or just get more time on the gun to hit more with shot....
Some good ideas on this thread to try out.
Andy
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Offline Stormrider51

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Re: What causes "donut holing" in a shot pattern?
« Reply #25 on: July 01, 2012, 08:29:44 PM »
Quote from: "Andy54Hawken"
Always something to fool with, truer words were never spoken.
Yesterday I went out with my northwest gun. Did some shooting with round ball and also with shot.
Did ok with round ball out to 50 yards.
Need to work on a better load or just get more time on the gun to hit more with shot....
Some good ideas on this thread to try out.
Andy

Glad you found it useful.  I plan to do some patterning using different wad combos and see what happens.  I'll report it here.  One of the great things about the internet is that there is a tremendous amount of info available on just about any subject.  Like Path said, there's a bunch of old greybeards in the association with many years of experience and a willingness to share it.  Another great thing is that I haven't dealt with anyone in the TMA who I wouldn't want to share a hunting camp with.  I can't say that about all the muzzleloading forums.  You might consider joining.  It's only $16 and you are helping to keep the association, and the forum, going.

Storm
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Offline sse

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Re: What causes "donut holing" in a shot pattern?
« Reply #26 on: July 02, 2012, 11:12:30 AM »
Quote
Another great thing is that I haven't dealt with anyone in the TMA who I wouldn't want to share a hunting camp with.

 :bl th up
Regards, sse

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Offline Loyalist Dave

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Re: What causes "donut holing" in a shot pattern?
« Reply #27 on: July 06, 2012, 08:09:49 AM »
Thanks for the photos.  I'm gonna need to find a guy at the ATF lab with a high speed camera and convince him it's important to test this and get a photo of the wad actually passing through the shot.  (The lab is right down the street from me).  

GAH!     :rt th

LD
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Offline Loyalist Dave

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Re: What causes "donut holing" in a shot pattern?
« Reply #28 on: July 06, 2012, 08:16:35 AM »
OOOOH wait...,

I wonder from the first photo if it in some or all cases might be the opposite of "blowing through"..., say  upon detonation, the inertia needs to be overcome, but in that process depending on the wad material - say a lubed felt wad, a significant portion of the shot gets imbedded in the surface of the wad, perhaps a layer into the wad and a layer of shot into that first layer... just enough so that upon exit from the muzzle..., those two layers of shot are retarded/slowed down just a tad, and those pellets then drop lower in the pattern due to lower MV than the rest of the pattern, and thus causes the donut???

LD
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Offline pathfinder

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Re: What causes "donut holing" in a shot pattern?
« Reply #29 on: July 06, 2012, 09:34:03 AM »
LD,do you have a part in "The Big Bang Theory"? You sound like Sheldon!  What you stated is exactly what I have thought was happening,so I started to put a over powder card over the cusion wad. It seemed to help. Still suck at bird's,but I feel better anyway!
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