Why does speed effect pattern?

[John in WI]

I'm wondering if someone can straighten something out for me.

Today I got out to test some 28 pellet size F buckshot loads that I made. (28 pellets works out to be 7/8oz)

The Hodgdon site lists 19, 20, 21, and 22gr (International) loads for 7/8oz and the speeds going from 1250 to 1400fps.

So I tested loads at 19.5, 20.5, and 21.5gr out of a Mossy 12 with an 18.5" cylinder bore. CCI primers, WAA12 wad with ~1/4" of fiber disk in the bottom of it to bring the height of the shot up. Then roll crimped with a plastic overshot disc.

At 7 paces, the 19.5gr loads were 6" tops. Really dense, tight, and uniform. But the spread went up from there. At 21.5gr, it pretty much peppered the torso of a IPSC target. Still uniform but really spread out.

To me it doesn't make sense why it would make a difference, but from what I'm reading a lot of people report the same thing. Slower shot columns patterning tighter than faster ones at the same choke (or lack of a choke).

Any thoughts on why that happens?

[tomme boy]

Shot deforms once fired. The harder the shot, the less deformity.

[John in WI]

Hmm, I never thought of that. I cast my shot out of the very first lead I was able to scrounge. Maybe half wheel weight, half lead pipe, and some solder I had laying around. (I had no clue what I was doing--just melted some lead together). It is quite soft.

I can see where that would be a big factor for lighter shot, but this stuff is .22.
I guess that would make sense. I did a little reading a while ago about non-spherical shot that bird hunters use to open up the pattern. I saw some that were slightly flattened spheres, and even some that was cubic.

[Mk42gunner]

Shot deforms once fired. The harder the shot, the less deformity.

Plus turbulence, the faster the load the more air effects the shot, deformed or not. Shot isn't stabilized.

Compare throwing a fastball to throwing a knuckleball, a slight bit of spin really helps the fastball go where it is aimed, no spin and the knuckleball goes where it wants.

That's my theory anyway.

Robert

[x101airborne]

I have had the same results and believe me, I am just starting to understand shotgun loading at all. I was told to try nickle plated shot for my super speed loads and that really helped. Now I have good 7/8 oz loads for my wife to shoot this dove season that wont kick the heck out of her. Shot deformation at launch is hard on em and with standard lead shot it is really critical.

[John in WI]

Now that I have half a clue about lead alloys, I need to try the other alloys. The one I used here was "watered down" wheel weight. I need to cast some more balls with water dropped WW, or even my other alloy that is WW with a touch of lino and some pewter in it.

Although the first thing to try would simply be to replace the cylinder choke with something a bit tighter, and see if I can find a "sweet spot". I read in numerous places that buckshot can be funny that way--where opening up the choke can actually tighten the pattern in some cases.

I haven't played around with it much yet--this was just a prototype "milk jug blaster" load. I heard the effect was real, but was kind of surprised at how much of a difference powder charge makes. To almost double in size at only 7 paces is pretty amazing. And all of the powder charges were well within the posted recipe. I wasn't trying to "hot rod" anything.

[flounderman]

ever try to throw a ping pong ball. the ballistic coefficence is about zero. Like a knuckle ball dances. curve ball has rotation and goes straight for a ways. knuckle baqll doesn't, and dances. they have tested cube shot, odd shaped shot, swan drops and they have pretty much dismissed the theory about deformed shot. the heavier shot holds a pattern longer. I have to use buckshot for deer some places and the 000 is the way to go if you want to reach out. I don't know what you are attempting to accomplish. if you want a close range defense load, the cylinder bore is right. If you want to shoot deer at 60 yards, you need some choke. another thing is some chokes and barrels have straight rifling to stop the charge from swirling. if it does have a tendendcy to rotate, the faster you drive it the faster the rotation will be and the more dispersal due to centrifical force. I personally don't want any buckshot smaller than 00 and if I can get 000, thats my choice. But I'm hunting with it.

[Four-Sixty]

I think flounderman is on the mark when he speaks of rotation causing the shot to spin, thus opening the pattern.

I have buffered some 00 loads and seen my groups really tighten up.

[Chicken Thief]

The main culprit is speed and the transision from supersonic to subsonic.
The faster the shot goes the further from the bore the trip down through the speed of sound and the shock wave are, and the shattering effect acts on the individual pellets as opposed to the "cluster" as a whole.

[UNIQUEDOT]

If you are using a modern wad the first thing that happens when you squeeze the trigger is the leg section crushes as the crimp is being pushed open and the shot on top begins pushing itself to the bottom of the shotcup while the shot on the bottom is making it's way to the lead. The shot deforms against itself and powder charge/burn rate pressure speed and shot hardness all have an effect on how much the shot is initially deformed.

The main reason plated shot can help to improve patterns is not because it's that much harder than magnum shot, but because the plating acts as a lubricant and allows more of the shot to slip around each other with less deformation. There have been tests done using high speed photography to prove these theories. A column that starts to spin will as mentioned also wreak havoc on a shot pattern and there are choke tubes available from hastings that will grab the wad and stop it from spinning.

[Sensai]

Think about what creates the difference in velocity. It's the pressure devloped behind the wad. As the shot column starts to exit the barrel the pressure on the side of the cup is released, the cup starts to open and the shot is free to start moving sideways rather than straight down the barrel. At that point the wad still has pressure pushing it out of the barrel and into the shot column. The more pressure, the more push to disburse the shot. The higher velocity loading, the more pressure.

Just my thoughts, but it sounds good to me!

[shotman]

If you dont use shot cup wads You wont see that . remember in the time before plastic wads you could get a squrrial at 60yds .
the shot cup is like a spring the harder it is compressed the more its going to change when it leaves the barrel . If you look at the wad with the different loads you will see a low power go 40yds and a high power abut 20 yds before it splits off the trail that will change the pattern

[John in WI]

Thanks for all the information.
I guess there are a couple things to do. I was wondering about using some graphite or mica powder to lubricate the shot a little bit. I could also try a buffer. And of course, I can try the other chokes and see what that does.

I guess I was encouraged that at least the patterns were very even. 28 pellets perfectly spaced out in a circle. Now to get the same distribution, but a little less spread...

[Blair]

Very interesting.

I have been thinking that light loads at high speed would be the way to go, so that I had more ft lbs of energy..........

But if my pattern isn't holding together to strike the target.............

[fouronesix]

Well, between the time the charge is ignited and the pellets have gotten to the target down range, a whole bunch of things have been happening. Shotshell ballistics is one complicated system. The only inside info I have has to do with what the Federal shotshell ballisticians were doing in the mid 80s- mainly buffered, copper plated large magnum shot loads and of course steel shot loads. Real time pressure gauges and high speed photography of shot clouds in flight revolutionized R&D within the shotshell industry. I do know that one of the finest patterning lead shot shell loads ever developed at Federal was a 12ga 3" magnum load carrying a buffered payload of copper plated BBs at about 1200 fps. The other truly outstanding load I remember, as developed by Federal, was a 2 3/4" 12ga light magnum load of buffered, copper plated #5 lead shot. Many of the best buckshot type loads were also developed during that time with buffering being one of the key ingredients in the recipe. I don't remember any of the super high velocity lead loads patterning particularly well- in contrast to the better steel shot loads that patterned extremely well at the higher velocities.

[Blair]

Sort of like the old saying, "Slow and steady gets the job done."

Been reading a lot of the posts here as fast as my eyes can stand and am receiving quite an education quickly.

[LibertysTeeth]

doesn't the distance the wad travels that holds the shot together increase when velocity does?

[UNIQUEDOT]

doesn't the distance the wad travels that holds the shot together increase when velocity does?

The faster it's moving the quicker wind resistance should peel back the petals on the wad.

[beemer]

If you dont use shot cup wads You wont see that . remember in the time before plastic wads you could get a squrrial at 60yds .
the shot cup is like a spring the harder it is compressed the more its going to change when it leaves the barrel . If you look at the wad with the different loads you will see a low power go 40yds and a high power abut 20 yds before it splits off the trail that will change the pattern

Back in the mid 60's the only thing I had to squrriel hunt with was a 20 ga. It would take a squrriel at close to 60 yds if I used the right shells. Remington had a power piston,Winchester had a plastic wrap around the shot. Win. low power shells had more range than any thing I tried, the Remington shells were dismal. I had no clue why, just the results. I haven't thought of it for years.

I got a 22 for Christmas in 1966 and never used a shotgun for squrriels again. After reloading for 40 years just started playing with shotgun reloading. That might be something else to try.

Dave

[UNIQUEDOT]

Back in the mid 60's the only thing I had to squrriel hunt with was a 20 ga. It would take a squrriel at close to 60 yds if I used the right shells. Remington had a power piston,Winchester had a plastic wrap around the shot. Win. low power shells had more range than any thing I tried, the Remington shells were dismal. I had no clue why, just the results. I haven't thought of it for years.

I got a 22 for Christmas in 1966 and never used a shotgun for squrriels again. After reloading for 40 years just started playing with shotgun reloading. That might be something else to try.

Dave


I recall a gentleman that had a 20 ga. double Lefever that was capable of the same thing back in the 70's my uncle set up oil cans at 60 yards and shot them with Remington and Winchester shells using a 12 ga. model 12 full choke and the shot would not penetrate at that distance, but the guy with the 20 ga Lefever would shoot them and the shot would penetrate every time. They both used #6 shot and factory shells.

Winchester still used traditional wads and mylar wraps into the 90's in many factory loads and probably still do in some loads. As far as pattern disrupters go the number one factor we have to deal with in modern shotguns is the forcing cones regardless of the wad columns we choose.

[BAGTIC]

The main reason for shot dispersal is that air pressure at the front of the shot column slows it down. The tailgating or 'drafting' shot bringing up the rear collide with it from behind. Shot are round and when two round objects collide there is a camming action that tends to deflect them at angles so the column begins to spread laterally. This is the main reason short shot columns produce better patterns. 1 1/4 oz from a 10 gauge will shoot better than 1 1/4 oz from a 12 or 20 gauge because there are fewer interferring shot bringing up the rear. It is also why choked barrels improve patters. They string out the shot column so there is enough separation to delay the inevitable collisions.

Another reason is that high gas pressures at the muzzle overrun the shot column fron behind causing it to beak up like breaking the balls in a billiard game.