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 Post subject: Re: Just one load? aka: are 8.5's enough for trap
PostPosted: Fri Jan 05, 2018 5:34 pm 
Presentation Grade

Joined: Wed Mar 22, 2006 11:23 am
Posts: 829
Location: Issaquah, WA
John Henry wrote:
HTSmith wrote:
I've attributed this to the #7½ shot pellets being heavier than #8 pellets, and dropping faster due to gravity and changing the "arc" of the trajectory of the shot swam.

Thinking we better drag out the physics book on this one :)


yes, you do need to visit the physics book, because everyone who studied (and passed) physics knows that those 7.5s will drop at the same rate as 9's, 4's, 2's, etc. At a rate of 9.8 m/s/s, or meters per second squared.

It's true that gravity affects all objects the same in a vacuum. In a gaseous medium (such as air) other forces like drag come into play. For various shot sizes we might shoot, it would probably be pretty difficult to measure the difference but consider the classic brick vs. feather example. They fall at the same rate due to gravity in a vacuum - different story in air.

I suspect that a difference in hold point for different shot sizes is more likely due to the larger shot encountering more drag and slowing down faster, thus giving more time for the shot to fall before it reaches the target. However, it's been a long time since I passed my physics classes so I'm not putting any money on my thought. :wink:




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 Post subject: Re: Just one load? aka: are 8.5's enough for trap
PostPosted: Fri Jan 05, 2018 8:48 pm 
Crown Grade

Joined: Sun May 17, 2015 6:25 pm
Posts: 2161
Location: On the wrong side of the river, Austin TX
Pickman wrote:

I suspect that a difference in hold point for different shot sizes is more likely due to the larger shot encountering more drag and slowing down faster, thus giving more time for the shot to fall before it reaches the target. However, it's been a long time since I passed my physics classes so I'm not putting any money on my thought. :wink:


Small shot slows down faster than large shot. Doubling the diameter of a sphere quadruples its frontal area, which increases drag, but that is more than offset by the fact that doubling the diameter of a sphere increases its mass by eight fold.

00 buckshot fired at 1250 fps is still going 985 fps at 40 yards.

#8 shot fired at 1255 fps is only going 675 fps at 40 yards.

You can calculate the weight in grains of any lead sphere by cubing the diameter in inches, and then multiplying that answer by 1503.

For example, a .490 roundball for a .50 caliber muzzle loading rifle should weigh .49 X .49 X .49 X 1503 which comes out to 176.8 grains.

A .729 diameter lead ball weighs .729 X .729 X .729 X 1503 which comes out to 582.3 grains which happens to be 1/12 of a pound. That's why we call a shotgun with a .729 inch bore a "12 gauge".


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 Post subject: Re: Just one load? aka: are 8.5's enough for trap
PostPosted: Sat Jan 06, 2018 2:45 pm 
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Joined: Sat Oct 13, 2012 8:04 pm
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I live in a very windy part of the country . We consider a 25 mph wind as breezy. Do you think 7 1/2 shot would be better for very windy days?


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 Post subject: Re: Just one load? aka: are 8.5's enough for trap
PostPosted: Sat Jan 06, 2018 5:38 pm 
Crown Grade

Joined: Sun May 17, 2015 6:25 pm
Posts: 2161
Location: On the wrong side of the river, Austin TX
wrfish wrote:
I live in a very windy part of the country . We consider a 25 mph wind as breezy. Do you think 7 1/2 shot would be better for very windy days?


My calculations indicate that 7 1/2 shot will drift sideways about 3.2 feet at 60 yards in a 25 mph crosswind.
At 40 yards it's about 1.44 feet.
That's if Lyman's ballistic data is correct.


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