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 Post subject: Trapshooting POI
PostPosted: Wed Oct 21, 2020 3:30 pm 
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Location: 35 miles from Normal, Illinois (as close to normal as I'll ever be)
I didn't want to hi-jack the other thread, so....

I’m going to take a stab at explaining the 16 yard v 27 yard POI difference, as I see it. While individual shooting styles can have a great influence on results, here is how the numbers crunch for me.

First some assumptions
1. We are shooting 1200 fps #7.5 shot for both
2. We will use a post 3 straight away target as an example.
3. Our trigger timing is consistent from both 16 and 27 yards. So, the target will be at the same point in its flight when we pull the trigger.
4. Using info from Remington, we will assume the target is 20 yds out of the house when we pull the trigger.
a. Shooting from 16 yds, the target will be 36 yds from the gun
i. 3.4 in drop .132 sec tof
b. Shooting from 27 yds, the target will be 47 yds from the gun
i. 7.0 in drop .191 sec tof
c. Drop is calculated from line of bore
5. We will assume a target speed of 60 ft/sec, which is pretty close to actual
6. Using info from Remington, we will assume the target height increases about 4 inches for each yard of target flight, at the range we are shooting the target

OK, here we go:

From 16 yds, we call pull, the target leaves the house and we pull the trigger when it is 36 yds from the GUN. It takes the shot charge .132 seconds to arrive. During that time, the target travels an additional 2.64 yds, and rises about 10.5 inches. So, if we point directly at the target when we pull the trigger, our POI must compensate for 3.4 in shot drop plus 10.5 in target rise, or be 13.9 inches high.

From 27 yds, we call pull, the target leaves the house and we pull the trigger when it is 47 yds from the GUN. It takes the shot charge .191 seconds to arrive. During that time, the target travels an additional 3 yds, and rises about 12 inches. So, if we point directly at the target when we pull the trigger, our POI must compensate for 7.0 in shot drop plus 12 in target rise, or be 19 inches high.

Note: If you have already set your POI correctly for 16 yds, you would only need to compensate for the additional 3.6 inches of shot drop and 1.5 inches of target rise at 27 yds, or an additional 5.1 inches raise in POI.



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 Post subject: Re: Trapshooting POI
PostPosted: Thu Oct 22, 2020 7:58 am 
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Joined: Mon Jun 25, 2018 8:48 pm
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Thanks for posting that info!


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 Post subject: Re: Trapshooting POI
PostPosted: Thu Oct 22, 2020 5:35 pm 
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Joined: Wed Mar 04, 2015 2:32 pm
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Where does the shot drop number come from? Is that number for shot fired horizontally or fired at the upward travel of the target?


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 Post subject: Re: Trapshooting POI
PostPosted: Thu Oct 22, 2020 7:46 pm 
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Joined: Fri Jun 19, 2020 9:21 pm
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We shot from the 24 yard line the other day and I wasn’t very successful. I’d shot from 21 and had done fairly well so I’m not sure why 9 more feet made it so much harder however I had a hard time with lead on the hard rights from station 5. I’m wondering how much the lead changes out there.


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 Post subject: Re: Trapshooting POI
PostPosted: Fri Oct 23, 2020 4:59 pm 
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Location: brisbane,australia
dont think about lead,watch the target shoot the target simple


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 Post subject: Re: Trapshooting POI
PostPosted: Fri Oct 23, 2020 8:12 pm 
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Yes the shot drop is relative to line of bore, as if fired horizontally.

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 Post subject: Re: Trapshooting POI
PostPosted: Sun Oct 25, 2020 6:18 pm 
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That is what I thought. The math is incorrect.

When launching a projectile horizontally there is no positive "Y" component working against gravity. Therefore the shot immediately begins to drop due to the negitive "Y" value of gravity. I would not argue the Reminton number.

When shot at a 21 degree up angle, the angle the target is traveling off the trap (or whatever rising angle it is), there is a significant positive "Y" component working against the negitive "y" component of gravity. At 36 & 47 yards from the gun the shot stream is still going up, not down.


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 Post subject: Re: Trapshooting POI
PostPosted: Mon Oct 26, 2020 11:14 am 
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"At 36 & 47 yards from the gun the shot stream is still going up, not down. "

It's going up but it is going up at a decreasing rate. As such, it will hit below the bore line extended.


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 Post subject: Re: Trapshooting POI
PostPosted: Mon Oct 26, 2020 1:46 pm 
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Not sure what you are trying to say, but regardless of the angle any projectile is launched, from the instant it clears the muzzle it is dropping, relative to the line of the bore. The amount of drop at a given range is a function of time of flight. POI, relative to line of sight/POA, must compensate for that.

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 Post subject: Re: Trapshooting POI
PostPosted: Mon Nov 02, 2020 12:22 pm 
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Tal, very good post - thank you.

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 Post subject: Re: Trapshooting POI
PostPosted: Sun Nov 22, 2020 5:59 pm 
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All this FPS, POI, shot drop and Y value of gravity stuff just make my head hurt. When pointing the busy end of the shotgun at the moving very fast orange thing where do you want the stacked beads to be pointing in relation to the orange thing when the gun goes bang?


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 Post subject: Re: Trapshooting POI
PostPosted: Mon Nov 23, 2020 1:59 pm 
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Stacked beads are useless unless you have an adjustable comb and rib. The chances that the factory put the mid bead where you can stack them and get a correct-for-you POI is about 5%.


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 Post subject: Re: Trapshooting POI
PostPosted: Mon Nov 23, 2020 2:35 pm 
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So, is a correct statement that to maintain your sight picture(s) you would need to raise your pattern up approximately 20%?

Then, by using Rollin Oswalds's comb equation, for someone shooting within the parameters set in the first post AND shooting a 32 inch barrel, one would need to raise their comb OR lower their rib by ~3/32 of an inch to maintain bead/target relationship?


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 Post subject: Re: Trapshooting POI
PostPosted: Mon Nov 23, 2020 6:22 pm 
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Joined: Fri May 09, 2008 9:17 pm
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Location: Kansas, Land of Oz
Tal/IL wrote:
Not sure what you are trying to say, but regardless of the angle any projectile is launched, from the instant it clears the muzzle it is dropping, relative to the line of the bore. The amount of drop at a given range is a function of time of flight. POI, relative to line of sight/POA, must compensate for that.

Actually the amount of drop from line of bore will change with the angle of the bore.
Picture this: if the bore is held straight up/perfectly vertical, the shot charge will remain on the line of bore until it hits the ground. Same if the bore is pointing straight down at the time the shot is fired. Maximum drop will occur with the bore held perfectly horizontal. As the bore is angled ever-more "up", the drop will decrease, until the bore is vertical, at which point there will be zero "drop".
This decrease in drop will not affect our POI until the bore is being held at more than a 45 degree angle. Since we don't shoot trap like that, we can effectively ignore it....but it DOES happen.


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 Post subject: Re: Trapshooting POI
PostPosted: Wed Nov 25, 2020 9:12 am 
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Make it easy......If your shooting well from 16 yards and move back to the 25 or more yards. Add an 1/8th inch thick washer and try it. The washer will compensate for the gravity shot drop using a 3 dram load, but has no effect on your handling and timing. You will have less required gun movement for longer yardage, from to your starting point to the moving target. Longer yardage can change your move control and trigger timing.

If not already, put a tighter choke in as well.

Maltz

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 Post subject: Re: Trapshooting POI
PostPosted: Mon Nov 30, 2020 12:35 pm 
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Jim, the beads allow one to put his head the same on the stock every time, be they stacked or with a gap between them. That way the gun will shoot to the same POI, where ever that is. So, IMHO they are not useless and do serve a purpose. I think you were being a bit hard on Mr D, but that too is just MHO. Have a good day.

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 Post subject: Re: Trapshooting POI
PostPosted: Fri Jan 01, 2021 10:11 am 
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A good friend took a shooting lesson from Phil Kiner years back and the first thing Phil did was add spacers to the comb when shooting from the back fence for just about everyone in the clinic.


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 Post subject: Re: Trapshooting POI
PostPosted: Sat Jan 02, 2021 2:33 pm 
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Location: Indiana
Gee thanks! One more thing to think about!

Interesting analysis though!




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