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First shot on a spinner- top, bottom, or no difference? Thinking through the physics I am inclined to say Top.

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top first with all types of guns.  I own an MGM spinner and have practiced all of this out on the time clock. Figured out the patterns that work with the least amount of down time waiting for the plates to be in a shooting position.

 

with shotgun birdshot: 2 hits top, 3 bottom, its over.

with rifle: 3 hits top, 3 hits bottom, its over.

with pistol: 2 hits top, 3-4 hits bottom, 1 hit top, clean up back side of bottom plate, its over.

with PCC: 4 hits top, 4 hits bottom, its over.

 

Of course that pattern is what I have figured out and works for me with my gear.

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nguy, you doing any double taps, or are all those alternating shots?

 

i've thought top first too, hit the smaller target while it's stationary.

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double and triple taps depending on gun type. No single shots unless it is the back side of a plate driving it over.

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That is definitely different from the way I see it shot and have tried to shoot it. Which is alternating top and bottom timed so the bullet hits when texas plate has started its back swing. 

 

 

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Ammo type seems to make a difference also. FMJ and lead seemed to transfer more energy than JHP type of bullets for pistol or pcc. Seen 1 shot of #6 shells spin it over if it’s allowed, as well as choke choice. 

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What I was really hoping to get at with this topic was the science and practicality of starting with top versus bottom. That is, the top is a smaller i.e. lighter target and is thus affected more by the round impact than the larger lower plate. Except that the heavier lower target is attached on the end of a "lever" to the lighter upper target so how does that affect the efficacy of shooting the top first? If I owned a spinner I would set a test up to measure the angle of deflection following impact in dead center of each plate. Maybe they are the same, since the two plates are joined, I am not schooled on physics enough to know. If they are the same then starting on the bottom makes more sense since it is larger target. There are other factors as well.

 

With a shotgun, for example, it would seem to me that starting on the lower plate is clearly advantageous, since there is more surface area meaning more of the pattern will impact that plate as opposed to the top.

 

To be clear, my spinner performance is hardly the area I most need to focus on, I just thought it might be interesting to dissect here.

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7 hours ago, Blockader said:

What I was really hoping to get at with this topic was the science and practicality of starting with top versus bottom. That is, the top is a smaller i.e. lighter target and is thus affected more by the round impact than the larger lower plate. Except that the heavier lower target is attached on the end of a "lever" to the lighter upper target so how does that affect the efficacy of shooting the top first? If I owned a spinner I would set a test up to measure the angle of deflection following impact in dead center of each plate. Maybe they are the same, since the two plates are joined, I am not schooled on physics enough to know. If they are the same then starting on the bottom makes more sense since it is larger target. There are other factors as well.

 

With a shotgun, for example, it would seem to me that starting on the lower plate is clearly advantageous, since there is more surface area meaning more of the pattern will impact that plate as opposed to the top.

 

To be clear, my spinner performance is hardly the area I most need to focus on, I just thought it might be interesting to dissect here.

I usually start on top smaller plate to get some momentum going, then hammer the bottom larger plate. Sometimes I’ll have to shoot smaller plate on bottom if it’s not quite enough to get it over. 

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10 hours ago, orangeman711 said:

nguySBR1

What distances are you talking?

 

15-25 yards for pistol, PCC, and Shotgun

100 yards for rifle. Rifle being an AR15 in 556nato.  Heavier calibers swing it faster.

 

From my timed testing, I found shooting the top then the bottom was always faster.  BUT.. I am not waiting for the plates to get to vertical before shooting em.  If you wait for a vertical plate to engage, then your shots will be behind vertical. Timing to drive the plates is how you push em over faster.

 

Example 1: Starting top plate with Shotgun, 2 fast hits, then 3 hits to the bottom. I start shooting the bottom plate as soon as it is presented enough to shoot at. I don't wait for it to get back to vertical before shooting at it.  Gun and ammo details also matter. 18" barrel with improved cylinder choke, federal 12G #8 1.1/8 at 1145FPS. Most matches I go to have a #6 and 1300FPS load limit and a massive penalty for knocking the spinner down with too hot ammo. Because of those limits, I don't waste time on special ammo to do the work.

 

Example 2: Starting top plate with PCC, 4 fast hits, then 4 hits to the bottom. Again I am not waiting for the bottom plate to get back to vertical. I beginning shooting at it as soon as it is presented enough to make hits.  This pattern and style drives the bottom plate much faster and makes the spinner spin.  Gun and ammo details. KE9 16" barrel using 124gr federal Syntech TSJ factory ammo.

 

Example 3: Starting top plate with Pistol, 2 fast hits, then 3-4 hits to the bottom.  I can consistently double tap the top plate, and triple tap the bottom plate. Gun and ammo details. glock 34 using 124gr federal syntech TSJ factory ammo.

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18 hours ago, Blockader said:

What I was really hoping to get at with this topic was the science and practicality of starting with top versus bottom. That is, the top is a smaller i.e. lighter target and is thus affected more by the round impact than the larger lower plate. Except that the heavier lower target is attached on the end of a "lever" to the lighter upper target so how does that affect the efficacy of shooting the top first? If I owned a spinner I would set a test up to measure the angle of deflection following impact in dead center of each plate. Maybe they are the same, since the two plates are joined, I am not schooled on physics enough to know. If they are the same then starting on the bottom makes more sense since it is larger target. There are other factors as well.

 

With a shotgun, for example, it would seem to me that starting on the lower plate is clearly advantageous, since there is more surface area meaning more of the pattern will impact that plate as opposed to the top.

 

To be clear, my spinner performance is hardly the area I most need to focus on, I just thought it might be interesting to dissect here.

 

If you make a few assumptions, the system becomes fairly easy to analyze. Basically, ignore friction, assume that everything is perfectly rigidly connected, and the draw out the free body diagram. I also, for simplicty’s sake, only looked at the first hit on the target and the amount of angular acceleration that it would apply. In reality the situation is probably more complex since you’re going to be shooting multiple times and the entire system will start to move. 

 

If you define the top plate as having mass M1 at a distance from the pivot of L1 and the bottom as M2 at a distance L2, then the system has a moment of inertia of:

I = M1*(L1^2)+M2*(L2^2)

 

If we shoot the top plate and apply a force of F1, we apply a torque of T = F1*L1. If we shoot the bottom plate, then T=F2*L2 Angular acceleration is

a = T/I

a = (F1*L1)/I or (F2*L2)/I

 

So, if one target is further from the pivot, then we’ll move the spinner more by shooting that target. If the force we apply to one target is greater, for example if we can only get part of a shotgun pattern onto a target because of its size, then the target we can “hit harder” will cause the spinner to move more. The weight of the targets doesn’t matter because they’re rigidly connected- it’s better to think of it as hitting one end or the other of a pivot than as two targets. 

 

I think the real reason to shoot the top plate first is because it’s smaller. In order to spin the spinner, you’re most likely going to have to hit both targets unless you can put it over in two rounds or less. You’re also going to have to switch targets so you’re only hitting them as they’re moving away from you. Since it’s smaller, the top plate is harder to hit, so it makes logical sense to hit it while it’s sitting still so that you leave the larger plate to hit while it’s moving. 

 

At some point it would be interesting to do a detailed analysis of the whole system with multiple hits but it becomes complicated quickly because the forces we’re applying are discrete shots rather than a continuous force. Although, if you assume no friction then angular momentum is conserved, so the problem starts to get a little easier... I might revisit this later if I get bored and have time. 

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Posted (edited)

Unless it is not allowed, for shotgun, #6 Turkey Loads, can spin in 1 or 2 shots.

 

But assuming 7.5 or smaller, same for PCC or pistol, for me it depends on the angle that the top plate is at and distance. I once watched the spinner from almost directly from the side. Several of the shooters were having a hard time moving it on the first shots going for the top plate, it leaned quite a ways back and you could actually watch the birdshot angle/bounce off above it. Once they hit the bottom it moved. 

 

So I look at the angle first, if it is fairly vertical I will shoot the top/smaller plate. If it leans back I shoot the bottom bigger plate. It doesn't matter what gun, double or triple the first shots/plate to get the momentum going, then don't miss with your follow up shots. Biggest reason to have trouble is missing your follow up shots or running out of ammo when it about to go over.

 

gerritm 

Edited by gerritm

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5 hours ago, gerritm said:

then don't miss with your follow up shots 

yeah, how hard can THAT be...

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Seems like from what I have seen is the shooter (ME) focuses on the position of the spinner instead of keeping sight on the plate. Moving your sight based on the plate & timing the shots is key.

 

Also, Murphy's Law is "You will run out of ammo just as the plate is about to go over and need 1 more shot".

 

gerritm

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I shot Berry's Steel Open last week. There were 4 spinners. I used 3 on top and 3 on the bottom. Then needed a couple more to get it over. That was with a PCC sending 115's at ~1200 FPS. That worked for 3 spinners. The last I tried 4 on top and was a bit late on number 4 and wound up dumping some momentum on that one. Unfortunately, it was a 30 second par time stage and it was horizontal when time expired. So, for now 3 on top and what ever else is necessary. 😉

 

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1 hour ago, ChuckS said:

I shot Berry's Steel Open last week. There were 4 spinners. I used 3 on top and 3 on the bottom. Then needed a couple more to get it over. That was with a PCC sending 115's at ~1200 FPS. That worked for 3 spinners. The last I tried 4 on top and was a bit late on number 4 and wound up dumping some momentum on that one. Unfortunately, it was a 30 second par time stage and it was horizontal when time expired. So, for now 3 on top and what ever else is necessary. 😉

 

Last couple we have shot with PCC or pistol I bring some hotter 147 or 124gr factory rounds. Seems to work pretty good.

 

gerritm

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28 minutes ago, gerritm said:

Last couple we have shot with PCC or pistol I bring some hotter 147 or 124gr factory rounds. Seems to work pretty good.

 

gerritm

This was the first match where I successfully dealt with spinners with PCC. 3/4 gave me some confidence. My loads are near 140 PF and I really don't want to mess with the timing of the gun. If I just get a bit more coordinated with my transition to the bottom plate I should be able to do a good 3-4-2 and spin it. I wish I had one to practice with but that ain't happening. I did learn a lot this time. If they would let me, I would bring a shotgun for those stages 😉 Or perhaps shoot my unpleasant open ammo... :roflol:

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11 hours ago, ChuckS said:

This was the first match where I successfully dealt with spinners with PCC. 3/4 gave me some confidence. My loads are near 140 PF and I really don't want to mess with the timing of the gun. If I just get a bit more coordinated with my transition to the bottom plate I should be able to do a good 3-4-2 and spin it. I wish I had one to practice with but that ain't happening. I did learn a lot this time. If they would let me, I would bring a shotgun for those stages 😉 Or perhaps shoot my unpleasant open ammo... :roflol:

 

That same 140 PF with a 147grn bullet will spin it in 1 or more fewer shots I would bet.

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