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*Optical phenomenon* or a curved barrel - pellet flight starts off center - SOLVED

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A

Adop

Member
Nov 26, 2022
36
23
Baton Rouge, LA, USA
I was setting up my OrionCam with firefly (10/10 recommend) when I noticed the pellet first comes into frame far to the right (further than the windage). I am shooting JSB 15.89grs at 914 fps from a Daystate Regal XL with Hawke Sidewinder 4-16x SFP scope with half mil ticks (true mil at 10x), mounted on UTG medium rings. Two clips below.

Clip 1: Shooting paper at 20 yards with a 20 yard zero, very little wind, 10x magnification. The pellet enters frame about 2 mils to the right, I thought it was scope cant and realigned the scope. The scope cam wasn't lined up or focused properly yet so ignore the tilt in the video.

Clip 2: A different day. I zeroed at 20 yards and dialed 0.7 mils up and 0.5 mils left to shoot the target at 50 yards. The wind was spiraling but the shots were consistent once dialed in. I don't remember if I was shooting at 10x or 14x magnification in this video, so here's the math for all of it: Pellet enters frame 4 mils to the right - at 10x this suggests I either misjudged the wind by 22 mph and was dialed 4 mils not 0.5, or there's a ~20 degree cant in the scope, neither of which are true. If this video was taken at 15x, that would translate to the pellet starting 2.7 mils right on a 10x magnification, which mean I misjudged the wind by 15 mph..

Anyone know what's going on here?


PS: I'm still getting the camera focused in these clips so don't judge the quality - the scope cam is great :)


 
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Gerry52 said:
Have you indexed your barrel to make sure pellet is leaving the gun CENTERED with the windage crosshair? That's a strange phenomenon. It sure is hitting where you aim though.
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I haven't indexed it. I'll have to look into how feasible that would be to test with the Daystate Regal. Does this look like a reasonable amount of barrel curve? It feels like a lot..
 
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The reason you were experiencing that phenomenon was because although the parallax at the target's distance was corrected, the camera lens wasn't looking through the scope at its center. You can easily observe this by removing the camera and looking through the scope yourself. First, focus on a target, say 30 yards, and make sure there are objects much closer than the target that can also be a part of the sight picture for reference. Then, move your head side to side while looking through your scope but at the same time paying attention to the out-of-focus objects before the focused target--you would see them move off center. So if you think of your camera's lens as your eye instead at the time of the video recording, therefore, your eyes or line of sight wasn't concentric with the ocular lens.😉
 
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spinj said:
The reason you were experiencing that phenomenon was because although the parallax at the target's distance was corrected, the camera lens wasn't looking through the scope at its center. You can easily observe this by removing the camera and looking through the scope yourself. First, focus on a target, say 30 yards, and make sure there are objects much closer than that that can also be a part of the sight picture for reference. Then, move your head side to side while looking through your scope but at the same time paying attention to the out-of-focus objects before the focused target--you would see them move off center. So if you think of your camera's lens as your eye instead at the time of the video recording, therefore, your eyes or line of sight wasn't concentric with the ocular lens.😉
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That is an interesting explanation. So I could test this by intentionally offsetting the camera position (or angle?) to the opposite side to see if pellet appears to originate from the left instead of the right.. And with a perfectly centered camera this phenomenon would go away?

I do much prefer this possibility to a curved barrel :LOL: I'm curious how often any of the other scope camera guys experience this. I don't recall ever seeing this in any youtube videos unless they're dialed for a ton of wind long range.
 
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I test my laser sights using a scope mounted on the gun or an optic not mounted on the gun. I have noticed that the lower velocity projectiles do curve using the gun mounted scope more than the optic. Some of that visual is the position line that the projectile is being viewed from. As with a baseball pitcher throwing curveballs, wouldn't the rifling and velocity have the same effect? I do agree that the lens curvature can cause visual distortion if the lens is off-center. And I have noticed visual shift moving my head side to side as well. The laser targeting does stay consistently on while the crosshair does appear to change position. I have been wrong more times in my life than I have been right, so please feel free to correct me.
 
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Well I can promise you my gun isn’t throwing curveballs. I can’t slow down the frames slow enough to show exactly what the gun does the instant my hammer strikes. I can see overall recoil just can’t break it down that far. His first video definitely looks like recoil. Second video is a little more perplexing. Either way his gun is dead on so really nothing to worry about.
 
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Vetmx said:
Well I can promise you my gun isn’t throwing curveballs. I can’t slow down the frames slow enough to show exactly what the gun does the instant my hammer strikes. I can see overall recoil just can’t break it down that far. His first video definitely looks like recoil. Second video is a little more perplexing. Either way his gun is dead on so really nothing to worry about.
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In the first clip there is a single frame where you can see the pellet starts ~1.5 mils to the right.
The thing with the gun being dead on is that I dialed the turrets to that distance and trial and errored the windage. I assumed at the time that my windage was actually due to the wind.. but it could also be that I dialed for barrel curve or an off-center optic (or something else?). If it's not the parallax/optic theory with the scope camera then I find it difficult to trust this gun hunting when I only have one shot and need to trust the the ballistics.
 
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MRaccurate said:
I test my laser sights using a scope mounted on the gun or an optic not mounted on the gun. I have noticed that the lower velocity projectiles do curve using the gun mounted scope more than the optic. Some of that visual is the position line that the projectile is being viewed from. As with a baseball pitcher throwing curveballs, wouldn't the rifling and velocity have the same effect? I do agree that the lens curvature can cause visual distortion if the lens is off-center. And I have noticed visual shift moving my head side to side as well. The laser targeting does stay consistently on while the crosshair does appear to change position. I have been wrong more times in my life than I have been right, so please feel free to correct me.
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While there might be some curve to the shot I don't think it explains how the pellet is THAT far to the right just a few yards out when it first pops into the scope. The first clip would be >.72 inches (>1 mil) of curve in just 20 yards on a calm day with 16 gr pellets.

I had to look up barrel indexing too: barrels are curved ever so slightly and it leads to consistent POI shifts at long range. You can rotate the barrel and shoot groups with it in different positions to find out which way it curves. Most people set the curve going up and down so they don't need to worry about the left to right stuff.
 
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Adop said:
While there might be some curve to the shot I don't think it explains how the pellet is THAT far to the right just a few yards out when it first pops into the scope. The first clip would be >.72 inches (>1 mil) of curve in just 20 yards on a calm day with 16 gr pellets.
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While pellets, like all spinning projectiles, do fly in a curved trajectory, the effect is minute over ranges of 20 yards. The sights will be pointing slightly to the left to take account of the drift, but nowhere near enough for the effects shown.
 
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Adop said:
In the first clip there is a single frame where you can see the pellet starts ~1.5 mils to the right.
The thing with the gun being dead on is that I dialed the turrets to that distance and trial and errored the windage. I assumed at the time that my windage was actually due to the wind.. but it could also be that I dialed for barrel curve or an off-center optic (or something else?). If it's not the parallax/optic theory with the scope camera then I find it difficult to trust this gun hunting when I only have one shot and need to trust the the ballistics.
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This is where I believe you are getting thrown off. Your pellet doesn’t start at 1.5 mils to the right because we can’t see the end of your barrel. When the pellet comes into frame it’s 1.5 mil to the right but a lot harmonically has happened before that.
 
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