Possible Pulsar POI issue or can someone explain this to me?

F

Farmer8430

New member
I missed a coyote the other night, video showed a dead center hold on its chest, it was within 130 yards. I checked my zero tonight and it was dead on at 50 for the 1st shot. Let the scope sit on outside for 35 minutes shot again. Dead on at 50. Decided to double check and brought the target out to 125, shot once and was 5 inches high and 2 to the left, brought it in to 75 and you can see the shot in the picture. Brought it back out to 125 and as the picture shows one was touching the first and just below on the next one. Nice group just way off. So whats going on here? Have not changed my zero since last winter, had been on and was killing coyotes with no issue. Even had a 230 yd one where I hit my POA. Shooting a 6.5 grendel, 123gr hornady sst. I have always zeroed at 50 and had been accurate on paper out to 200 before.
Why would it be that bad?
20211019-012854.jpg
 
Did you increase the zoom between 50, 75, and 125? On some thermal scopes that will affect poa/poi.

Different scope, but just yesterday I helped a buddy zero a IR Hunter MK111 60mm on a 6.5 Grendel. At 25 yards he was dead on, about 4-5" high at 100. We zeroed it at 100.
 
Did you increase the zoom between 50, 75, and 125? On some thermal scopes that will affect poa/poi.

Different scope, but just yesterday I helped a buddy zero a IR Hunter MK111 60mm on a 6.5 Grendel. At 25 yards he was dead on, about 4-5" high at 100. We zeroed it at 100.

Double post, sorry.
 
Last edited:
Yes it is a trail, forgot to add that. Last time I had a day scope it was dead on at 50 and a little bit high at 100 and good at 200. Its always been an accurate rifle for me, no issue hitting crows at 200 yds.
The zoom was at 6.4 at all 3 distances. I can put then day scope on and check it again. I will also try zeroing it at 100, I just wanted to check here before I changed anything to see what everyone thought. Peoples past issues with pulsars has me nervous, and it doesnt make sense to me that earlier in then year I did not have these issues even at longer distances
 
Zero at 100 and check at 200. A lot of guys zero at 50 but IMO that should just be a starting point.
 
I had nothing but poi issues with the 3 trails I had but I would probably stick to 100 yards to see if it’s definitely the scope. Unfortunately I think you might be in for a ride with that trail. I hope I’m wrong. I have noticed when i sight in other guns and scopes for 2 inches high at 100 yard target and then shoot at a 25 yard target, I will hit half inch or so low under my point of aim. I think it has something to do with how high a particular scope sits off of the barrel but I’m no ballistics expert so I really don’t know why. The fact that it seems to be hitting consistently at certain yardages is somewhat reassuring. My trails would be off 3 to 4 inches at any given time at 100 yards. It was pretty frustrating. If it’s not holding zero and you return it and it’s under warranty and you push hard enough they will probably replace it with a Thermion. That process takes time so might want to try to figure it out sooner than later.
 
Last edited:
Thermal scopes tend to sit 2.5" or higher above bore. My Super Yoter with a riser sits over 3.3" above bore because I have it on a 5/8 riser. The description and zero presented seems drastic but isn't as drastic as one may think. People have grown accustomed to things with a glass scope. Starting at 1.5" over bore vs 3" over bore makes a big difference.

I took the data you supplied and put in a 6.5 grendel 123 gr hornady load in the hornady ballistics calculator. You were a little high at 50. I realize it is close but the closer you zero, the more particular this becomes. You are also a little left of target so that continues to be amplified as the distance grows. Check out the chart below.

zero_50.jpg


If you measure straight down as to the elevation change, it looks like it might be around 4". This chart shows with a 40 yard zero (slightly high at 50) and 3" above bore scope, this isn't very far off. It is showing 3.3" at 125 and 3.5" at 150, so some slight differences and you could be right there.

The advice many have given which is zero at 100 is very wise. At 50, due to your height above bore, you bullet is rising way too fast and high through the majority of the kill area.

Here is another common issue that I have gotten myself into and am changing over time. Most night hunters unless they live in heavily wooded areas probably kill their coyotes between 75-150 yards. However, many people will sight their thermals in for 2"+ above at 100 yards. They do this because from a ballistics standpoint they want their PBR to extend to 275 or 300 yards. That is fine, but what you are actually doing is shooting way too high for most of your coyotes through the 75-150 range.

In the example shown above, the bullet is 2 to 3.5" high through the majority of the shots. To me, it doesn't make sense to be shooting that high for the rare 300 yard shot. I have actually brought my POI from 1" at 100 down to around .5" high at 100 for my 22-250 after I elevated my scope another 5/8"
 
I guess I will have to try mine at 175 and see if it’s hitting higher than 2 inches above point of aim. . I just figured the 2 inch high at 100 was the cushion I needed for the bullet drop between 100 and 225 yards or so with a 223. Didn’t realize it would keep coming up after 100. By looking at that chart it appears that it does. Maybe I’ll just put it dead on to half inch high at 100. I don’t usually shoot over 200 anyway.
 
Last edited:
Originally Posted By: Kirsch
Here is another common issue that I have gotten myself into and am changing over time. Most night hunters unless they live in heavily wooded areas probably kill their coyotes between 75-150 yards. However, many people will sight their thermals in for 2"+ above at 100 yards. They do this because from a ballistics standpoint they want their PBR to extend to 275 or 300 yards. That is fine, but what you are actually doing is shooting way too high for most of your coyotes through the 75-150 range.
Thats why I switched from 18 inch barrels to 24 inch. I would estimate yardages and sail over the top of coyotes at closer ranges. Now I don’t need to deal with the arc.
 
Originally Posted By: Dark moon 63Thats why I switched from 18 inch barrels to 24 inch. I would estimate yardages and sail over the top of coyotes at closer ranges. Now I don’t need to deal with the arc. Darkmoon, what I believe you are saying is by using a longer barrel, you are gaining speed, making it a flatter shooting gun. There is validity in saying faster is flatter. From everything I have read, a person can get around a 160 fps increase by going with a 6" longer barrel. This isn't always the case as shown by this article..

If I plug in a 160fps increase in the same load data, it actually made the load shown above increase in height through the standard coyote kill zone when zeroed at 40-50 yards. Due to the extra speed, the bullet's highest point of the arc was reached further down range making it even higher through the sweet spot. It just reaffirms not to use a really close zero with a thermal because of the height most thermals are away from the bore.

A bullet doesn't actually rise. It is a perceived rise because a person is pointing the barrel at a higher angle. Gravity is always pulling at your bullet and it is always falling. It just happens further downrange, the faster your bullet is and the higher you aim.
 
I don't know what your actual issue is but close in zeros, such as 25 yards, 50 yards, etc., means the bullet will continue to rise due to the super elevation of the barrel, as mentioned by Kirsch, and the rapid intersection of the bullet's path and the aiming devices line of sight.

The closer the INITIAL intersection (in your case 50 yards), the higher the bullet will rise. Eventually, the bullet will come back down through the line of sight creating two zeros, a NEAR zero and a FAR zero. The max rise in that established arc between the NEAR and FAR zero is called the Max Ordinate, an artillery term.

The only thing I can think of that would create a windage drift such as yours is the aiming device's line of sight is not aligned with the rifle's bore. Any offset, no matter how minor, will be exaggerated at distance, just like when using a laser aiming devise that's offset to the bore.

Seems to me a 50 yard zero should be slightly high at 125 and darn near back on at 200-225. A ballistics chart and field testing will give you SPECIFICS.
 
I agree a bullet doesn't climb but the angle between the cross hairs and bullet path make it look like it does. The closer zero under a 100 yds and higher the scope makes the angle sharper. The bullet hasn't dropped enough to meet the crosshair angle say with a 50 yd zero impacting at 100 yds. Giving the appearance of a climbing bullet and a missed coyote. I would zero 2" high at 100 and be a little low at 200. That was my arc. Now I zero at 100 and drop 1/4" at 200. My 18 inch 6.5 Creedmoor with 95 gr. Vmax was the worst.
 
Originally Posted By: Dark moon 63I would zero 2" high at 100 and be a little low at 200. That was my arc. Now I zero at 100 and drop 1/4" at 200.Agree, this makes way more sense.

The point everyone needs to realize is when using a ballistics table/chart/program make sure to measure your height above bore with your thermal. This changes numbers significantly to what most people have grown accustomed to.
 
...the topic of POI calibration point 0 is very interesting. I did not understand everything you have written guys, but of one thing I am sure ... that, due to the distance between the axis of the thermal device and the axis of the barrel, it is better to calibrate the zero at 100 yards, in order not to have excessive over elevation at distances between 50 and 250 yards. I ask you then ... wouldn't it be better to set 0 at 150 yards? What would be the advantages and disadvantages of this choice?
 

When I first read of your scope problem, my mind instantly went to a previous scope I had. Back in the day before thermal, my first night vision experience was a Gen 1 scope for use at a bait site. That thing was huge and heavy as an anvil, and it sat pretty darn high above the bore. My bait site is 60 yards from my hunting shack, so I would adjust for a dead center hold at that distance. I dropped several coyotes that way, but later found that trajectory was a real issue if shooting at greater or shorter distances. Like Korey mentioned, we are accustomed to trajectories of lower riding daytime scopes, and switching to a higher sitting scope changes trajectory a lot. While my scope was lights out on coyotes at 60 yards, when I went to 130 yards I shot 2” high, and 2” low at 25 yards. It sounds as though you may be experiencing similar.

One thing you might try is to do a ballistic chart like the one Korey posted, for your particular rifle and load. Chronograph your load for velocity, then use a ballistic program (probably one available online) to determine bullet impact at various distances. You have to enter the ballistic coeficient of the bullet, bullet weight, muzzle velocity and scope height above the bore. If you set zero in the program at 150 yards as you mentioned, the chart will show bullet impact at other distances. Fire a few rounds at various distances to confirm the chart’s accuracy. With a chart that matches your load, you can play around with zero range to get the kind of trajectory you want.

 


Write your reply...
Back
Top