Baffled with POI Change!

[Horniac]

Really sounds like you bumped the scope somehow from the time you were at the range to when you were hunting. With a 200 yd zero, there is no way you should be 4 minutes low at 350. Even if one box of ammo is 100 fps slower it wont put you 4 minutes low. Take it to the range again and run it repeatedly back and forth between your 200 yd zero and 500 yd elevation maybe for 20 rounds or so. If you continually hit the targets then it likely got bumped. If for some reason it doesnt repeat, then you have an issue with the scope. I got my 26 out yesterday for the second range session. Shooting 120 E-tips over Retumbo. Three 5 shot groups were 0.7, 0.9 and 0.9 MOA. May give it a shot if the factory ammo doesnt work out for you.

Tankgijohn72 thanks for your input! I am starting to rule out the ammo since I recalled that I sent an Accubond downrange and had the same low impact. When I was last at the range I was going back and forth between 200 and 300 yards and getting consistent tracking. I wasn't able to go out any longer distance because the 500M range was unfortunately closed that day. Glad to hear your getting some good groups with your E-tips. I'm shooting some custom loaded ammo that I'm very happy with since I had to change to a copper bullet so hopefully the POI shift has nothing to do with that. I think I have already went through 4 of my 8 boxes of this ammo so hopefully I will have some left (and a barrel) by the time I get things figured out haha!

Horniac

 

[Mike 338]

I'm thinking your range isn't close to where you hunted. Altitude, Temperature and Angle of shot are huge factors. In theory, the KILO should have spit out a ballistic solution but there could be something off in that department. "Pressure" is sort of a big confusion but important enough to cause a miss if it's not programmed as it should be. "Zero Altitude" is important if you sight in at one Altitude and hunt at another. Also, anytime you can, set up a can or something in the general area your hunting and take a poke and see if your rifle is on, do it. Your in good company. POI shift is very common from range to where you hunt although most misses are high.

 

[Horniac]

I'm thinking your range isn't close to where you hunted. Altitude, Temperature and Angle of shot are huge factors. In theory, the KILO should have spit out a ballistic solution but there could be something off in that department. "Pressure" is sort of a big confusion but important enough to cause a miss if it's not programmed as it should be. "Zero Altitude" is important if you sight in at one Altitude and hunt at another. Also, anytime you can, set up a can or something in the general area your hunting and take a poke and see if your rifle is on.

Mike 338 thanks for your help. I am going to shoot my gun next time at my hunt area just to make sure nothing has changed during the trip. I understand the atmospheric variables can change the ballistic solution but from playing around with my ballistic apps it would be very minimal and nowhere near the 4 MOA shift I experienced...

Horniac

 

[Horniac]

I'd do a tall target and scope tracking box test.

Joefrazell thanks for your recommendation! I just found a Youtube video on the test you are suggesting and am looking forward to watching it and seeing if I have the range facilities and equipment to give it a try...

Horniac

 

[Laelkhunter]

The rifle is a 1/2" moa rifle so at 200 yards the 3 shot 1" group was averaging 1/2" low.
Just trying to make it perfect. Isn't that what this is all about?
But chances are that if something was stuck internally, it would have let loose eventually and did what happened to the OP.

Great shooting and a great shooting rifle !! No harm meant, it was a serious question as to the group size at 200. My rifle shoots the 225 Barnes TTSX into 1/2 to 3/4 inch groups at 100, but at 200 they don't stay at moa (old age is hell), and if I was 1/2" low, I would call it good and go hunting. All of my hunting (Elk) is usually done between 100 and 200 yards.

 

[Mike 338]

Mike 338 thanks for your help. I am going to shoot my gun next time at my hunt area just to make sure nothing has changed during the trip. I understand the atmospheric variables can change the ballistic solution but from playing around with my ballistic apps it would be very minimal and nowhere near the 4 MOA shift I experienced...

Horniac

Shot Angle?

If your range is from a elevated position in relation to your target and your hunting shot wasn't, that could account for a very low shot.

Also, when you were at the range sighting your gun in, were you resting the "barrel" on the sandbags or was the fore-stock on the sandbags? I pretty regularly see folks resting the barrel on their sandbags or whatever rest they're using and this will cause an extreme POI shift.

 

[Horniac]

Shot Angle?

If your range is from a elevated position in relation to your target and your hunting shot wasn't, that could account for a very low shot.

Also, when you were at the range sighting your gun in, were you resting the "barrel" on the sandbags or was the fore-stock on the sandbags? I pretty regularly see folks resting the barrel on their sandbags or whatever rest they're using and this will cause an extreme POI shift.

Both my hunting shot and the range were flat within a few degrees of one another. The KILO ballistic solution takes the shot angle into account. Even at an extreme angle like say 33%, the most I would be off would be like 1/2 MOA but I'm 8X that amount at 4 MOA when I checked it on paper at 200 yards.

Also, I was resting my fore-stock on my pack in both instances so I don't think it's that.

Based on everyones input, I am coming to the conclusion that either my scope somehow got bumped or something got temporarily hung up in the erector tube. Hopefully it won't happen again and thank you everyone for your help!

Horniac

 

[Uboatrobert]

I was hoping some of you experienced shooters on here would be able to help me with a problem I encountered with my gun that has me baffled as follows;

I had a rifle built in 26 Nosler. I have a Huskemah Blue Diamond 5x20 scope on it with a turret built for the 140 gr Accubond. Because our state is outlawing lead bullets, I am switching to copper. However I was unable to find any factory ammo that I could readily purchase with a copper bullet so I turned to a company that custom loads ammo. They had worked up a load in a Fierce 26 utilizing the Barnes 127 gr LRX BT and found the tightest groups at a MV of 3393 fps so I ordered 4 boxes to try out in my gun. They actually grouped better than the Accubonds. So I re-zeroed to be dead on at 200 yards and shot it out to 300 yards on my first range day. The next time to the range after entering the profile in my Sig Sauer Kilo 2400 ABS I shot the 500 meter range and was consistently knocking over the steel sheep, pigs, etc between 200 meters and 500 meters. Out to that range the turret yardage markings were still good though I was getting the output from the Kilo in MOA and counting clicks. I thought all was good and so with the 12/31/17 deadline for receiving on-line ammo in CA (don't get me started) I bought another 4 boxes so I would have it for future hunts.

Here is where the problem started. On a hunt two weeks later I had an animal broadside at 350 yards and completely missed and missed him again going away at 450. I was at a loss as to why I had completely missed as to I never fell on the hunt, bumped my scope, etc. Once home, I went back to the range and now I couldn't hit anything between 300 and 500 meters. I was by myself but shot video through my phone scope and it appeared I was hitting consistently way low. Another shooter came over and spotted for me and confirmed I was way low. When I explained how I got to this point he suggested I check the scope tracking with a Collimator. He said if the scope was tracking erratically you would see the grid in the Collimater appear to jump all over as you dialed the turret up and down. Appreciative of the advice and hoping that this would be my problem, I left the range and went home and checked the tracking through my Collimator. All appeared in order. In addition I checked the torque on all the action screws, rings, etc. but didn't find anything out of wack. Back to the range I went and shot my first group at 200 yards. The group was 4 MOA low. I re-zeroed accordingly and shot it out to 300 yards going back and forth on the turret between my 200 and 300 yard target to see if there were any changes in the point of impact. It all seemed good now.

So now I have an explanation as to why I most likely missed on my hunt, but have no explanation as to what caused my point of impact to change by 4 MOA so I have lost all confidence in the gun until I can find a plausible reason. I was hoping to get some input from you experienced shooters on what might of have caused this as the only things I can come up with are as follows; 1. the turret somehow hung or something but then tracked normally again after misaligning by 4 MOA or 12 clicks on my scope (I don't know if this is even possible). 2. the turret somehow loosened and was set back down on a different yardage (though I don't see how as it seems you have to basically take the screw completely out to raise the turret to set it back down) 3. unbeknownst to me the scope was somehow banged or jarred to move the point of impact 4. barrel fouling changed the pressure and therefore the group point of impact but this seems unlikely to me based on the amount of point of impact shift. Note I didn't clean the bore between any of the sessions or before my hunt.

Thanks in advance for any ideas/help in troubleshooting my problem...

Horniac

 

[Uboatrobert]

Re the custom loads question....unknowing to you, the 2nd order of ammo could have been from a new canister of powder, which different results can occur. I have had this happen twice on 2 different rifles and had to re-group and change my loads and scope settings. I will not knock a Custom Reloader, but in doing it myself, I find I have better control of the accuracy.

 

[Horniac]

Re the custom loads question....unknowing to you, the 2nd order of ammo could have been from a new canister of powder, which different results can occur. I have had this happen twice on 2 different rifles and had to re-group and change my loads and scope settings. I will not knock a Custom Reloader, but in doing it myself, I find I have better control of the accuracy.

Uboatrobert, thanks for your input. How much of a POI shift have you had with different canisters? That would relate to muzzle velocity then which I would think I could check with a chronograph that I unfortunately don't own at this time. I have thought of that, but have since ruled that out after recalling that when I was at the 500M range I sent a factory 140 gr AccuBond downrange with the same low POI. Also, I when I entered a minus 4 MOA at 200 yards in my ballistic app for truing the muzzle velocity it would not compute and gave me an error. It just seems like too great an error unless they were loaded with half the powder or something. And again, I come back to the same low POI with the AccuBond albeit only one shot at the 500M range. I guess a way to verify without a chronograph would be to go back to the 200 yard range now and shoot the factory Accubond's again and see if they are printing close to my now re-zeroed rifle. If so, I would think I could safely rule out my custom loaded ammo as the culprit...

Horniac

 

[Uboatrobert]

Uboatrobert, thanks for your input. How much of a POI shift have you had with different canisters? That would relate to muzzle velocity then which I would think I could check with a chronograph that I unfortunately don't own at this time. I have thought of that, but have since ruled that out after recalling that when I was at the 500M range I sent a factory 140 gr AccuBond downrange with the same low POI. Also, I when I entered a minus 4 MOA at 200 yards in my ballistic app for truing the muzzle velocity it would not compute and gave me an error. It just seems like too great an error unless they were loaded with half the powder or something. And again, I come back to the same low POI with the AccuBond albeit only one shot at the 500M range. I guess a way to verify without a chronograph would be to go back to the 200 yard range now and shoot the factory Accubond's again and see if they are printing close to my now re-zeroed rifle. If so, I would think I could safely rule out my custom loaded ammo as the culprit...

Horniac

 

[Uboatrobert]

Back to you......as to the powder changes happened awhile back, I think the shots were low somewhere about 4 to 7 clicks and only 1 had been chrono'd. Since then, I sold that rifle to a friend. Believe me when I say that powders change from batch to batch, and it is prudent to check a New batch w/about 10 loadings to learn the differences.
I am now 88 and have been loading since I was 13....started with a 22 Hornet, and have seen and learned a lot.