would scope cant cause this??

[cummins cowboy]

YouTube - SHLowlight's Channel

this guy is doing a review on a scope I noticed that as he moves up further in elevation the groups moved down and to the left, I am wondering if say a 3 degree scope cant could cause that sort of error??

 

[Gunpoor]

It was either wind drift or the scope not being mounted level, and I believe the cant is what is causing the groups to drift left.

 

[Ldwillie]

Hmmmm...... I have a similiar question. I am typically shooting a .243 win with 100 gr Speer BTSP, but for fun I reloaded some 58 gr Vmax for coyote hunting. When I went to the range to test them out I noticed that I was high about 2 inches and to the right about 1.5 inches. Of course the elevation makes sense with it being almost half the weight of the 100 gr, but why would they be going right? Also, on the same day, I was playing with a big gong at 300yards. In order to hit about where I was intending, I had to hold high of course.... but also about 12 inches to the right. Some wind that day would be part of that but not for 12 inches worth. Does anyone have any ideas on what is going on? Would it be the scope being canted that caused this result? Or could be it be my 1:9.25 twist is not stabilizing the 58 gr.? How could I tell the difference? Of course any insight is greatly appreciated
LDW

 

[Gunpoor]

When bullets are changed internal ballistics change also and that includes barrel harmonics. A rifle barrel is not stationary during firing, the barrel whips in a figure 8 pattern that is not noticeable to the shooter or onlookers. The exit from the barrel may not happen at the same place during this minute barrel dance causing a different POI. If your rifle groups well at 100 yds and the group moves 12" horizontally at 300 I would attribute this to wind drift. Small/light bullets will drift easily with the wind. I have found that out shooting prairie dogs with light bullets with small bore rifles.

 

[Ldwillie]

Ah, that makes sense So does that mean that I would have to completely re-zero each time I try a different grain, as opposed to just adjusting my elevation?

 

[Gunpoor]

You got it. That is why I shoot one bullet in one rifle until I think I need to go to something different. It is whole new load workup and then reset the scope. I have heard and seen some differing loads that shot to the same POI, but that is not the norm.

 

[Ldwillie]

Thanks for the info! I am glad that it is not scope cant I guess I will just zero my gun for coyote season, then again for deer season. I need the practice anyways