What might cause this PoI shift - Huntsman Regal XL

[EPG]

I have a Daystate Huntsman Regal XL .22 unregulated. The rifle is incredibly accurate & consistent.

I was shooting down from a full fill. Shooting 10 shot groups. Seeing if I could keep all 10 shots inside a dime at 40 yards.

I made in through 4 groups - she had put all 40 inside a dime. Shot 41 and 42 were on target…

…I knew I was getting close to when PoI might drop. Shots 43 & 44 went into the same hole - but they went RIGHT !

Shots 43 & 44 would have been inside the dime, if it had not been for the shift right.

Shot 45 was inside the dime, but the PoI had dropped a bit - as expected.

What could have caused 43 and 44 to shift right? It was not the light rain - as they both went in the same hole.

I expected PoI to drop, but not shift. Any experts who have seen this type of thing before? Thanks in advance, Ed

 

[Ranchibi]

I had an unregulated Regal too, maybe the pressure dropped just enough to get both of those shots moving right...could be a right twist barrel as both shots are a smidge low?

 

[Feinwerk]

@EPG ,
Kind of hard to make a judgment based on one single group with 2-3 flyers. How can you be sure there wasn't a little bit of breeze down range?

All it takes is one lead flake stuck in the barrel somewhere or some gunk to start causing flyers. The first thing I would do might be to pull a few patches through the barrel.

In an unregulated gun, as the air reservoir pressure drops, the valve dwell time increases and blows a lot of extra air behind the pellet, possibly pushing it differently as it exits the barrel / air stripper / moderator.

Did your groups tighten back up after refilling your reservoir? Have a look and see if this phenomenon only occurs after 40 or so shots, as your air reservoir pressure drops.

GL,
Feinwerk

 

[elh0102]

When the reg pressure drops enough, then yes, the rifle will obviously shoot low. But as velocity starts to fall (assuming it did), POI can get erratic, and random. I assume it might relate to the rotational speed of the pellet as much as velocity. IMO, this is one of those things hard to explain, and maybe not worth trying. I think the lesson is, your POI will change as the rifle falls away from its set point, so manage your shot count accordingly.

 

[darylm]

Did your scope cool off or heat up? I’ve noticed that most of my poi shifts have to do with the scope temp changing.

 

[MEC17670]

I have a Daystate Huntsman Regal XL .22 unregulated. The rifle is incredibly accurate & consistent.

I was shooting down from a full fill. Shooting 10 shot groups. Seeing if I could keep all 10 shots inside a dime at 40 yards.

I made in through 4 groups - she had put all 40 inside a dime. Shot 41 and 42 were on target…

…I knew I was getting close to when PoI might drop. Shots 43 & 44 went into the same hole - but they went RIGHT !

Shots 43 & 44 would have been inside the dime, if it had not been for the shift right.

Shot 45 was inside the dime, but the PoI had dropped a bit - as expected.

What could have caused 43 and 44 to shift right? It was not the light rain - as they both went in the same hole.

I expected PoI to drop, but not shift. Any experts who have seen this type of thing before? Thanks in advance, Ed

View attachment 276412

You just drop off the sweet spot.
Try doing a complete shot string starting with a full fill, taking notes on shot count and velocity. You'll find the velocity should start lower then climb to where the velocity levels off for the most part, for say 25 shots then the velocity will start dropping. As it drops, due to the harmonics of the barrel, you'll might find a slight poi shift.
Identify the ideal fill pressure , top and bottom, shoot within that range.
My Beman Mako .177 , made by Daystate, has the same problem, but I have found the sweet spots and she's a tack driver.
Hope this helps.