POI change with heat: horizontal???

[bow shot]

So I see that that when I pull my .22 AR out of the cool house (about 66 degrees, near the AC) and start shooting in the heat (about 90 degrees) that my POI will move HORIZONTALY as the rifle warms, and then settle to a 0.5" group (5 rounds) at my original, sighted-in POA (which was established in the heat).

It intrigues me that the group moves so drastically on the horizontal, about 3". Vertical changes about 0.5"

1) Dedicated DPMS (GenII) bull upper.
2) Bushnell Elite 3600 in Larue mount
3) Fed Auto match ammo
4) Shooting from bags, with very good recoil control
5) Zero wind
6) Ammo and rifle stored/moved together, mag pre-loaded
7) Tested several times, the effect is consistent.
8) Testing at 50 yards

Again, the thing that is strange to me is that the POI shifts horizontally (about 3"), only slightly on the vertical.

Anyone else notice a similar behavior with their .22 AR?

 

[patriot]

Its not unusual for the first shot to be high and off to one side half an inch at 50 in a clean barrel. If you chronograph the rounds you'll see an increased velocity. But 3 inches is strange. Is your handguard free floated?

Mark

 

[bow shot]

Its not unusual for the first shot to be high and off to one side half an inch at 50 in a clean barrel. If you chronograph the rounds you'll see an increased velocity. But 3 inches is strange. Is your handguard free floated?

Mark

Yup, free floated. Barrel is very dirty though, likely 500-1K rounds.

 

[dogdude]

My Eley match is the opposite, shoots great in the heat, won't shoot in the cold 55 degrees or less..not good when you shoot indoors during winter

 

[bow shot]

If I can get the time, I'll mount another scope and repeat-test...

 

[bow shot]

Chilly today (67) , the experiment will wait till we hit close to 90 in the day again...

 

[bow shot]

might have to wait on this... papers due for school, OT at work, MOL recovering from surgery...

 

[bow shot]

Between work, school and chores... unable to get back behind the rifle... soon I hope!

 

[bow shot]

Solved: scope mount not clamped down properly. Not down to about 1" drift over temp change, and keeping about 0.5" if I shoot well.

Thanks folks