Rifle Scopes Massive shift in POI

[Nik H]

Hi All,

This one has me scratching my head and hoping someone out there can give me some ideas. I need to give you some background

Rifle: Anschutz MP64
Ammo: Prime Bolt Action
Scope: SWFA SS 3-15x

We had a tournament today at my local club shooting small steel targets at 100 and 200 yards. Last Sunday I went out to ensure my scope settings were correct. Fired a total of 100 rounds at 100, 150 and 200 yards. Temperature was low 70s. Humidity was low and wind was 5 -6 mph as measured by the Kestrel. Scope is zeroed at 50 yards. Confirmed zero last week. Unlike many I have not set the scope elevation dial to 0. The scope dial at a 50 yard zero is 2.4 mils as it always has been. Targets were bullseye. Groups were very consistent at all ranges.

Dial settings on the scope at other ranges were as follows:

100 yards - 4.4 mils
150 yards - 6.6 mils
200 yards - 9.4 mils

Got to the tournament today and had 45 minutes to take some practice shots (thank God!). At 100 yards we were shooting circular, metal reactive targets ranging in size from 3 inches to 1 inch in diameter. At 200 yards we were shooting prairie dog reactive metal targets about 6" tall and 3 inches wide. Temperature was 88 degrees. Wind was essentially zero mph. I shot 5 practice rounds at the 3" target at 100 yards and missed every one. Spotter saw no splash. I freaked out. Checked the scope tightness and it was good. Fired five more and had 5 more misses. My buddy said calm down...makes no sense. Tried aiming at the midpoint in height of the berm and my spotter saw the splash at the TOP of the berm. I dialed down 3.9 mils and the splash was exactly at POA. Fired 10 shots at the reactive targets and hit 9. WTF!!! Have no clue how to explain a change of 3.9 mils at 100 yards.

Tried 200 using the setting of 9.4 mils on the dial....same thing. New setting to get POA and POI to agree was exactly the same 3.9 mil shift. Dial now read 5.5 mils versus 9.4 mils.

Ended up winning the 200 and 2nd at 100 yards. Everything appears totally tight...rings to scope and rings to dovetail rail...

Ammo is from identical lot.

I am all ears

Thanks in advance.

 

[redneckbmxer24]

Why didn't you take a minute to zero out the knobs? Since you didn't zero them, do you know that the set screws are definitely tight where they are? If you don't that's a huge variable as they could be slipping.

I would not trust a dirt splash in a berm to be an absolute, the 3.9mil could easily be a little more or less. Have you shot it on paper since to get precise verification?
Are you positive that you didn't just get off a revolution?

You need to eliminate the variables before you can check reliability of the optic. You should rezero and zero out your turrets and make sure the set screws are properly torque. Then see if the problem repeats itself and go from there.

 

[Nik H]

Thanks for the reply

Nothing slipped...Not off in a revolution...you are right in that it may be 3.8 or 4.0. I checked tightness of the dials and the rings with a torque wrench there.

I will test on paper tomorrow but don't see the point. If I am hitting a 1" plate at 100 yards consistently with the new setting, then it would make no difference on the paper to my mind.

It is clearly weird but I will try on paper

 

[fmaglin]

I had a similar happening with my SWFA fixed power scope. Contacted SWFA for a replacement. Sent me a new scope. Problem resolved.

 

[Tcoddington]

Not sure happened but I would consider sending it back either way. Congrats on the good finish.