Mini-14 sight in groups vs pattern

[Dark Horse]

A buddy picked up a Mini14 Thursday. This past Sunday we attempted to sight it in.

We started with a quick function check. Everything was tight and good to go.
Rest was a stony creek long bag
Target was "shoot n see" 12" circle
Remington Express Core-loct 223 Factory ammo was used though out. The last 5 shots were Federal American eagle to rule out an ammo issue.

@ 25 yards 2 shots 1 in 9ring, one in 10

Moved to 100yds.

1st shot 8 ring left

2nd 10 ring

3rd off target 1/2" to the right

Rear sight is loose, by 1 full turn.

Tighten rear sight. Double check the lock screw, everything is tight

Now we are getting a shotgun type pattern covering the entire target + 2" of paper surrounding the target - rear sight is checked every round for the next 5.

Try 5 more no change.

Rear sight is loose again.

I've never had to lock-tite a sight screw before. But even before it was loose, we were not getting anything even remotely close to a grouping beyond the 25yd test to see if the sights were close out of the box.
Other than this the rifle ran like clockwork.

Any one have any thought?

[gokyo]

it is a mini 14 I would expect it to shoot about 4+ inch groups at 100m

But I have pretty low expectations for the rifle.

[Dark Horse]

I was not expecting sub MOA accuracy. I was figuring 2-3" give or take, not 14+" That's what surprised me The fact the rear sight kept coming loose was frustrating beyond words.