Scope problem.

[eighteenninetytwo]

Took AR to range. Zeroed in at 50 yards. Got three bullets into one large hole - Fine thinks I this is great. but then the next two of the group were also in one hole - but about an inch away. fired another 5 shot group at another point again 4 this time in one large hole, POI same relative to POA as the last two shots of first group. this happened again later.

I was using an El cheapo 2nd hand old scope (millett) and it seems that the internals are not staying put, but the rifle itself seems to be nicely consistent. Anyone heard of this before with a dodgy scope? Also I need a recomendation for a scope for AR up to about 10x magnification to fit an RRA mount - tube diamter is an inch I think maybe 25 / 26 mm. budget is up to about $300. ideas?

[Black Majik]

So, your POI is changing but still grouping?

Weird. Do a box text and see how well the scope is holding up. BTW, what Millet scope and mount?

[saber]

I had a similar problem with my Millet DMS and the problem was that one of my rings were loose.

You might want to check your mount and rings.

[igorts]

similar happened to me.
group at 50 was 3/8" one day, next day moved to 100, had to re-sigh in due to scope move.
shooting 10 rounds, first 7 within 1" than 8th is 1/2" down, 9th is another 1/2" down, so goes last one.WTF? scope? barrel? me?

[qaz987]

Saber's right, something's loose. Internals, rings, or mount.

[ar15barrels]

Besides a loose mount, also look at Parallax as being a cause.
If your cheekweld changes and the scope is not parallax free, your group moves around on target.

Otherwise, it's just a bad scope.
Bad scopes are not uncommon in cheap brands.

[eighteenninetytwo]

the reason Ithink it's the scope internals are that befor ethis when first zeroing I had to move it about 20 clicks to make it move the POI down about an inch, but the windage appeared to be about right - ie 4 clicks to 1/2 inch at 50 yards.

[ar15barrels]

the reason Ithink it's the scope internals are that befor ethis when first zeroing I had to move it about 20 clicks to make it move the POI down about an inch, but the windage appeared to be about right - ie 4 clicks to 1/2 inch at 50 yards.

That's a sure sign of a broken erector spring.
Give the scope a wise wack with your hand between shots.
If the POI shifts with each wack, the erector spring is broken.