New (to me) air rifle

I bought this thing off the internet a short while back. It's a cheapo by the way. But pretty powerful it seems.

The first shooting attempts were abysmal. All off hand with elbow touching wall to steady.
I managed to get it to shoot sort of inline but the POI seamed to drift right again.

Well, yesterday I got it inline again it seems to shoot much better (and at further distance - not far though). Offhand I was now getting thumbnail sized groups!
This is surprising because the sights wobble and are very course. I was aiming with those bright dots, not being able to see the rest of the sights.

The pellets were Gamo Pro magnums and these have to be pressed into the breach quite hard so should be a good fit in the bore.

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