The biggest reason for a pellet to corkscrew, is that the head size of the pellet, is either too big or too small for your barrel.
I have a Steyr LG110 FT. I had great accuracy at short range, from like 10 to 25 yards. My best groups at 50 yards were like 5" to 10" group. At first I thought the barrel was dirty, and I would clean it untill I got a clean patch. Unfortunately it had no effect.
The pellets that I was shooting had a 4.52 head size diamator
then I saw the pellet sorting that Ted Bier did on Youtube, I went and bought different head size pellets in JSB. 4.50, 4.51, 4.52.
The berrel had it's best accurate groups with the 4.50 pellets. Now I shoot sub .2" groups at 50 yards.
Finally I have the accuracy that I have been expected from my rifle.
Biagio