ORIGINAL: mcawful
here's a handy barrel twist chart for quick reference...
http://www.thebuckskinner.com/barrel_chart.html
On here it says that the White Mountain has a 1:28 twist. Have you considered that the barrel on the rifle may not be the original?
Did you buy it new or used?
1:20 is what it says for the White Mountain. That seems fast twist to me. Chap