I would try it with the 70 grain Speer Semi-Spitzer. Jackets are thin enough to allow obturation so with the right powder I am thinking it may upset to fill the rifling. The shorter length of the bullet in comparison to it's weight (because of it's somewhat blunt shape) will hopefully allow the bullet to stabilize in the 1-14 twist. The weight will cause better obturation because the the additional standing momentum as compared to a lighter bullet. For a bullet to obturate and still be accuract the nose of the bullet must set back evenly so it is not grosly off-sides, and the use of a blunt or flat nosed bullet is more likely to set back in the center then one that is longer.
I learned a lot about bullet use when I was working at Cast Performance as their ballistician and later as their CEO. So what I say next is gospel.
If the theory and the fact disagree, you will instantly know which is wrong. So with that said, try the 70 grain Speer and if all my ideas here, based in theory from my time in the lab...........if it doesn't work..........I was WRONG! But there is little to loose from trying.
The thing that makes you hair fall out is that the very next time you try it, in a supposedly identical rifle, (could be one made the next week) it may work perfectly.
