Is this something that just occured, or have you had this problem for some time?
To safely move the safety, without damaging it, this what you need to do.
Remove the bolt from the rifle and clamp the section of the cocking piece that makes contact with the sear in a vise with soft jaws, so it does not damage the surface.
Pull back on the bolt, against the firing pin spring, while moving the safety to middle position. If this doesn't work, it is likely either broke inside the shroud or extremely gummed up. Most likely you'll be able to move it to the middle position.
Once you do this, you can depress the sleeve lock and remove the shroud, firing pin, and cocking piece from the bolt body.
At this time, if you want to totally dissasemble the firing assembly, you'll need to do the following.
Inspect the safety lever to be sure that it doesn't appear to be broken.
Keep close watch on your fingers and move the safety to fire position. This will quickly move the firing pin forward.
Next, you can use the vise again to depress the firing pin spring and remove the two firing pin spring retainers from the firing pin.
I like to have a rag handy that is cradled in the vise jaws to capture the retainers and spring.
After you do this, it will allow you to remove all the internals and have a good look at the safety from the inside. If it's broke, it will need a replacement of course, but if not, see if you can move it freely. If you can't, then you should consult a gunsmith, since the problem is most likely the relief cut in the cocking piece, and or the relationship between the cocking piece and the sear that needs to be adjusted.
These are not things that a hobbiest should attempt, but rather someone who has some very good knowledge of the model 70 system.
Good luck with your project and keep us posted.
