The only mods were that I rebedded the M70 when I got it, before I ever shot it. I scraped out the hot glue bedding and free floated the barrel. I use JB weld for bedding material. While I had it out of the stock, I adjusted the trigger to about 3#. The scope is an old Leupold Vari-x III 2.5-8X.
I worked up reloads using a method that involves finding the vibration nodes of the barrel. It made a difference in finding the sweet spot quickly. The method involves loading a series of shells, one round at each powder charge, varying the charge by .3 gr. from starting to max charge weight. Shoot them all in one group, noting as you shoot, where the bullets impact. You will typically start with shots scattering quite widely, but as you approach a node, the bullets will land on top of one another (for a few charge weights), and then scatter again. I found two distinct nodes with this rifle and 120 and 140 gr bullets. Then it's a matter of picking out the powder charge that coincides with the node. The results speak for themselves. It's a variation on shooting multiple 3 shot groups at varying powder charges - it just saves on bullets and powder.
Next time I will shoot some 5 shot groups, just to see that the node really is the node.
Tom