I got some steel HRT rings from Brownells, for a Leupold VXIII 6.5-20X. These are machined to such close specs that lapping isn't supposed to be necessary. (Well, assuming your 2 piece base is parallel...)
I put them on a Warne Maxima base set for a MRC 1999 (same hole spacing as Win M70) and, surprise, lapping tool dropped right it. Lapped it a little just for form, but I think the mfgr's claim is pretty good.
Still working on bedding the barreled action into the stock, but the scope was less work than I thought it was going to be.
I like the HRT's. They are rugged without being extremely heavy.