Re: Unertl bases
I have a copy of an old Unertl base chart. The only listing that is likely applicable on my Unertl chart is for the Remington 40 HB, which I think is the .22lr 40X.
The bases listed for this particular rifle are marked as R and A. According to the specs on the chart the R is .170 high with .600 hole spacing and the A is also .170 high with .562 hole spacing and a 3/8" bottom radius.
There were a couple of options for mounting bases on a Varmint 700 that you should consider as well. You can mount the rear base on the receiver bridge and the front base on the barrel, which is what the Unertl chart lists for the above bases. I think it is also possible to mount the rear base on the receiver ring with the front on the barrel, but this will place the mounts closer together and the scope adjustments will be different.
Be advised that the front mount (ring) on the typical Unertl or Lyman target scope is phisically shorter than the rear mount, and require some thought to base height and placement on the rifle accordingly. The dimensions of the R and the A base are both the same height but the rear base on the receiver bridge will be lower on the rifle vs. the front base on the barrel, this will account for the difference in the mounts on the scope tube.
I have seen the bases offered on ebay for the 700 a few times in the past, usually sell for $30 to $50 depending on who is bidding. The rear mount looks unique in that the locking cup is forward of both screw holes, so it appears offset and hangs over the open area of the action above the bolt when on the rifle.