I like it when guys think outside of the box, and when that happens, the "It's Dangerous" crowd always quickly swarms. They serve a purpose and once in a while they have a point though. I wouldn't do this unless it was a closed base and/or a bonded bullet, and even then, would check the bore for debris for the first few shots.
My immediate question was "Why do you think drilling a hollow point will make it a varmint bullet?" Varmint bullets rely on thin jackets and other design features that make them fragile at the high speeds for which they are loaded. Those look like vintage "Silver Tips" which are a reasonably tough bullet designed for large game and will be travelling in the 2800 fps and lower range on impact. IMO, even with the HP, they'll just pass through a small critter much like a FMJ would.
As for accuracy, it's the condition of the base of the bullet, not the tip, that has the greatest effect on accuracy, They should still be as accurate as before the modification.
