Re: 600 Yards with a 1911?
.45 ACP ammo with 150 f/s spread? That's pretty high. Most of my hardball equivalent loads run about 30 f/s spread.
Assuming a fairly tight velocity spread, the bullet will fall the same distance every time at any given distance. 600 yards is going to require some serious hold over, but it will be the same every time.
Bullseye type pistols are usually considered 'adequate' if they shoot groups no greater than six minutes of angle (3" at 50 yards). So at 600 yards, that's about 36 inches - oddly, the exact size of the black.
I have two 'hardball' target pistols, neither prepared - to the best of my knowledge - by Mr. Lippard. I've never shot either of them from a machine rest, but on a good day, I can run a score of 80 or so. I've hit full size silhouette targets with boring regularity at 100 yards when I was younger and shooting more often.
So I'll have to say this is possible. Which, for the tallybooks, is not an endorsement of the specially modified and precision built Lippard pistols.
I will also admit I've never fired a handgun at 600 yards. A couple of M14s, but not a handgun.