Any input? Head and neck shots only for night hunting.

Caliber?

Oops. 6MM, this hunting is to be done on small properties with cows and I want to limit penetration. Looking for just enough to get the job done but with little or no possible damage to the cows.

that is a varmint bullet. likely to blow up on the surface

I want them to blow up in the first 5-6 inches of neck or skull. I figure to get somewhat better performance than I get with the 22-250 I have been using.

The last hog I saw killed with a .243 was using a 55 grain Ballistic Tip -- head shot just like you specify and DRT. If you head-shoot them you can use any kind of bullet with the same result.

But be aware: The Ballistic Tip has a solid base of jacket material which causes it to penetrate surprisingly deep. On a smallish hog you could get full penetration and have a small hunk of lead and jacket continue on somewhere you don't want it. You might want to consider the 70 grain Sierra Blitzking, which shoots to the same POI with identical loads as the Nosler B.T. in my gun.

BTW: I've never had a bullet provide better accuracy than the 70 grain .243 B.Tip.

You will be pretty happy with that choice. As long as your piggies make the 50 pound mark or better you will be impressed with most vital shot locations and very quick death. It is very unlikely you will get pass through with any useable energy left.

I shot a bunch of wild goats with that bullet in a 243 in Australia. I never had a pass through, usually a frontal chest shot or behind the shoulder. I will say I was pleasantly surprised with how well it worked, all but a couple dropped like a brainshot.

I've taken mule deer with a .243 using 55g NBT humming along at 4050 FPS and the result was a flopper.

Distances was around 175 yards and the bullet did not pass through the animal. I did not find the bullet in the animal when cleaning it out and it was shot in the chest in front of the diaphragm. I did find a lot of pieces of this pink sponge like matter I think they call a lung.

Never shot a pig with any caliber so I would defer to those that have that experience.