A hollow-point bullet is one that has a small hole in its front or tip end. The purpose is to flatten out or expand when entering a soft target to decrease penetration and destroy tissue. From my own experience at hunting small game, the .22 high-speed hollow point is a more reliable stopper than the 40-grain solid-point bullet.
Over the years I have taken hundreds of squirrels, several ground hogs, plus a few rabbits, foxes, skunks and a couple of ruffed grouse with a .22 rimfire rifle. Using 36 or 37-grain hollow-point ammunition, I get quick humane kill with body shots.
In the late 1970s, I thought I might try squirrel hunting using Winchester's .22 Wildcat ammunition. This high-speed round uses a 40-grain lead bullet that is graphite coated. I was hunting with a good squirrel dog on one particular day when he went after an old fox squirrel. I got my first shot off at this squirrel at about 50 feet. The squirrel ran out on a limb and jumped onto another limb of a dead locust tree as if it was not even hit. It stopped there, and I got off a second shot at about 75 feet. It then started up the tree and stopped again about 6 inches from a hole about 20 feet above the ground. I fired a third shot, and the squirrel slowly crawled into the hole leaving its tail sticking out.
I ended up going back to the house to get a crosscut saw. After about 45 minutes of hard manual sawing, the tree came crashing to the ground, and I was sweating from head to foot. The squirrel had not moved since it went into the hole. When I pulled it out and examined it, I realized that I had hit this large fox squirrel with all three shots. The exit holes were about the same diameter as the entry holes.
While walking back to the house, I thought, "Well, this is what I get for trying to transcend established methods." I have never hunted small game with .22 solid-point ammunition again.
When a hollow-point bullet strikes a target, the velocity pressure created at the front of the bullet forces the bullet to expand. This process is often referred to as mushrooming.
This squirrel season I have taken 16 squirrels with my favorite .22 rifle. When hit through the shoulders, the entry hole is the same diameter as the bullet, but the exit hole is sometimes as big around as a nickel.
Hollow-point bullets lose a large percentage of their energy on contact. They rarely ricochet off a hard object like a rock. This lessens the possibility of hitting anyone or anything else other than the target.
Today, the .22 Long Rifle High Velocity hollow point is often called "the queen of small game hunting loads" by most of the firearm writers. The advertised muzzle-velocity of the 36 or 37-grain hollow- point bullet is about 1,280 feet per second in a rifle with a 22-inch barrel. The velocity at 100 yards is 1,015 feet per second.
A telescope-mounted rifle sighted in for 50 yards will have a mid-range trajectory of less than 1 inch. This will allow humane kills on squirrels, rabbits, and small varmints at this range.
When accuracy is important, the hunters using a .22 rimfire need to test their rifle at a shooting range with a variety of ammunition. This will determine the particular firearm's preferences. The accuracy of different loads can vary greatly in the same gun regardless of the make, model or quality of the rifle.