I’m not going to get into what is the ‘best’ load or bullet weight for bowling pin shooting, just a simple examination of the physics involved. Of course, the basic object of most pin shoots is to knock the pins off of the table in the shortest time possible…For most of us, that would mean one shot, one pin. It seems pretty simple, until you actually try it, as any rookie can attest. Bear with me as this isn’t pure textbook physics, nor are the terms used all scientifically correct, but the math is what’s important.
The basic deciding factor is the force of the bullet striking a bowling pin weighing approximately 3 pounds. It must transfer sufficient force to the pin to accelerate it and move it clear of the table. So, most shooters tend to consider the muzzle energy of the bullet, defined as ME = (m x v2) / K, where:
ME = muzzle energy in ft/lbs
m = bullet weight in grains
v = muzzle velocity in feet per second
K = constant based on acceleration and converting grains to pounds: (1 ft/lb divided by (32.163 ft.sec2 x7000) or, simplified, 450,435.
So, a 230-grain bullet traveling at 800 fps gives us:
(230 x 800 x 800) / 450435, or 326.8 ft/lbs of energy.
As many pin shooters can attest, .45 ACP is almost always perfect for the job. However, thinking in terms of muzzle energy, we know that even the small-by-comparison 9mm parabellum seems better. For example, where the above loading in .45 ACP yields 326.8 ft/lbs, a 115-grain bullet traveling at 1200 fps give us:
(115 x 1200 x 1200) / 450435 or 367.6 ft/lbs of muzzle energy.
Of course, the rookie decides the 9mm is obviously the way to go! Until he sees that a lot of times, the 9mm only knocks the pins over, instead of flinging them clear of the table as the ‘numbers’ indicate they should. Why?!?!?
Instead of bullets, let’s look at…What else? Bowling balls!
The average pro bowling ball weighs 16 pounds. The length of the bowling lane, from the foul line to the head pin, is 60 feet. On average, in pro bowling, the ball takes about two seconds to travel that 60 feet, and sends the pins flying…for the head pin, it gets knocked about 36 inches backward, good enough for any pin shoot, right? Well, the surprise comes when we crunch the numbers:
16 lbs x 7000 grains/lb = 112,000
60 ft / 2 sec = 30 ft/sec
So, plugging those numbers into the above equation gives us:
(112000 x 30 x 30) / 450435 = 223 ft/lbs of ‘muzzle energy’… Less than what the .45 ACP gives us. So how in the quack can it take out 10 bowling pins so decisively, with not nearly as much ‘muzzle energy’?
First, for muzzle energy to be a factor, we assume that ALL of the bullet’s energy is transferred to the target. If the bullet glances of the rounded surface of the pin, that won’t happen. The bullet would have to strike the pin perfectly straight on, which is a difficult accomplishment (especially when shooting 5 pins in 3 seconds or less!)
You can have a 110-grain bullet in a .357 magnum loading scream along at 1600 FPS, which would give you 625 ft/lbs of muzzle energy, eclipsing the .45 ACP, but it would probably punch right through the bowling pin, thereby not transferring all that energy to the pin.
Then, you have some plain weird stuff happen…It’s not uncommon to find slugs laying close to the pin tables, or have slugs ricochet back toward the firing line. Remember, at the bowling alley, the bowling ball has LESS ‘muzzle energy’ than most bullets at a pin shoot, and I’ve never seen the ball ricochet back towards the bowler. The bullet shouldn’t do it either, but it happens! The simple fact is that on paper, we can make things look very neat but in the real world, it’s not so simple.
So the REAL answer as to ‘why’ lies in momentum, not muzzle energy. We’re going to look at the bowling ball again. Where muzzle energy had a more complicated formula, momentum is simply a measure of the force applied to an object to move it and, as a result, the force that object transfers to its target. Instead of (m x v2) / K, momentum can be expressed simply as
m x v, where:
m = weight of the bullet in pounds, and
v = muzzle velocity in feet per second.
With the weight in grains instead of pounds, we merely divide by 7000, changing the expression to
((m x v) / 7000).
And, taking the above examples and calculating for momentum in pound-feet per second instead of muzzle energy in foot-pounds, we get:
Projectile Grain wt. velocity momentum
.45 ACP 230 800 26.3
Bowling ball 112000 30 480
357 Mag 110 1600 25.1
9mm 115 1200 19.7
Holy Discrepancy, Batman!!! No, that's not a typo. Not only can we finally see WHY the 9mm does not perform as well as the .45 ACP during pin shoots, but why a bowling ball can really fling the pins around even though it doesn’t have much ‘muzzle energy’!
The basic deciding factor is the force of the bullet striking a bowling pin weighing approximately 3 pounds. It must transfer sufficient force to the pin to accelerate it and move it clear of the table. So, most shooters tend to consider the muzzle energy of the bullet, defined as ME = (m x v2) / K, where:
ME = muzzle energy in ft/lbs
m = bullet weight in grains
v = muzzle velocity in feet per second
K = constant based on acceleration and converting grains to pounds: (1 ft/lb divided by (32.163 ft.sec2 x7000) or, simplified, 450,435.
So, a 230-grain bullet traveling at 800 fps gives us:
(230 x 800 x 800) / 450435, or 326.8 ft/lbs of energy.
As many pin shooters can attest, .45 ACP is almost always perfect for the job. However, thinking in terms of muzzle energy, we know that even the small-by-comparison 9mm parabellum seems better. For example, where the above loading in .45 ACP yields 326.8 ft/lbs, a 115-grain bullet traveling at 1200 fps give us:
(115 x 1200 x 1200) / 450435 or 367.6 ft/lbs of muzzle energy.
Of course, the rookie decides the 9mm is obviously the way to go! Until he sees that a lot of times, the 9mm only knocks the pins over, instead of flinging them clear of the table as the ‘numbers’ indicate they should. Why?!?!?
Instead of bullets, let’s look at…What else? Bowling balls!
The average pro bowling ball weighs 16 pounds. The length of the bowling lane, from the foul line to the head pin, is 60 feet. On average, in pro bowling, the ball takes about two seconds to travel that 60 feet, and sends the pins flying…for the head pin, it gets knocked about 36 inches backward, good enough for any pin shoot, right? Well, the surprise comes when we crunch the numbers:
16 lbs x 7000 grains/lb = 112,000
60 ft / 2 sec = 30 ft/sec
So, plugging those numbers into the above equation gives us:
(112000 x 30 x 30) / 450435 = 223 ft/lbs of ‘muzzle energy’… Less than what the .45 ACP gives us. So how in the quack can it take out 10 bowling pins so decisively, with not nearly as much ‘muzzle energy’?
First, for muzzle energy to be a factor, we assume that ALL of the bullet’s energy is transferred to the target. If the bullet glances of the rounded surface of the pin, that won’t happen. The bullet would have to strike the pin perfectly straight on, which is a difficult accomplishment (especially when shooting 5 pins in 3 seconds or less!)
You can have a 110-grain bullet in a .357 magnum loading scream along at 1600 FPS, which would give you 625 ft/lbs of muzzle energy, eclipsing the .45 ACP, but it would probably punch right through the bowling pin, thereby not transferring all that energy to the pin.
Then, you have some plain weird stuff happen…It’s not uncommon to find slugs laying close to the pin tables, or have slugs ricochet back toward the firing line. Remember, at the bowling alley, the bowling ball has LESS ‘muzzle energy’ than most bullets at a pin shoot, and I’ve never seen the ball ricochet back towards the bowler. The bullet shouldn’t do it either, but it happens! The simple fact is that on paper, we can make things look very neat but in the real world, it’s not so simple.
So the REAL answer as to ‘why’ lies in momentum, not muzzle energy. We’re going to look at the bowling ball again. Where muzzle energy had a more complicated formula, momentum is simply a measure of the force applied to an object to move it and, as a result, the force that object transfers to its target. Instead of (m x v2) / K, momentum can be expressed simply as
m x v, where:
m = weight of the bullet in pounds, and
v = muzzle velocity in feet per second.
With the weight in grains instead of pounds, we merely divide by 7000, changing the expression to
((m x v) / 7000).
And, taking the above examples and calculating for momentum in pound-feet per second instead of muzzle energy in foot-pounds, we get:
Projectile Grain wt. velocity momentum
.45 ACP 230 800 26.3
Bowling ball 112000 30 480
357 Mag 110 1600 25.1
9mm 115 1200 19.7
Holy Discrepancy, Batman!!! No, that's not a typo. Not only can we finally see WHY the 9mm does not perform as well as the .45 ACP during pin shoots, but why a bowling ball can really fling the pins around even though it doesn’t have much ‘muzzle energy’!
