The most likely reason we zero at 100 yards is that's the way we've always done it, but does that make it the best range to zero? I say NO, here's why.
The first reason: wind drift
You may not realize it, but I do a LOT of test shooting - powders, bullets, rifles, etc. When I shoot, I don't want to have to make wind calls and would shoot on windless days if that were an option - it's not. So to minimize the wind impact, I typically do testing at 50 yards.
Let's take an example. I want to measure the accuracy potential of my Ruger American Ranch gen 2 in 5.56 with a 77 gr MK bullet. So, I'll be shooting groups - 10, 3 shot groups to be exact. Wind affects the bullet significantly less at 50 yards than 100 yards. That might make you think, "Won't the wind drift simply be twice as much at 100 as it is at 50 yards?" Well, no, that's not right! Check out this plot of wind drift due to a 5 mph cross wind.
![Image]()
Hmmm, that turned out a bit small, but as you can see, the wind drift is NOT linear with range. And, it shouldn't be. Remember the further the bullet travels, the slower it gets. As it slows the wind has more time to push the bullet.
The numbers on the graph are almost too small to read, so here's the wind drift numbers for 50, 100, and 200 yards,
![Image]()
Range is pretty clear. The drift line is how much in inches a 5 mph crosswind will move the bullet at the specified range.
It's the factor line that's interesting, so I'll clarify a bit. Going from 50 yds to 100 yds is a doubling, or 2x for range. However, the effect of wind, as shown in the table by 100/50, is a factor of 4.2 - a bit over 4x!
Then, 50 yds to 200 yds is a range factor of 4, or 4x, but what's the wind effect from 50 to 200 yds? It's 17.8! This means the effect of wind at 200 yards is 17.8 times greater than the 50 yard drift!
Understand here that this is for a Sierra 77 gr MK bullet with a measured BC of 0.169 (i.e. not the box BC) at a measured average muzzle velocity of 2480 fps.
Different weight bullets with different BCs and different muzzle velocities will be different than the above results. But this still illustrates that wind drift is not linear. Just to support that, here's the same table based on a 140 gr 6.5 Creedmoor (G7 BC = 0.286) with a muzzle velocity of 2710 fps.
![Image]()
While the actual wind drift numbers are quite different than the 77 gr SMK, the quadrupling (4x) effect with range is quite close. In fact, almost precisely 4x per 2x in range.
OK, so that's one reason I zero and do most of my testing at 50 yards - it minimizes wind drift significantly!
Reason 2: target definition
I wanted to use a 15x scope. At 50 yards the definition of the POA is twice what it would be at 100 yards. To be almost equivalent at 100 yards, I'd need a scope twice as strong, i.e. 30x.
Reason 3: seeing hits
I'm shooting .22 caliber bullets. They can be hard to see and much harder at 100 yards than 50 yards. At 100 yards I have to use a spotting scope; at 50 yards my 15x scope is adequate.
Reason 4: Here's a biggy!
You get a better trajectory (path) with a 50 yard zero! Here's a plot of the same bullet, with the same BC, with the same muzzle velocity, but one zeroed at 50 yards (green plot) and the other zeroed at 100 yards (Blue plot).
Again this pic didn't fit well so it's small but I'll do some explaining.
![Image]()
Let's say we're zeroed at the classic 100 yard range and we see a 4" (2 MOA) target at 200 yards we want to try to hit. What if we hold dead center? Based on the 100 yard zero, where would our bullet land at 200 yards? Since we're holding dead center, our bullet can't drop more than 2" (2" from center to bottom of target). But at 200 yards the bullet drops 4.14 inches lower than the POA. We'd miss bad! Even if we held at the top edge of the 4" target, we'd still miss!
Same thing but a 50 yard zero. We'll hit below center by 1.66 inches at 200 yards. Since the target is 4 inches and we're holding dead center, our bullet will hit the 4" target!
This is actually the purpose of point blank range (PBR). PBR has come to mean very close range, but that's not the only meaning. Rifles can be sighted in to maximize a hit WITHOUT doing hold overs! Just aim dead center and pull the trigger. PBR relies on the fact that a bullet has an arc path. So it starts out below zero, moves through zero, then begins to drop below zero.
The idea is to find the range to zero that maximizes the range which you can shoot with a center hold and get a hit - WITHOUT hold over. But that's really another thread. Let me know if you'd like to see that.
The first reason: wind drift
You may not realize it, but I do a LOT of test shooting - powders, bullets, rifles, etc. When I shoot, I don't want to have to make wind calls and would shoot on windless days if that were an option - it's not. So to minimize the wind impact, I typically do testing at 50 yards.
Let's take an example. I want to measure the accuracy potential of my Ruger American Ranch gen 2 in 5.56 with a 77 gr MK bullet. So, I'll be shooting groups - 10, 3 shot groups to be exact. Wind affects the bullet significantly less at 50 yards than 100 yards. That might make you think, "Won't the wind drift simply be twice as much at 100 as it is at 50 yards?" Well, no, that's not right! Check out this plot of wind drift due to a 5 mph cross wind.
Hmmm, that turned out a bit small, but as you can see, the wind drift is NOT linear with range. And, it shouldn't be. Remember the further the bullet travels, the slower it gets. As it slows the wind has more time to push the bullet.
The numbers on the graph are almost too small to read, so here's the wind drift numbers for 50, 100, and 200 yards,
Range is pretty clear. The drift line is how much in inches a 5 mph crosswind will move the bullet at the specified range.
It's the factor line that's interesting, so I'll clarify a bit. Going from 50 yds to 100 yds is a doubling, or 2x for range. However, the effect of wind, as shown in the table by 100/50, is a factor of 4.2 - a bit over 4x!
Then, 50 yds to 200 yds is a range factor of 4, or 4x, but what's the wind effect from 50 to 200 yds? It's 17.8! This means the effect of wind at 200 yards is 17.8 times greater than the 50 yard drift!
Understand here that this is for a Sierra 77 gr MK bullet with a measured BC of 0.169 (i.e. not the box BC) at a measured average muzzle velocity of 2480 fps.
Different weight bullets with different BCs and different muzzle velocities will be different than the above results. But this still illustrates that wind drift is not linear. Just to support that, here's the same table based on a 140 gr 6.5 Creedmoor (G7 BC = 0.286) with a muzzle velocity of 2710 fps.
While the actual wind drift numbers are quite different than the 77 gr SMK, the quadrupling (4x) effect with range is quite close. In fact, almost precisely 4x per 2x in range.
OK, so that's one reason I zero and do most of my testing at 50 yards - it minimizes wind drift significantly!
Reason 2: target definition
I wanted to use a 15x scope. At 50 yards the definition of the POA is twice what it would be at 100 yards. To be almost equivalent at 100 yards, I'd need a scope twice as strong, i.e. 30x.
Reason 3: seeing hits
I'm shooting .22 caliber bullets. They can be hard to see and much harder at 100 yards than 50 yards. At 100 yards I have to use a spotting scope; at 50 yards my 15x scope is adequate.
Reason 4: Here's a biggy!
You get a better trajectory (path) with a 50 yard zero! Here's a plot of the same bullet, with the same BC, with the same muzzle velocity, but one zeroed at 50 yards (green plot) and the other zeroed at 100 yards (Blue plot).
Again this pic didn't fit well so it's small but I'll do some explaining.
Let's say we're zeroed at the classic 100 yard range and we see a 4" (2 MOA) target at 200 yards we want to try to hit. What if we hold dead center? Based on the 100 yard zero, where would our bullet land at 200 yards? Since we're holding dead center, our bullet can't drop more than 2" (2" from center to bottom of target). But at 200 yards the bullet drops 4.14 inches lower than the POA. We'd miss bad! Even if we held at the top edge of the 4" target, we'd still miss!
Same thing but a 50 yard zero. We'll hit below center by 1.66 inches at 200 yards. Since the target is 4 inches and we're holding dead center, our bullet will hit the 4" target!
This is actually the purpose of point blank range (PBR). PBR has come to mean very close range, but that's not the only meaning. Rifles can be sighted in to maximize a hit WITHOUT doing hold overs! Just aim dead center and pull the trigger. PBR relies on the fact that a bullet has an arc path. So it starts out below zero, moves through zero, then begins to drop below zero.
The idea is to find the range to zero that maximizes the range which you can shoot with a center hold and get a hit - WITHOUT hold over. But that's really another thread. Let me know if you'd like to see that.
