point of aim vs point of impact

[xdf3]

23 hours ago, Blackstone45 said:

https://www.rifleshootermag.com/editorial/hitting-a-high-or-low-angle-shot/83768

basically, when you shoot on an incline, you have to work out the actual horizontal distance between you and your target, and hold for that.

Let's say you're shooting at a target 1000 metres away at a 20 degree incline. With a bit of trigonometry, you can work out that your horizontal distance to your target is 940 metres. 

So instead of holding for 1000 metres, you would hold for 940 metres. 

If you did hold for 1000 metres, your shot would go high as expected.

So the difference for a plate at a 20 degree incline would be almost equal to non-existant. Not even noticeable

[xdf3]

12 hours ago, rowdyb said:

zero at 50

Why would you zero at 50? So you hit no shoots / charlie etc... at lower distances? 4-5 inches is a big difference

[rowdyb]

I zero at 50 because that's the hardest shot I'll see and it actually gives you the least amount of hold over/under to deal with. It's the people who zero at 15 who have issues. As someone known as a points shooter rather than being speedy, there is absolutely not a 5" difference anywhere in my bullets path from 0 to 50 yard. The max ordinate is closer to 2" over that distance in my gun/hands.

 

With a zero at 50 where I aim, the bullet goes at any distance we shoot in competition.

[xdf3]

26 minutes ago, rowdyb said:

I zero at 50 because that's the hardest shot I'll see and it actually gives you the least amount of hold over/under to deal with. It's the people who zero at 15 who have issues. As someone known as a points shooter rather than being speedy, there is absolutely not a 5" difference anywhere in my bullets path from 0 to 50 yard. The max ordinate is closer to 2" over that distance in my gun/hands.

 

With a zero at 50 where I aim, the bullet goes at any distance we shoot in competition.

That's still an error, I don't see why not zeroing at 35 yards which would be enough to be perfectly ok at any distance. If I'm shooting a target covered with a no shoot, I feel totally safe (I zeroed at 27-28 yards) even when aiming right above the no shoot. With a 50 yard zero, it will be a no shoot 

 

It's not about gun/hands, it's about the cartridge. Unless you're using 115 grains at 1200+ FPS the difference should be more than just 2", especially at 5-10 yards

 

Anything from 22 to 35 yards is an optimal zero to me

[Yondering]

7 hours ago, xdf3 said:

That's still an error, I don't see why not zeroing at 35 yards which would be enough to be perfectly ok at any distance. If I'm shooting a target covered with a no shoot, I feel totally safe (I zeroed at 27-28 yards) even when aiming right above the no shoot. With a 50 yard zero, it will be a no shoot 

 

It's not about gun/hands, it's about the cartridge. Unless you're using 115 grains at 1200+ FPS the difference should be more than just 2", especially at 5-10 yards

 

 

No, rowdyb is right. Even with the slowest 147gr loads, a 50 yard zero puts the round slightly high at intermediate distances, not low, and the max offset is about 1" high between 20-35 yards. POI is not lower than POA except closer than 5 yards, where it's pretty much a point blank shot and only a couple tenths of an inch low at most, or farther than 50 yards. The numbers change slightly if we're using a red dot instead of irons, but not enough to change the point he's making.

 

With any load between the slowest 9mm minor and fastest 9mm major for iron sighted pistols, when using a 50 yard zero the POI should not deviate from POA by more than about 1.25". The big deviations you'll see are when using a close zero, like 10 yards. I think it's safe to say that very few of us are accurate enough shooting offhand for that ~1" offset to really matter.

 

 

Edited August 22, 2019 by Yondering

[xdf3]

6 minutes ago, Yondering said:

 

No, rowdyb is right. Even with the slowest 147gr loads, a 50 yard zero puts the round slightly high at intermediate distances, not low, and the max offset is about 1" high between 20-35 yards. POI is not lower than POA except closer than 5 yards, where it's pretty much a point blank shot and only a couple tenths of an inch low at most, or farther than 50 yards. The numbers change slightly if we're using a red dot instead of irons, but not enough to change the point he's making.

 

 

 

So why the opposite isn't true, like zero-ing at 15 yards? And why is it that different from charts? 

[Yondering]

With some loads, particularly the high speed stuff, a 50 yard zero does match a 15 yard zero pretty closely. With slower loads, the near zero changes to somewhere around 5 yards.

 

I'm not sure which charts you're referring to. The numbers I mentioned above are from ballistic charts, backed up by my own shooting to confirm. Maybe you're looking at drop tables, instead of trajectory tables that take sight/bore height into account? 

 

You also have to consider error in the zero, which is magnified when you zero at closer ranges. It's more accurate to zero (or at least confirm trajectory) at the longest distance you plan to shoot. If we "zero" at 10 yards but are actually off by 1", that error is magnified to 5" at 50 yards. If we zero at 50 yards and are off by 1", that error at 10 yards is only 0.2". 

 

The same applies for shooting a 5.56 AR15 with the common 36/300 yard zero - if we zero at 36 yards, any error is magnified nearly 10 times at 300 yards and our POI can be way off. If we zero at 300 yards, any error at that range will be very small at closer ranges. 

Edited August 22, 2019 by Yondering

[IHAVEGAS]

21 hours ago, rowdyb said:

I zero at 50 because that's the hardest shot I'll see and it actually gives you the least amount of hold over/under to deal with. It's the people who zero at 15 who have issues. As someone known as a points shooter rather than being speedy, there is absolutely not a 5" difference anywhere in my bullets path from 0 to 50 yard. The max ordinate is closer to 2" over that distance in my gun/hands.

 

With a zero at 50 where I aim, the bullet goes at any distance we shoot in competition.

 

There are a lot of free ballistics calculators on the internet if you do a web search, they are fun to play with. I zero at 15, because for my load and distance from muzzle to sight that is the first zero crossing of bullet and point of aim, the second zero crossing is somewhere around 35 yards (going from memory). I could zero at the second crossing but I am lazy  . The ballistics calculator, and some verification on the range, lets you pick the zero crossings you want for minimum error overall. 

 

After the zero is done I check at whatever I think max distance should be , for USPSA something like 50 yards. The check confirms my bullets fly straight more than anything, there have been issues (e.g., crimping too much on coated) where I have been throwing curve balls that didn't break until after the first close zero point. 

[xdf3]

9 minutes ago, IHAVEGAS said:

 

There are a lot of free ballistics calculators on the internet if you do a web search, they are fun to play with. I zero at 15, because for my load and distance from muzzle to sight that is the first zero crossing of bullet and point of aim, the second zero crossing is somewhere around 35 yards (going from memory). I could zero at the second crossing but I am lazy  . The ballistics calculator, and some verification on the range, lets you pick the zero crossings you want for minimum error overall. 

 

After the zero is done I check at whatever I think max distance should be , for USPSA something like 50 yards. The check confirms my bullets fly straight more than anything, there have been issues (e.g., crimping too much on coated) where I have been throwing curve balls that didn't break until after the first close zero point. 

There must be something wrong with options, the drop I see is much bigger than the one said by rowdyb and Yondering. I used this one for example:

 

http://gundata.org/ballistic-calculator/

 

I still can't understand how zero-ing at 50yards makes a so little change below 25 yards. How isn't it about 4" below at 5 yards?

[rowdyb]

55 minutes ago, xdf3 said:

How isn't it about 4" below at 5 yards?

because the distance between the top of your sight and the center of your barrel isn't 4". At 5 yards the barrel, sight and bullet can't physically be 4" apart so you aren't going to have that issue. and at close distances that's essentially all that's happening. i know this isn't totally true but imagine it this way. think of the distance between the top of your sight and the center of your barrel as the base of a triangle. this will remain constant. now draw the other sides of the triangle out to 15 yards and then again out to 50 yards. Which triangle is the thinnest/pointiest? The one drawn out to 50. In my experience zeroing at 50 gets me the least amount of change on any shot inside that distance. And I know exactly where I'll be on any hard/far target.

 

the classic diagram of a barrel pointed up, sights level and the bullet arcing out and crossing through a straight line (think the diagram explaining why zeroing your 5.56 AR at 50 yards also gets you close at 200 yards) doesn't come into play with pistol rounds and distance to near the extent as a rifle round.

 

if the difference between your poa/poi is 4" between a target at 5 yards and 30 yards you're doing something wrong when you pull the trigger, imho.

Edited August 23, 2019 by rowdyb

[xdf3]

30 minutes ago, rowdyb said:

because the distance between the top of your sight and the center of your barrel isn't 4". At 5 yards the barrel, sight and bullet can't physically be 4" apart so you aren't going to have that issue. and at close distances that's essentially all that's happening. i know this isn't totally true but imagine it this way. think of the distance between the top of your sight and the center of your barrel as the base of a triangle. this will remain constant. now draw the other sides of the triangle out to 15 yards and then again out to 50 yards. Which triangle is the thinnest/pointiest? The one drawn out to 50. In my experience zeroing at 50 gets me the least amount of change on any shot inside that distance. And I know exactly where I'll be on any hard/far target.

 

the classic diagram of a barrel pointed up, sights level and the bullet arcing out and crossing through a straight line (think the diagram explaining why zeroing your 5.56 AR at 50 yards also gets you close at 200 yards) doesn't come into play with pistol rounds and distance to near the extent as a rifle round.

 

if the difference between your poa/poi is 4" between a target at 5 yards and 30 yards you're doing something wrong when you pull the trigger, imho.

I'm looking at charts, I don't know what the real drop can be between 5 and 50 (I guess 5 and 30 would be more like 2.5 in that case")

 

It's really hard to notice the difference unless you have the distances, a rest, or anything that can remove human error. In my case, I think the trigger pull affects less than 10% of the error past 25 yards while aiming and wobble will be the rest

 

I used the calculator by choosing 124 grains, 9x19, 1050 FPS so a typical IPSC cartridge. I don't know what other options I should look for to read it properly

 

 

BTW : It sucks to have very few targets past 25 yards in most matches here (they are usually harder, with a lot of no shoots), and even harder to find ranges with longer distances. I know most top shooters zero from 18 to 42-43 yards 

Edited August 23, 2019 by xdf3

[IHAVEGAS]

31 minutes ago, rowdyb said:

 

if the difference between your poa/poi is 4" between a target at 5 yards and 30 yards you're doing something wrong when you pull the trigger, imho.

 

Which happens. People tend to change hold and place more emphasis on trigger control on the far shots.

[xdf3]

3 minutes ago, IHAVEGAS said:

 

Which happens. People tend to change hold and place more emphasis on trigger control on the far shots.

I actually do, but I prepared my gun so the error is minimal. When I double tap with little emphasis on trigger control, the error from that pull will be minimal. I actually lose more points due to how my gun returns after the first shot (which I'm working on).

 

Except for that human error, I was talking about the balistics only

[Yondering]

11 hours ago, xdf3 said:

I still can't understand how zero-ing at 50yards makes a so little change below 25 yards. How isn't it about 4" below at 5 yards?

 

Think about that for a minute. At zero yards (the muzzle) the bullet is low by the amount of the sight height over the bore; about 0.6". From there, how would a round go 4" low at  5 yards if it's back to zero at some further distance? It would have to drop and then rise again; that's not how it works. If that's what you're seeing on target, you're doing something different with trigger control; that's not a change in trajectory, that's a change in aim. 

 

If you're going to play with a ballistics calculator, you have to give it all the right inputs, otherwise the info is useless. Did you enter 0.6" for sight height?  

[xdf3]

22 hours ago, Yondering said:

 

Think about that for a minute. At zero yards (the muzzle) the bullet is low by the amount of the sight height over the bore; about 0.6". From there, how would a round go 4" low at  5 yards if it's back to zero at some further distance? It would have to drop and then rise again; that's not how it works. If that's what you're seeing on target, you're doing something different with trigger control; that's not a change in trajectory, that's a change in aim. 

 

If you're going to play with a ballistics calculator, you have to give it all the right inputs, otherwise the info is useless. Did you enter 0.6" for sight height?  

I'm not seeing that on target. However the issue was sight height. Except for that, a lot of people here whine about bullets going extremely high at further distances, like 3-4" at least at 50 yards. I think that's caused more by the zero + aim issue.

 

I'm still trying to imagine that. A 50 yard zero would make any aiming error between 0-50 more little while a 15 yard zero will make any error bigger? 

[shred]

Many factory guns come with 7-10 yard zeros.  Which puts the aim point for 25 into a 12-o-clock hold on an NRA bullseye target because the bullet is still going up.

 

[xdf3]

7 minutes ago, shred said:

Many factory guns come with 7-10 yard zeros.  Which puts the aim point for 25 into a 12-o-clock hold on an NRA bullseye target because the bullet is still going up.

 

Did you mean 6-o-clock hold? 

[IHAVEGAS]

1 hour ago, xdf3 said:

Did you mean 6-o-clock hold? 

220 , 221 , whatever it takes.

[xdf3]

On 8/22/2019 at 10:37 PM, Yondering said:

With some loads, particularly the high speed stuff, a 50 yard zero does match a 15 yard zero pretty closely. With slower loads, the near zero changes to somewhere around 5 yards.

 

I'm not sure which charts you're referring to. The numbers I mentioned above are from ballistic charts, backed up by my own shooting to confirm. Maybe you're looking at drop tables, instead of trajectory tables that take sight/bore height into account? 

 

You also have to consider error in the zero, which is magnified when you zero at closer ranges. It's more accurate to zero (or at least confirm trajectory) at the longest distance you plan to shoot. If we "zero" at 10 yards but are actually off by 1", that error is magnified to 5" at 50 yards. If we zero at 50 yards and are off by 1", that error at 10 yards is only 0.2". 

 

The same applies for shooting a 5.56 AR15 with the common 36/300 yard zero - if we zero at 36 yards, any error is magnified nearly 10 times at 300 yards and our POI can be way off. If we zero at 300 yards, any error at that range will be very small at closer ranges. 

About the error being magnified, I want to understand better. Let's say I have a group of 2" at 50 yards at the center of the target. That means my aiming might lead to an error of that group (2") at 50 yards so it will less at shorter distances.

 

What would the opposite mean? "If we "zero" at 10 yards but are actually off by 1", that error is magnified to 5" at 50 yards."

Can you explain that part? Do you mean an error done when you are setting up sights, so that there's an error (and there will always be) and any aiming error will lead to a bigger one? 

I can't imagine the point properly

[Blackstone45]

24 minutes ago, xdf3 said:

About the error being magnified, I want to understand better. Let's say I have a group of 2" at 50 yards at the center of the target. That means my aiming might lead to an error of that group (2") at 50 yards so it will less at shorter distances.

 

What would the opposite mean? "If we "zero" at 10 yards but are actually off by 1", that error is magnified to 5" at 50 yards."

Can you explain that part? Do you mean an error done when you are setting up sights, so that there's an error (and there will always be) and any aiming error will lead to a bigger one? 

I can't imagine the point properly

Yes, an error when setting up sights. Any error at close range is magnified the further out you go. If you miss the bullseye by 1" at 10yards, that will translate to 5" at 50 yards. A 1" error when zeroing is no different, because in practice, you are missing by 1" because of the bad zero.

[Yondering]

4 hours ago, xdf3 said:

About the error being magnified, I want to understand better. Let's say I have a group of 2" at 50 yards at the center of the target. That means my aiming might lead to an error of that group (2") at 50 yards so it will less at shorter distances.

 

What would the opposite mean? "If we "zero" at 10 yards but are actually off by 1", that error is magnified to 5" at 50 yards."

Can you explain that part? Do you mean an error done when you are setting up sights, so that there's an error (and there will always be) and any aiming error will lead to a bigger one? 

I can't imagine the point properly

 

I think Blackstone covered it. You have to think about the angles; any error in your zero is an angle offset away from poa, and the distance that angle traverses increases with target distance. 

 

This happens when the pistol sights are poorly zeroed at close range. Maybe the operator didn't shoot very many rounds, or maybe shot poorly that day so the true center of the group was hard to determine. Regardless, if the true center of the shot group (when zeroing the sights) was not on the bullseye when the operator considered the gun "zeroed", that error gets magnified at further distance. 

 

You've mentioned shots going 3"-4" high at 50 yards; with most iron sighted 9mm pistols and ammo, the only way for that to happen (other than shooter error) is for the sights to not be properly zeroed. There is no zero point between 5-50 yards that will cause your 9mm rounds to land 3"-4" high at 50 yards, IF the zero is actually zero. 

 

However, let's look at what really happens if you attempt to zero at 10 yards but don't get it perfectly zeroed: Maybe you only fired 5 rounds per group between sight adjustments, shooting offhand, and those final 5 rounds happened to land a little low in the pattern a 20-30 shot group would have made. You might conclude from that target that the gun is zeroed correctly, when it's really zeroed about 1" high at 10 yards. Now at 50 yards, the poi should be about 2" low, but because of that offset in the inital zero, you'd be hitting about 3" high. 

 

Does that make sense?

[shred]

On 8/25/2019 at 3:16 PM, xdf3 said:

Did you mean 6-o-clock hold? 

Yeah, my bad.  Because the bullet's still going up with a close zero you have to hold low at distance..

 

 

[xdf3]

12 hours ago, Yondering said:

 

I think Blackstone covered it. You have to think about the angles; any error in your zero is an angle offset away from poa, and the distance that angle traverses increases with target distance. 

 

This happens when the pistol sights are poorly zeroed at close range. Maybe the operator didn't shoot very many rounds, or maybe shot poorly that day so the true center of the group was hard to determine. Regardless, if the true center of the shot group (when zeroing the sights) was not on the bullseye when the operator considered the gun "zeroed", that error gets magnified at further distance. 

 

You've mentioned shots going 3"-4" high at 50 yards; with most iron sighted 9mm pistols and ammo, the only way for that to happen (other than shooter error) is for the sights to not be properly zeroed. There is no zero point between 5-50 yards that will cause your 9mm rounds to land 3"-4" high at 50 yards, IF the zero is actually zero. 

 

However, let's look at what really happens if you attempt to zero at 10 yards but don't get it perfectly zeroed: Maybe you only fired 5 rounds per group between sight adjustments, shooting offhand, and those final 5 rounds happened to land a little low in the pattern a 20-30 shot group would have made. You might conclude from that target that the gun is zeroed correctly, when it's really zeroed about 1" high at 10 yards. Now at 50 yards, the poi should be about 2" low, but because of that offset in the inital zero, you'd be hitting about 3" high. 

 

Does that make sense?

This is clear

 

As stated above I mentioned shots going high/low or whatever 'cause of the wrong input. I didn't have a chance to shoot so far. Lately I've found some ways

 

Some people told me they were shooting high or low so that could be the reason I guess

 

I'll have to check that too since I tried to zero my gun at 25 yards but I'm not good enough to make such a tiny group yet

[Blackstone45]

8 hours ago, xdf3 said:

This is clear

 

As stated above I mentioned shots going high/low or whatever 'cause of the wrong input. I didn't have a chance to shoot so far. Lately I've found some ways

 

Some people told me they were shooting high or low so that could be the reason I guess

 

I'll have to check that too since I tried to zero my gun at 25 yards but I'm not good enough to make such a tiny group yet

Try shooting off a rest for more stability if you're trying to sight. Just make sure you're resting your wrists on the rest, and not the gun itself as that will affect the point of impact.

[xdf3]

Just now, Blackstone45 said:

Try shooting off a rest for more stability if you're trying to sight. Just make sure you're resting your wrists on the rest, and not the gun itself as that will affect the point of impact.

Another shooter which tests gun for military purposes and similar stuff told me the same, recoil will affect point of impact BEFORE the bullet leaves the barrel.

 

I'll have to try it again soon