Only have 6-7 yards shooting distance in my basement

[pgfaini]

I can't understand the difference. The sight alignment and the primary hold are both angles of error. And both of them are multiplied by the distance to the target. Of course the sight alignment is more critical, the distance being a foot or less (distance from front to rear sight), while the primary hold is almost three feet (distance from rotator cuff to front sight). But shouldn't the error should be equally proportional based upon the distance to the target?

If an "invisible" B-11 target was placed concentrically at 50 ft. between the shooter and his 50yd. B-19 target, and the shooter fired a 9.0, wouldn't it just touch the 9 ring on both targets?

I find this an interesting subject, because I'm fortunate enough to live in a rural area and am able to train at home. I've always shot FP at 50yds. and 50M, but since Wolf Creek has been lost, all my matches have been indoor, at 50ft. (Newberry, SC and at the Citadel). I've set up a 50ft. range, and I too, find it more difficult at 50ft. than 50yds., although logic would lead me to believe I should get a benefit from the larger (3-1) (relative to the scoring rings), bullet diameter. This is untrue, as my invisible target scenerio should prove. As the bullet passes through both targets, it would just touch the 9 ring on both targets.

Paul

[AAlex]

If an "invisible" B-11 target was placed concentrically at 50 ft. between the shooter and his 50yd. B-19 target, and the shooter fired a 9.0, wouldn't it just touch the 9 ring on both targets?

That is only true when you have no parallel error. Imagine if you have a camera inside the barrel that looks at your invisible target setup. If the barrel is moved off-axis (parallel error), then if you look from inside the barrel the targets will no longer appear concentric, and you cannot hit 9.0 on both targets with the same shot.

However, I'm going to retract my comment about triggering errors reducing nonlinearly on reduced distances - that was a momentary lapse of reason.

[Nicole Hamilton]

I can't understand the difference. The sight alignment and the primary hold are both angles of error. And both of them are multiplied by the distance to the target.

Actually, no. I concede it's counter-intuitive at first, but parallel error is NOT multiplied by the distance.

As long as your sights are perfectly aligned (no angular error) and all you're doing is moving the gun up or down, left or right, whatever distance you move at the firing position is exactly same distance you'll displace the shot in your target. It's like firing down a tube and moving both ends up/down, left/right, always the same amount. As long as you don't change the angle of the tube, a 1/4" change on the target takes a 1/4" change in your hand.

This why sight alignment (front + rear) is SO much more important than sight picture (sight alignment + bull).

[ColinC]

I may be missing the point but I think that there is no way that a bullet would strike the same spot on targets at different distances.
Suppose you fixed your pistol in a vice (I think US spelling is 'vise') and could shine a laser beam through the barrel. Place a target at 50m with the beam shining dead centre X ring. Place other scaled down targets along the way at 25m, 10m or wherever with the beam again being dead centre X-ring.
The moment you fire a bullet it starts to fall because of gravity. It might hit the x ring of a target a few metres from the barrel but will be lower at 50m.
Okay, I have put my neck out to be chopped off by the scientists out there.

[pgfaini]

AAlex and Nicole,
This would be true if it WERE parrallel error. But it isn't. You're facing the target pointing the gun at it. Any deviation from a 10.9 hold is an angular error, measurable in degrees, minutes, and seconds, whether caused by sight alignment or arm movement. If it were a triangle, looking down from above, your eye to target line and the target face would be two sides, and the shoulder to target line the hypotenuse. This is basic trigonometry.

IF you stepped two inches to the right, and fired through the "invisible" target to the center of the 9 ring on the 50yd. target,(parallel error) you would be somwhere in the 3 ring on the B-40 target, true, but when you stepped to the right, the targets were no longer concentric with your line of aim, which caused the thrown shot on the B-40 target.

ColinC, We're not talking exterior ballistcs here, but point of aim VS. angular error at differing distances.

This has become a very interesting thread!

Paul

[Nicole Hamilton]

This would be true if it WERE parrallel error. But it isn't. You're facing the target pointing the gun at it. Any deviation from a 10.9 hold is an angular error, measurable in degrees, minutes, and seconds, whether caused by sight alignment or arm movement.

That's true, if all you were concerned about was the "which way is the gun pointed" question. But for the shooter, who's trying get 10s, it's more interesting to look at it in terms of the sight picture he's looking at. Both points of view describe the same thing, but in different coordinate systems, analogous to the way we all learned to translate from rectangular to polar coordinates in HS geometry.

If we choose to view it from the shooter's perspective, sight alignment corresponds purely to angular error and sight picture is only parallel error. In that context, the "shooting down a tube" metaphor may help you visualize what's going on.

[pgfaini]

Yes Nicole, But your shooting down the tube metaphor, displaces the concentricity of the two targets, causing the greater error on the nearer, smaller target. There is no parallel error when shooting at a single target, it's all angular. If you move the tube parallel to its original position, the correct line to the target center is from either end, and the other end is off angularly

Paul

[Nicole Hamilton]

Yes Nicole, But your shooting down the tube metaphor, displaces the concentricity of the two targets, causing the greater error on the nearer, smaller target.

I'm not sure I understand your point. If the centers of both targets are at the same height and directly in front of the shooting position, the rings on both targets will be concentric about the same axis. So I don't know what you mean when you say this "displaces the concentricity of the two targets."

If what you mean is that the same parallel error translates into more rings on the near target than on the far target, I agree. In fact, that was the point I was making in commenting on the discussion we've had at my club about why shooting FP at 50' seemed more difficult than at 25 or 50 yards.

[pgfaini]

Moving the gun (tube) parallel in any direction causes the targets to no longer be both directly in front of the shooting position (concentric), and pointing the gun directly at the center of either target will cause an error on the other. With regard to vectors, the front-rear sight relationship is a radius, as is the front sight-eye relationship. They both move in an arc. The sine varying with the length of the radius, sight alignment is more sensative with regard to angular error, and so, bullet impact. I don't know how to make my explanation any clearer.

Paul

[Nicole Hamilton]

Okay, now I understand your point: You're thinking about the literal case of having two targets, shooting through the first, into the second.

We're talking past each other. I wasn't trying to address that. (I've never seen anyone line up two targets like that so as to care what would happen. :) But you're right, in that case, if you move the gun off the axis running through the centers of the two targets, then aim at the bull in the first target, it will be off-center on the second. Simple geometry.

What I was talking about was something different, speculating that parallel error (wobble in the sight picture, not the sight alignment) might be more of a problem if the target is closer.

[pgfaini]

Nicole, Of course I was only using the concentric targets as a method of illustrating that angular error is equal in both targets as long as their dimensions correspond to the distances at which they are used, and can't understand why I find the shorter distances more problematical.
I still don't accept the hypothesis that sight picture wobble is parallel error. These movements are in fact arcs, the angle of error increasing with the shortness of the radius. If I'm standing and pointing a pistol at a target, how can I creat parallel error without sight misallignment?
To me, the only way a parallel error is created, is if I swing my arm to the right, and correct the aim by cocking my wrist to the left, bringing the line of fire, parallel to the line of sight, the shot striking the target, about the same distance to the right, as my arm was swung. Could we subconsciously do this (correct by wrist movement) in an attempt to save a shot we should have aborted?

The only reason variations in sight alignment give greater angular error, for a given distance moved, is because of the short radius. The error you call "parallel", sight picture wobble, is just an angular error with a longer radius, because the arm is moving in an arc, not parallel to the line of sight.
Perhaps, although technicaly incorrect, parallel error is the common term for sight picture wobble, and Im just showing my ignorance in not knowing this particular piece of jargon. If this is the case, I apologize for beating a dead horse.

Paul

[Nicole Hamilton]

The error you call "parallel", sight picture wobble, is just an angular error with a longer radius, because the arm is moving in an arc, not parallel to the line of sight.

Now we're back to the point that the two descriptions are equivalent but stated relative to differing coordinate systems. In the coordinate system which distinguishes between sight alignment and sight picture, parallel error is just that: It's parallel, not angular, not with any radius.

[pgfaini]

Nicole, see my edited post, by the time I'd finished it, you'd already posted your reply.
Paul

[pgfaini]

Nicole, Just as my head hit the pillow(it's 1:20am here), I realized that any error caused by torso sway, would be parallel error. Can't believe I actually got up and posted this. Like I said, a very interesting thread. Good Night.

Paul

[Fred Mannis]

Nicole,
The biggest problem I notice at the shorter distance is that my wobble takes up a larger area of the target, which translate to a lower score.

Having initiated this, I'm sorry I was out all day and had to miss a great discussion.

Personally, I sense three types of aiming error - sight alignment, angular errors associated with movement of my arm at the shoulder joint, and sway of my body. Only the latter is parallel error. For me, the wobble is mainly the continuous random motion of my body. Having spent some time with a RIKA, I know that my random sway (wobble) is generally inside the 8 ring and on good days is inside the 9 ring. Angular errors - sight alignment and arm movement - are more like quantum jumps, ie larger irregular motions which put the shot out into the 7 ring or worse. These angular errors are often associated with errors in shot release and/or mental focus.

[Dragon 2]

Great conversation all.

Two points I would like to make based on how target geometry was explained to me.

Base assumption (until some can document this).
The Black on a target is optically set to be equal to the ten ring at 0.0 meters(yards) [basically, at the muzzle]. The range is not a factor except where convention and rules dictate.

1) it is possible to scale a target infinitely from 0.0 meters out to whatever range your pistol can shoot. The guiding factor is that the black on the target must be equal to the 10 ring at 0.0 meters. The calcualtion is a simple mathmatical relationship. Diameter of "black" , 10,9,8,7,6,5,4,3,2,1 rings at 10 meters are equal to X/(whatever rangeyo set) the equation will look soemthing like diameter 10 ring/10m=X/5m. Example solution ((diameter 10 ring(mm))*5m)/10m=Xmm.

2) The conversation above is mixing the factors of line of site and bullet/pellet trajectory. If you really want to get into the nitty gritty; spin rate, projectile wobble, and drift are also factors. An extremely precise barrel will place precisely similar rounds/pellets very precisely. With most competition pistols this is demonstrated by the proof target that holds 5 pellets or 5 bullets in a group roughly the diameter of a single shot.

Since the target diamters expand linearly from the muzzle in a cone; any movement of the muzzle from a fixed point relative to teh apex of the cone will change the point of aim on the target identically regardless of range. Sight alignment is key at any range because this is the mechanical device that determines point of aim along a fixed (but adjustable) line of sight.

If you were to demonstrate this priciple using laser beams in a vacuum you would see that point of impact for a perfectly straight line at any range would be identical. Projectiles are subject all kinds of external factors including, wind, drag, air pressure, muzzle velocity, weight, air density, and temperature (of air, barrel, air charge, and projectile).

A practical demonstration of the cone descirption is not possible using a projectile. You can get close with a very flat trajectory but nothing mecahnical moving any distance over the face of the earth will travel in a straight line. The greater the distance the greater the error due to all the external influences on the projectile.

Bottom line: Its all in your head once you adjust zero for the range you are shooting. By zeroing the pistol a shooter is setting an intersection of two trajectories. One is the line of sight and, for all practicle purposes, is straight as far as the eye can see. The other is the projectile. Depending on the pistol, ammunition, and range the arcing trajectory of the bullet is either climbing to meet the line of sight or falling back down to meet the line of sight at the point of aim on the target (your set range). We'll just ignore spin velocity, drift, and angle of fall at point of impact.

I had a harder time going from short to long range because I always believed those external influences had more opportunity to affect my projectile.

Love the conversation. Good shooting,
Phil

[IPshooter]

I have argued this point before and believe I am on solid ground. The reason I don't buy the parallel error story is because a pistol shooter's shoulder is a pivoting point with a relatively well defined terminating rotational end point. It's a ball-and-socket joint (albeit held together with muscles and ligaments with some cartilage thrown in) so the arm pivots within the shoulder joint.

Because it is this type of joint, true parallel error simply cannot occur. The only way that could happen is if the entire arm was dislocated out of the shoulder so the arm could move squared up to the target (along with the sights). You could do it, but it would hurt like hell and it wouldn't be long before that shoulder joint would be sheer junk.

Stan

[Nicole Hamilton]

The reason I don't buy the parallel error story is because a pistol shooter's shoulder is a pivoting point with a relatively well defined terminating rotational end point.

Stan, I think you may misunderstand what people mean by parallel error. They're not disagreeing with you about how people's arms work. All they're saying is that if you snapshot the sight picture at the instant the gun fires, you can analyze that sight picture to distinguish (even if somewhat artificially) between angular error and parallel error.

The reason this is important is because a lot of shooters, especially beginning shooters, don't realize that parallel error (poorly lining up the front sight with the target) isn't nearly as serious as angular error (poorly lining up the front and rear sights.) It's pretty hard to do something well if you don't know what the success factors are. The message behind separating parallel from angular error is that it's WAY more important to concentrate on sight alignment than sight picture.

It seems quite possible that you're a sufficiently advanced shooter you just take this for granted, but I can promise you that new shooters do not. In fact, even after you tell them, a lot of them won't believe you. They're sure that can't be right.

[IPshooter]

All they're saying is that if you snapshot the sight picture at the instant the gun fires, you can analyze that sight picture to distinguish (even if somewhat artificially) between angular error and parallel error.

The message behind separating parallel from angular error is that it's WAY more important to concentrate on sight alignment than sight picture.

Nicole,

Regarding the first paragraph, I don't think that's what they *are* saying. How many times have you heard someone explain hold like this?

"Walk up to the target, put your front sight up almost touching the paper, and if you can hold your front sight wobble within the 10 ring, then you have a 10 ring hold."

That's a load of bull. Anyone who's taken high school geometry can disprove that statement.

I don't dispute your second paragraph at all. There's no doubt that sight alignment errors generally produce wider shots than hold errors. But even that depends on the individual shooter. It all depends on how good is your hold, how good is your control of the sights, how good is your trigger control, how good is your follow through, is your mind right, and were those eggs cooked thoroughly... ;-)

Stan

[Nicole Hamilton]

Regarding the first paragraph, I don't think that's what they *are* saying. How many times have you heard someone explain hold like this?

"Walk up to the target, put your front sight up almost touching the paper, and if you can hold your front sight wobble within the 10 ring, then you have a 10 ring hold."

You and I must be talking to different people. I've never heard that, except maybe from some anonymous "guest" here on TT spouting claims he shoots AP 590 after 3 weeks. People I know in the real world say things like I said, that you can analyze a sight picture as angular and parallel error and that angular error is more serious and that's about it. That "shooting down a pipe" metaphor is, for example, one that our best shooter routinely mentions in his monthly pistol clinics when he explains angular and parallel error in just the way I tried.