Am I missing something?

[skychief12]

I've been thinking about having the Big Dot fitted (dovetailed) to my CW40. I started looking closer to their advertisements and have this question. How can the front sight be point of aim close and top of the dot over 25 yards?

In my world lowering the sights (top of the dot) causes the impact to be lower. Say Why??? Anyone know at what distance these sights are zeroed?

[JodyH]

Line of sight is a straight line.
Bullet trajectory is a curved line.
All sights are zeroed at two distances due to the bullet trajectory crossing line of sight twice.
Example: an AR15 zeroed at 50 yards will shoot 1.6" or so high at 100 yards and be zeroed again at 225 yards.
Big Dots are zeroed for around 5-10 yards.
This places the bullet trajectory above the sight line at 25-75 yards (which you compensate for by using the top of the dot as your aiming reference) and zeroed again at a distance well beyond what you can see/hit with a handgun.

[Tilos]

Your world is correct.
I have big dots and their "hold under" advise didn't work for me.

In fact, as Jocko has said, big dots are not target sights(pls don't post a link to THAT video, seen it).

This gun, before big dots, shot thumb size groups at 7 yards and fist size groups at 25yds.
After big dots, the 7 yd groups grew to fist size and at 25 yds it is difficult to keep them on a paper plate.

Since I bought a Kahr the big dot gun is now for gun games and the big dots have been replaced with FO front, plain Jane black rear.

Just sayin'
Tilos

[ripley16]

Anyone know at what distance these sights are zeroed?

According to the ad the sights are zeroed at 25 yards, where POA is the POI. You are able to get precise, aimed shots this way they claim, versus a faster shot at a close in target. The "close in" sight picture states the impact is "within the dot", which is close enough for success.

[JodyH]

Your world is correct.
I have big dots and their "hold under" advise didn't work for me.

This gun, before big dots, shot thumb size groups at 7 yards and fist size groups at 25yds.
After big dots, the 7 yd groups grew to fist size and at 25 yds it is difficult to keep them on a paper plate.

Just sayin'
Tilos

Your world defies physics?
Interesting.
In my world things like ballistics charts exist.
Study this AR15 ballistics/zero chart and you should be able to understand the way BD sights are zeroed.

http://www.box.net/shared/static/tppqdkapak.jpg

I can shoot one hole 5 shot groups at 10 yards with Big Dots.
3x5 head shots at 25 yards.
Poppers at 100 yards.
It's you not the sights.

[ripley16]

All sights are zeroed at two distances due to the bullet trajectory crossing line of sight twice.

This is not tue in all cases. Some guns have only one intersect point, pistols in particular. It depends on the design.

[jlottmc]

Oh we have the makings of a tiff here. Think I'll keep an eye on this, always like a good one. I'll bring the popcorn, and if need be will wade in when appropriate to keep things stirred up but sane.:popcorn::D

[JodyH]

This is not tue in all cases. Some guns have only one intersect point, pistols in particular. It depends on the design.
The only time there will not be two intersections is if the sights are designed to intersect the bullet trajectory exactly at the peak of its trajectory.
Big Dots are not designed that way, they are designed with two intersections.
btw: sights designed with one intersection will actually have one, two or zero intersections depending on environmental variations.

[Tilos]

JodyH:
Nice chart, do you have one for 9mm:confused:

When you super impose the big dot "bead" on a target at 7yds, how much, in inches, does the dot represent on the target?
How about 20yds?
50yds?
We are not talking cross hairs here.

Are we talking top of sight hold or center of "bead" hold?
Switching to one or the other depending on range?

Yep, just simple physics, and you are a much better shot than I.

I believe that wide, flat "V" of the rear sight (150 degrees+/-) is designed for quick acquisition and I'm glad to here they work for you at long ranges.
YMMV

Just sayin'
Tilos

[Bawanna]

I think it's just what a person is used to also. I used to be a straight up 6 oclock hold, put the point of impact on top of the front sight. The XS sights are designed to cover the point of impact (if all goes well) with the front dot.
When you want a little more precision you use the front dot like a post and put the desired point of impact on top of the dot.
You may have to do a little Daniel Boone Kentucky elevation in some cases but it works.

As for Basking and Robbins, to many options and I can never make up my mind. I'll take vanilla.

[ripley16]

The only time there will not be two intersections is if the sights are designed to intersect the bullet trajectory exactly at the peak of its trajectory.
Big Dots are not designed that way, they are designed with two intersections.


Can you provide a reference link to justify this statement please. Perhaps it is on the XS Sight site and I missed it or in their literature, but I've never seen it stated.

[Tilos]

Bawanna45cal:
Always the peace maker.
I have some big dots fresh off a glock, other than some blue loctite on the rear sight, they're like new.
PM me if it's something you can use.
Just sayin'
Tilos

[Bawanna]

Well I guess this throws my reputation as a rabble rouser right out the window huh?
Guess I better try to tick somebody off (besides the missus) before the day is out to get it back.
PM Sent.

[JodyH]

Can you provide a reference link to justify this statement please. Perhaps it is on the XS Sight site and I missed it or in their literature, but I've never seen it stated.
I get my info directly from Dave Biggers of XS sights.

That being said.
Think about it for a second.
Center of the dot is the impact point at 5 yards.
Top of the dot is impact point at 25 yards.
That means the bullet trajectory is rising in relation to the sight line at 5 yards.
What goes up must come down.
The bullet trajectory will intersect the center dot again at some point beyond 25 yards.
What that exact range is... you'd have to plug the numbers into a ballistics calculating program for your particular bullet, velocity and sight over bore distance.

[JodyH]

JodyH:
Nice chart, do you have one for 9mm:confused:

When you super impose the big dot "bead" on a target at 7yds, how much, in inches, does the dot represent on the target?
How about 20yds?
50yds?
We are not talking cross hairs here.

Just sayin'
Tilos
You can make your own chart for 9mm with any of the available ballistics calculators on the Internet.
Plug in the numbers for your gun/ammo combo and voila, instant sight in chart.

At 3 yards the Big Dot covers about 3/4", at 10 yards it covers approx. 1 3/4", I'm giving rough estimates based on how much of a 1" dot and how much of a 2" dot is exposed at those ranges.
At 20 and 50 yards you are at the point where you start "lollipopping" the front sight and it covers no more of the target than traditional notch/post sights.
We're not talking cross hairs but we are talking much more precision than 99% of the pistol shooters on the range are capable of.

Another trick with Big Dots is to use your binocular vision on targets smaller than the dot.
If you have an Aimpoint sight do this test as an example of binocular vision. Leave the front dust cover snapped over the front lens. Turn on the sight and aim in on a target with both eyes open.
Amazingly you can see the red dot superimposed over the target despite the front dust cover being closed.
You can do the exact same thing with Big Dots.
You will see the small target "through" the solid dot.

There are a LOT of misconceptions when it comes to using Big Dot sights.
They are not notch/post sights and you don't use them the same way.
They require a completely different approach to aiming and sight picture.
Once you learn how to use them they have some distinct advantages and some disadvantages, just like every other sighting method out there.

[Tilos]

JodyH:
Interesting analogy of Big Dots verses "notch/post" sights.
I understand how you could see it that way.
I'll have to consider all this, relative to my experience and profession.
Just sayin'
Tilos

[Bawanna]

So what your saying is when I'm shooting poppers at 150 yards with my PM45 with light cowboy loads I should use the lollipop method? Assuming of course that my normal point of aim is right on the money 1" groups at 85 yards?
You fella's buying any of this?

[JodyH]

So what your saying is when I'm shooting poppers at 150 yards with my PM45 with light cowboy loads I should use the lollipop method? Assuming of course that my normal point of aim is right on the money 1" groups at 85 yards?
You fella's buying any of this?
Are all of your other 3240 posts so insightful and informative?
If so, I really must search the archives.

[mr surveyor]

not to interrupt a good discussion, but.....

First, the instant a bullet leaves the muzzle it starts to drop (Newton had it right with his silly idea concerning gravity)

Second, firearms sights are constructed with sights that "elevate" the muzzle to a position that shoud cause the projectile to be on a certain elevation, at a certain distance, whether handguns or rifles.

Yes, the idea that a firearm will launch a projectile in a trajectory that crosses a horizontal plane at two points is true.... to the extent that the muzzle is elevated above the normal plane of gravity. (period) If the muzzle is perfectly horizontal, the bullet will drop proportionate to its mass and velocity, which is the reason that there are various height sights for both front and rear on handguns - depends on your preference for normal shooting distance and POA style.

Just in my opinion, the size of the sights has almost nothing to do with vertical trajectory, but the proportionate height of the front and rear sights (as well as the overall length of the sight radius) has everything to do with same. The size of the sights has more to do with the target acquisition (as in whether or not the precise point can be visually resolved).

just my 1/2 cents worth;)


surv

edit to add: I hope you guys don't stop this discussion or posting completely over this "disagreement". This kind of stuff is what makes gun boards worth visiting. I appreciate reading a good gun related debate.

[MikeyKahr]

:popcorn:

[mr surveyor]

Mikey

I don't know if this is a popcorn event or not, but it is a worthy topic for discussion (in my opinion). I hope all the participants will continue to contribute their opinions/knowledge. I hope it doesn't end up as a spectator event. Again, just my opinion here, there shouldn't be a "winner and loser" on this type discussion but just some facts we can all claim as true knowledge - then we are all winners.

surv;)

[skychief12]

This is good stuff! Smoke is rolling out of my ears.

Let me see if I got this.. mr surveyor says, based on the front and rear sight height and distance between the two a specific POI at some distance (straight line although angled) is established.

Next JodyH points out that based on information plugged into ballistic calculators, it is possible to determine where the bullet trajectory will intersect the sight line (mr surveyor) on both the ascending and descending trajectory path.

Next question, is there some way the above information can be used to optimism reloading parameters/components? Or can it? Let's assume paper punching to eliminate penetration. I understand things like barrel whip, machining tolerances, etc, still make part of reloading trial and error.

[Tilos]

All this can be fleshed out without getting into balistics, software, vectors, or formulas.
It has all been done many times before, with common sense examples and language everyone can understand, regardless of ones training or backround.
I just don't want to enter this "discussion" so soon after going through it on another forum.
I'll stay on the porch for this one.

Where's the popcorn??
Just sayin'
Tilos

[wyntrout]

Dang! If I'm in a gunfight, it's kind of a given that the other party is armed and desirous or perforating my pink/white body... AND the first item on my "To Do" list is avoiding that. To do so, I might be moving, ducking, rolling and otherwise be trying to find cover or make the BG's job a little harder. To that end, I might be interested in throwing a few wild shots in his general direction to make him think about something besides doing his darnedness to perforate my one and only personal body. I think taking the time to hold the gun correctly, take careful aim, adjust for target distance and motion, etc., MIGHT BE HAZARDOUS TO MY ****ing health. So pardon me if my shots don't fall into a 1" grouping at 7 yards or fist-sized at 15 yards. It's for this reason most of my practice and shooting involves quick shooting and my follow-up shots are accomplished by starting to preload the trigger (pulling it) as it approaches the desired aimpoint and firing as the point of aim passes through the desired point of impact.
I usually don't miss center of mass at 7 yards and can put most of my shots on the target at 15 yards... somewhere on the cardboard. :D I'm not a great shot with this, but I don't figure shooting slowly and deliberately at a paper target will help me that much in a real encounter where the BG is shooting at me!:eek: If you have the drop on someone and can do all of that... fine... more power to you. I really am impressed by the shooting ability of some of you guys... BUT, then we see and hear of actual gunfights where the police -- most can shoot well and are well-trained -- fire every round they have with little effect... like stopping or killing the bad guy. It happens, and you can't stand there and calmly shoot at the bad guy like the paper targets at a range without risking your life unnecessarily. JMHO.
Wynn:behindsofa::popcorn:

[jocko]

I love butter on my popcorn!!

[wyntrout]

I guess that kind of puts me in the spray-and-pray tactic group... hence the need to carry a reload.
Wynn:behindsofa::D:popcorn:

[Bawanna]

I suspect that many expert shots on paper targets and controlled environments (IE- no incoming rounds) would resort to spray and pray when they meet the elephant face to face.
One of those things that you'll never know until the elephant shows is face.
Many of the modern day training sytems in place now days can come very close and of course training in real world scenarios will help alot but still only very close.
I can't speak from experience, I've only seen elephants in zoo's and I had no desire to shoot them.

[mr surveyor]

all I was trying to point out is the fact that the bullet begins to descend at the instant it leaves the muzzle. The "bullet rise" is artificially built into the equation by having the muzzle slightly inclined by the construction and, or adjustment of the sights themselves.

Like Wyn said, in the event of a SD encounter precision shooting may not be a real issue. As far as I'm concerned, consistant paper plate accuracy from belly distance out to 10 yards ought to do it.

It IS rocket science, but I'm just a lowly land surveyor without the secret decoder ring. I just believe it's important that people understand the root of the mythical bullet rise phenomonon.

surv

[Bawanna]

Mr Surveyor, this is very unusual for me but I actually get what your saying. Your explanation is correct and the way that I've always understood trajectory. Not that I add any credibility to what is correct. The things you mention are compounded and more obvious when you talk about rifles and longer distance but the exact same stuff applies.
There are lots of factors that effect things also but the basic concept is exactly as you say.

It is rocket science which usually precludes me from the conversation but in this case its very old and well researched rocket science applied even way back on the ole muzzle stuffers. Been brought up a few times to say the least.

[OldLincoln]

Rocket Science?? I suspect the first cave man to throw a rock figured this one out pretty quickly.

[jlottmc]

:popcorn:

[Tilos]

My popcorn is getting stale, this thread is not very interesting since JodyH made it personal and stopped posting.
Just sayin'
Tilos

[Bawanna]

Ssshh, I think this is one of those glorious moments of peace while everyone reloads that someone mentioned, Jefferson maybe?

More salt, you won't notice the staleness.

[wyntrout]

Ya know, in a vacuum, if you drop a bullet from the same height as the barrel of a gun parallel to the ground and firing a bullet at the same time, both bullets would hit the ground at the same time. Forgetting of course, that the earth is a globe and not so flat. Maybe with the bullets, the vacuum is not necessary and you could use a feather and the fired bullet in a vacuum hitting the ground at the same time... maybe that was it. I'm getting confused and Wifey wants me to start supper... large beef tenderloins, mushrooms sauteed in butter and garlic, and some kind of green stuff, and of course copious amounts of aged grape juice... tonight from Gaul, er, France.:D
Dang... I missed another nap. Later.
Wynn:)

[Bawanna]

OK, everyone down to Wynns for supper. Beef! Its whats for dinner. You can have the old grapes and the unidentified green stuff, Beef, mushrooms, we're talking man food here.

[kahrseye]

All this technical stuff, which is far above my head, has made me hungry as well. Hope you have extra Wynn.....just sayin.

[wyntrout]

Dang. I just lost what I had typed... must be that old grape juice... 2006 Châteauneuf du Pape, Domaine de la Présidente, which is actually the cheap..., I mean least expensive of that "appellation"... ~$30 in Total Wine, the "Costco-like" wine and liquor warehouse. That's the most I'll spend and I don't do that often. I got a discount, or I wouldn't have bought that then.
The Angus beef tenderloin (Sam's Club) wasn't bad, either. We split about 22 ounces before trimming and I wound up with a bit more:D than my wife. Hers weighed 8.4 ounces after trimming... getting rid of the fat and chewy stuff.
Tomorrow night we'll have more mundane fair... baby back ribs... one of HER favorites. We just had mine.:) Whole petite green beans gave a bit of balance. And the mushrooms were pretty good, too. Lots of real butter on everything. I take meds for my high cholesterol... which reminds me.... There, I remembered to take my meds.:)
I wish that I could have shared with you guys, but you're kind of scattered about the country. I definitely thought about you while my snout was in the trough.:D
Dang! I coulda taken a picture... too late now.

Kahrseye, I love your signature phrase by Ben Franklin.... super! It's such a fitting metaphor, or analogy, especially for today's political climate.

Just got an email from Red Lobster and we got one from Longhorn Restaurant while we were eating.

Hmmm. "Am I missing something....?" I don't remember what the heck that was about, but you missed supper... that's dinner in the South. :D

Sorry for getting off topic <whatever it was>.

Wynn:yo:

[mr surveyor]

gravity?

no...maybe gravey?

[kahrseye]

Thanks Wynn, sounds like the perfect dinner to me... too bad I missed it. I know you told me before but what state do you claim as home?

[wyntrout]

Florida! I was born in Tampa, but spent a lot of time in Texas... used to call it my home state, but back in Florida since early '97.
Wynn:)