Forward slide-mounted optic?

[Jack Suber]

The further away from the pivot point (wrist) the higher the dot will rise and fall.

There's much more barrel rise than "rear-of-slide" size [rise?] on a non-comp gun. The dot will move more and more, the further it is from the back of the slide. Since your eyes are target focused on a dot-gun...

So, dots mounted on a frame mount over the front of the chamber (like a C-More on a frame mount) would seem to exhibit this same amount of additional dot movement, compared to the "rear sight" location.

So I'm curious... would you guys have the same opinion if we replaced the red-dot scope with a laser? Would you say the dot from a laser would have more rise depending on how far forward it was mounted (ie grip mounted vs guide-rod)? If yes, then why? If no, then why is a red-dot scope any different?

imo: In both cases the sight is always the same distance from the pivot point (on the target!). It's not like irons where you're looking at a point at some variable distance between you and the target. It seems that a dot from a laser would rise the same no matter where it's mounted since it's always pointing in line with the gun. I don't see a dot scope working any differently (ignoring parallax). Or after all this time do I not get how a dot scope works?

-rvb

Compare the movement of a rear sight during recoil to the front sight in relation to the target. That is what you would experience. The rear sight raise only slightly above the line of sight during recoil. the front rises much more. The same would happen with a dot if it were move further forward.

Years ago, someone toyed with the idea of mounting a JP Point type sight on the comp of an open gun. I shot one and did not like it. The glass got covered with garbage and it was hard to track the dot during recoil...even on a comped gun...

[Flexmoney]

So I'm curious...

It is...basically...on a lever, right? The fulcrum point (hand) doesn't move. So, you are talking about moving it to a further point on the lever.

And, the relationship we'd be concerned with would be that of the line of sight from the eye.

[rvb]

Too funny, flex. I just drew a similar picture, but reached a different conclusion. haha.

So.... with iron sights I totally agree the FS will appear to lift more in recoil the farther out it is. Never had a problem with that concept.

I also believe this same principal will apply to the scope body itself. This, along with other factors (eg the distance the scope is from the shooter will change the field of view) will change how the dot appears in relation to the scope body. But will not change how the dot appears in relation to the target.

My perception of how a dot-scope works is that where-ever the gun is pointing, so is the dot (negating parallax).... much like a laser except the light doesn't make it to the target and you can only see the dot through the glass.

For this reason, I just don't see how the dot can lift more based on where the scope is mounted, unless the gun recoils more..... and I don't believe the scope location can cause more recoil.

As the only dissenter, perhaps I'll just have to accept that there is "something" I don't get and go back to dryfiring.... I'm ok with that.

here is my sketch. the hollow dot shows what would have to happen for the dot to rise more off the line of sight.

-rvb

[TMC]

I've got an old Front Sight or Gun Games magazine around here with an article about a compensator with an Optima mount on it. Kinda weird but the theory was the dot would be in the same place as the front sight so the shooters focus is the same and because the sight was mounted to muzzle the accuracy would be increase because there is no slide/frame movement issues

[little_kahuna]

Here's a picture of a forward mounted red-dot on a CZ

That slide racker is sexy.

[nphd2000]

Look at your drawing. The "scope" closer to the tangent is 2" above the bottom line and the "scope" that is further forward is 4" off the line. I believe that's what the posters are trying to say. Meaning the dot will rise off the line of sight (bottom line) the further it is from the tangent.

[bdpaz]

As the only dissenter, perhaps I'll just have to accept that there is "something" I don't get and go back to dryfiring.... I'm ok with that.

I think that "something" is that you aren't trying to follow the dot/point of aim. You are right in that it points the same place (if it was truly parallax free, but that is a different discussion) but what you are trying to do is keep looking at the target and be aware of the dot. The farther forward it is the more it appears to lift off the original aiming plane in vertical inches even though it tilts at the same angle. There is also a limited field of view, and as the pivot point isn't your eyeball, you'll be looking into your optic from farther off center and you may lose the dot entirely.

Now, as to whether or not any of that makes enough difference in real life to be a problem, I haven't got a clue!

[rvb]

Look at your drawing. The "scope" closer to the tangent is 2" above the bottom line and the "scope" that is further forward is 4" off the line. I believe that's what the posters are trying to say. Meaning the dot will rise off the line of sight (bottom line) the further it is from the tangent.

But the dot is not "in" the scope. The dot is out "on" the target. This is why we keep a target focus w/ red dots.

Here's a cartoon version of what I imagine the difference would look like to the shooter at peak muzzle rise during recoil.....

the assumption is that all the guns recoil the same, to the same peak muzzle rise. same gun/ammo/shooter/etc.

the irons outlines show what you are saying, the FS farther out rises more. The scope shows what I imagine to be true, the dot rises the same on both, but the scope body/lens works much like the FS in the irons example.

Ignore geometry for a minute. The dot always points where the gun does, right? Why would the gun point somewhere else by moving the sight (the only way the dot can rise more if my last sentence is true)? This is what I've been asking since my first post on pg 1.

It's all just an academic exercise to me. Perhaps I've derailed the thread enough...

-rvb

Edited January 12, 2010 by rvb

[rvb]

You are right in that it points the same place ... The farther forward it is the more it appears to lift off the original aiming plane in vertical inches even though it tilts at the same angle.

so it [dot?] points to the same place, but appears to lift more?? My head hurts.

-rvb

[cas]

You're really over thinking this and from the wrong direction.

If you have a non mounted dot sight and something to simulate a slide you can prove them right in a matter of seconds. I did.

[bdpaz]

What would hurt if you were right would be your eye , because you would need the gun pressed against it so it pivoted there.

Try this one:

Once you are significantly off center on a red dot sight it isn't working as designed. A red dot sight is an optical device with parallax and field of view limitations and is not the same as a laser spot actually on the target.

[JeffWard]

So, dots mounted on a frame mount over the front of the chamber (like a C-More on a frame mount) would seem to exhibit this same amount of additional dot movement, compared to the "rear sight" location. I guess I'm confused why so many shooters put the dot out ahead of the chamber on 2011 guns in a similar, non-slide-mounted position, and they're perfectly fine with the additional dot movement stated above. My initial idea was to combine the location of a traditional frame mounted C-More, on an ultra-low slide mounted Jpoint, to bring the sight plane down as close to the bore line as possible, similar to iron sights.

Open guns just "flip" (barrel rise) MUCH less, due to the comp. A limited (non-comp) gun will suffer more barrel rise, so the dot will move more.

Jeff

[ohdsmith]

Here's a picture of a forward mounted red-dot on a CZ

PLEASE ADVISE ME OF THE MAKER OF THE BRIDGE FOR THE RED DOT SCOPE....THANKS OHDSMITH@AOL.COM

[ohdsmith]

Here's a picture of a forward mounted red-dot on a CZ

THAT is the ticket! Problem I see with a G22 frame vs. the CZ is drilling into polymer isn't really a solid solution to mount with screws. Maybe like a Carver mount, but much lighter weight (with no rear torque arm) and a super-low platform for a Jpoint in the same location would be a perfect solution.

PLEASE ADVISE ME OF THE MAKER OF THE MOUNT (BRIDGE) I NEED ONE... THANKS OHDSMITH@AOL.COM

[Got Boost?]

The further away from the pivot point (wrist) the higher the dot will rise and fall.

I have multiple open guns shooting the same ammo; one has more parallax then the others. The only noticeable difference that I can see between the two is that the one with more parallax has the C-More mounted a little further forward. They all measue to be the same height. Can some of you math wizards tell me if this may be the cause?

[mpolans]

Here's a picture of a forward mounted red-dot on a CZ

THAT is the ticket! Problem I see with a G22 frame vs. the CZ is drilling into polymer isn't really a solid solution to mount with screws. Maybe like a Carver mount, but much lighter weight (with no rear torque arm) and a super-low platform for a Jpoint in the same location would be a perfect solution.

PLEASE ADVISE ME OF THE MAKER OF THE MOUNT (BRIDGE) I NEED ONE... THANKS OHDSMITH@AOL.COM

That's a CZ factory part. You could try contacting cz custom and see if they can get one for you.

[gdboytyler]

Shooting with a dot means focus is on the target. Moving the dot 3 inches forward or back-wards will make very little difference in dot size or window size when using it at arms length such as in a pistol mounting...

Totally disagree.

Moving the red dot sight forward on the slide by 3" will make the window LOOK 15% SMALLER. I did the math to calculate the MOA (minute of angle) of the objective lens based on the position on the slide.

I had also done an empirical test with a CMore and a Leupold Deltapoint. The CMore has a 29mm lens. The Deltapoint has a 26mm (wide) x 18mm (high) lens. I mounted both sights at the same time on my Tactical Solutions .22lr kit that has a combo picattiny rail and dovetail sight. I mounted the CMore just forward of the ejection port and mounted the Deltapoint on the dovetail (about a 3" difference). With that configuration, the Deltapoint window looked wider, but still shorter than the CMore.

I also shot the TacSol with the Deltapoint mounted forward of the ejection port and with the dovetail mount. I shot ALOT BETTER with the Deltapoint mounted on the dovetail. On the TacSol, the picattiny rail/dove tail does NOT move with the rest of the slide.

After I confirmed that I liked the dovetail mount on the 22lr, I mounted it on the dovetail of my 38SC open gun and got good results. There have been plenty of reviews that say the slide-mounted Deltapoint and Trijicon RMR can handle thousands of rounds.

Edited May 11, 2012 by gdboytyler

[Griz]

As the only dissenter, perhaps I'll just have to accept that there is "something" I don't get and go back to dryfiring.... I'm ok with that.

You are the only one who gets it. Your laser analogy is 100% spot-on.

ETA: Everyone else is thinking about the glass.. That does move more, but we are not focused on the glass, we are focused on the dot/target. The dot will move exactly the same amount no matter where the glass is mounted. The only time it would be an issue mounted forward would be if muzzle rose so far that the dot moved off the glass.

Edited May 11, 2012 by Griz

[Xdmeister]

When shooting a dot gun you shouldnt really be focusing on the dot anyway so the location shouldnt matter

[eric nielsen]

When shooting a dot gun you shouldnt really be focusing on the dot anyway so the location shouldnt matter

http://www.brianenos.com/forums/index.php?showtopic=86559