RE: UltraDot scopes..does point of impact change with dot size?

NRA Action Pistol with revolver

Still Winter up here and haven't been out to the range yet to experiment. Was wondering if anyone using one of the Ultradot MatchDot scopes noticed a change in the "zero" (point of contact) among the various dot sizes?

I'd like to use the large dot for 10 and 15 yard targets...and then the smaller dot for 50 yards targets.  

Maybe if I knew mechanically how the dot size changes i.e. are there 4 red dots (bulbs) inside the scope or are there 4 different size apertures that rotate to align/reflect from one stationary red light.

Thanks

You're asking two different questions:

1. Will the point of impact change between 10 and 50 yards? Most likely yes.
   
2. Will the point of impact change if I change my dot size at a given yard line? No.
   

Will the point of impact change if I change my dot size at a given yard line?



My experience is Yes.

I'm no expert nor do I know much about the red dot sight construction especially the short type. But in most red dot scopes the dot is reflected off the surface of a lens. To do it the lens must be tilted. In most cases the dot increases in diameter as intensity increases. I would think that with the angles involved the increase in dot size is not symmetrical in that the dot will increase in size more on the bottom, sides would be the same. The result would raise bullet impact. I would also think that it would be worse on the short scopes than the longer ones.

I actually tested 4 dot dot sizes and zero all with the same gun. Groups were different place with each dot size.

Jack H wrote:I actually tested 4 dot dot sizes and zero all with the same gun. Groups were different place with each dot size.

Thanks...that's my concern...sure would like to learn the actual mechanics used to increase/decrease dot size in the Ultradot units. Maybe I can just ask them?

OK From wikipedia:

The size of the dot generated by the LED is controlled by an aperture hole in front of it made from metal or coated glass.^[2]

Link: https://en.wikipedia.org/wiki/Red_dot_sight

Tried to open the footnote link to view the patent...but the patent link doesn't work. Was hoping to determine the mechanics of an adjustable aperture hole system.

One of the footnote links...good info:

http://www.bullseyepistol.com/dotsight.htm

My understanding "now" is that there is only one LED emitting the red light to the tilted lense. With an adjustable dot scope there is a revolving screen with various size holes that the LED emission passes through before reaching the lense.

If so, point of contact would be negligible.

Upper40 wrote:One of the footnote links...good info:

http://www.bullseyepistol.com/dotsight.htm

That is great info!

I was going to ask if this is equally true for Aimpoint, but I don't think any of my Aimpoint sights allow me to change the dot size.

Curious - why would anyone need/want to change their dot size from what they usually set it to?

mikemyers wrote:I was going to ask if this is equally true for Aimpoint, but I don't think any of my Aimpoint sights allow me to change the dot size.

Curious - why would anyone need/want to change their dot size from what they usually set it to?

 Related to Action Pistol in my case:

When shooting multiple targets at 10 yards with 3 and 4 second time limits the large dot is easier to locate. Then at 50 yards time limits increase and the smaller dot helps with more precision shot placement

Can you try using an intermediate size dot, and increasing the brightness for action shooting?
Some red dot sights show a larger area, which makes it easier to know where the dot is.

As a test, if you leave your sight set at some size for action shooting, and increase/decrease the dot size, shooting at the same distance, how much of a difference does it make?   Between 25 yards and 50 yards, I've read here that all sights need to be adjusted, due to the distance.

To my eyes, on any sight, increasing the brightness beyond a certain amount makes the dot appear larger.

Which sight are you using?  Based on past experience, my 30mm Ultradot is "easier" for rapid fire, compared to the 1" Ultradot, as it shows a larger area, making it easier to find the dot.  My Aimpoint sights, H-1 and H-2, always show a large area, and the  Aimpoint 9000 shows an even larger area (but is so heavy!).

Lastly, Ultradot recently introduced a new 1" sight with selectable dot sizes.  I'm not interested in it because it's heavier than the older 1" Ultradot, but you might want to try one and see how it works for you.

You obviously need another gun!

I'm getting confused.  You are asking about "NRA Action Pistol with revolver"


I assume these are the rules?  http://rulebooks.nra.org/documents/pdf/compete/RuleBooks/Action/act-book.pdf. 

From those rules:
The following firearm modifications are prohibited.

• Single action only firearms.
  
• Custom-shop firearms.
  
• Changes in the original factory sight configuration of the firearm, front adjustable sights.
  
• Peep, ghost, optical, electronic, Bo-Mar and Aristocrat type sights.
  

Apparently optical sights are not allowed?

I use several UltraDot 30mm with several “dots” and “dot within a dot” and the “crosshairs dot”. I use them on HP Pardini, Pardini 45ACP and Styer LP50. I use the smallest dot possible for the conditions. I have never noticed any change in POI to POA from 10M with air pistol to 35M with 45ACP…

I recently put one on a Ruger #3 rifle and played around with all the different “dots” and intensity levels. Unfortunately or maybe fortunately at 100M there wasn’t enough change to miss a 6” gong….
Just my results and experience YMMV….

I can say that the point of impact definitely changes relative to dot size with the Ultradot II. Confirmed on multiple occasions.