MilDot scope

[Franco2shoot]

My son brought up an interesting question concerning Scopes with MilDot reticules.

His theory is that scopes with variable zoom levels, lets say 4-9 power cannot use MilDot reticules since changing the power will distort the reticule.

He was looking for a good scope, but most were 6 to 12 power or 4 to 9, with various Reticules offered.

Since I don't really take any long shots and tend to set the scope at a mid range power and leave it there, I've never paid close attention to the reticules. I need some folks with Optical knowledge to shed some light on the subject.

Thanks

KKKKFL

 

[primalmu]

Since when does changing the zoom "distort" the reticle? Most mildot scopes I believe have second focal plane reticles and do not zoom in as you change the zoom. The reticle will stay in focus, but you will have to know different hold overs depending on the zoom setting. There are some mildots that zoom the reticle in as you change the scope's magnification.

 

[MCMXI]

Reticles in front focal plane (FFP) scopes maintain a constant ratio between target size and reticle size as the power is increased/decreased. Reticles in second focal plane (SFP) scopes do not.

 

[MCMXI]

This SWFA front focal, mil/mil scope is reasonably priced and seems to have good reviews.

http://swfa.com/SWFA-SS-3-9x42-Tactical-30mm-Riflescope-P50716.aspx

 

[TurtlePhish]

His theory is correct for second focal plane optics- the scope needs to be set to a certain specified level of magnification for the mil-dots to scale properly, otherwise calculations made with them will result in incorrect values.

My mil-dots are all fixed power, so I don't worry myself with that. The two variable scopes I have use more traditional hunting reticles.

 

[sscoyote]

A very important concept with mil-dot, or any multi-stadia second focal plane scopes for that matter is that subtension [angular measurements] changes are ~inversely proportional to magnification. This is the same concept that some ballistics programs use for their drop tables, such as Nikon's Spot-On program. This is actually a very fun concept to play with in the field in fact.

 

[mtrmn]

From what I've seen most variable mildot scopes that are NOT first focal plane are set up for the mildots to be correct at 10X.

 

[herkyguy]

For what it is worth I have a Leupold Mk-4 2.5-8X that is front focal plane, thus allowing all magnifications to work. It is fun to practice estimating ranges.

 

[HorseSoldier]

From what I've seen most variable mildot scopes that are NOT first focal plane are set up for the mildots to be correct at 10X.

FFP scopes tend to be more expensive. Second focal plane scopes are set up to function at a specific magnification (not necessarily 10x).