OK, I've read numerous opinions that external adjustment scopes (ala Elcan) are bad for field use, but I don't remember reading exactly what problems such adjustments present in the field (and I'm not bright enough to figure it out on my own).

Can someone sum up the problems with ext adj scopes for me?

Thanks!

From what I've heard, it can get mud and dirt in it, or freeze in place

Historically, the first telescopic sights were on externally adjusted bases. Then I believe it was Zeiss that came up with the internally adjusted scope.

As for the problems of using an externally adjusted scope out in the field, any debris that could stop a weapon from firing could also not allow the adjustments to work properly. With that being said, one of the weak points of any scope is the fact that the parts inside of it move.

Imagine yourself in the front seat of a car driving down the highway at an incredibly fast speed and wearing a seat belt. Suddenly the car comes to an immediate halt, and even though you're wearing a seat belt, inertia keeps you moving forward except the belt will limit your movement and snap you back in the seat. That's what the internal parts of the scope go through each and every recoil cycle.

Target shooters used to remove anything to do with internal adjustments and fill the space around the erector tube with expoxy to hold it in place. They then would use the scope with an externally adjusted base. The less movement, the more consistency in shot placement, and consistency equals accuracy.

Like anything else mechanical, wear will occur and then you have degraded performance. And more importantly anything can fail for any number of reasons at any time.




ETA thanks to DevL I realize I never anserwed the question. No, there is nothing wrong or bad about an externally adjusted scope.

If you are talking about Elcan this is my understanding after asking a bunch of people with experience with them.

1. Old Elcans had some polymer parts for adjustment that would wear out.  This caused numerous problems with dirt wearing the scopes adjustment mechanism.

2. Next generation had all meatal construction.  Much better and probelms largely stopped but they had no lock so if the optic came out of adjustment there would be grime and sand that would wear the adjustment parts when you rezeroed.

3. Next they put adjustment locks on the unit so once you adjusted the unit if it had BDC marks in the reticle you never needed to adjust it again (for a short range optic that you dont dial in for range or windage often like he Elcan).  You lock the adjustments and dirt and grime wearing the moving parts became a non issue.  Sure they get dirty but if they dont move they dont wear.

This is all second hand info gelaned from a lot of people.  If someone can insert corrections please do as Id like the full story myself.