This article originally appeared over at the First Strike sub-forum of M. Carter Brown. That thread can be found here. Check it out if your interest in the subject extends to the community’s reaction and inputs. I’ve broken it up here on the blog into a series since the different aspects of rifle scope design are so broad that I didnt feel comfortable adding them on to this post as they get written. Each one is really it’s own subject and deserves a more dedicated treatment.
I’ve just got a few more considerations to put out there.
Scope Tube Diameter. Probably about 30mm. I want to retain compatibility with after market scope ring accessories, like red dot mounts and levels and stuff, while giving myself as much interior working room as possible without aesthetically unbalancing the scope. 30mm strikes a good balance.
Hood. The design will use a pretty long hood on the front of the scope body. This protects the objective lens from anything but one-in-a-million direct paintball shots, minimizes stray light entering the system and reducing image quality, and it allows the end user to customize the total length of the scope to the gun it’s being used on.
Anti-Fog. For the anti-fogging properties, I’m kind of torn between classic nitrogen filling and deliberate environmental exposure. Nitrogen filling is industry standard and everyone expects it, but the nitrogen will eventually leak out the scope and degrade its ability to resist fogging. The alternative is to allow the free exchange of gas inside the scope (through protected vent holes) so that temps on each side of the glass will be equal – and thus not fog. Highly effective but potentially short term fog resistance and more complex machining/assembly vs less effective but infinite use fog resistance with simple machining and assembly…
In closing, I leave you with the interior comparison of an ACOG and a conventional variable zoom rifle scope:
What a difference.
The bottom scope is an unholy clusterfuck of objective, field, and relay lenses. They’re all necessary to produce a quality image and viewing experience in a variable zoom rifle scope. The top is elegant as can be. The front lens is an achromat to correct for color (which is a concern in short scopes like the ACOG), a roof prism to erect the image in a compact way, and what looks like a Barlow lens for the ocular – a simple lens design that extends eye relief. The ACOG cross section proves that world class combat optics and simple scopes go together like First Strikes and rifled barrels.
Also, I’ve updated Part 3 and 4 of this series with some of the semi-final design decisions. I say semi-final because they are finalized for the prototype but subject to change as needed after that. If you havent seen the updates yet be sure to check them out.