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May
05

C-More Care and Feeding – Zero’ing and Adjustment

Arguably the most versatile and popular option on the market for IPSC/USPSA Open division sights, many folks have a love/hate relationship with their C-More Systems sight. With a little knowledge and experience, though, the C-More can be used for consistently good results.

This is the first in a series of articles on the Care and Feeding of a C-More Systems sight. These apply to Slide Ride and Serendipity style scopes equally.

The C-More was the first “tubeless” or “Heads Up Display” (HUD) style scope on the market for serious competition use. When it came on the market, the popular scopes were relatively heavy tube scope designs by Aimpoint and Tasco. Fast forward 18 or so years, and it’s rare to see anything but a C-More on an Open gun in USPSA/IPSC competition. There are certainly reasons why – the C-More is super light and eliminated the top-heavy feel that many Open guns had, and it worked out to be quite a bit less expensive than the popular tube scopes of the day. It’s still quite a bit less expensive than other viable options available today (the only other real option, the Aimpoint H-1, costs over twice as much and has fewer options, a smaller lens, and a small dot size).

The cost and form factor are not without some disadvantages, though. The C-More can suffer from parallax, and can have adjustment creep issues. The windage and elevation adjustments are quite coarse and have noticeable backlash, potentially making them frustrating to adjust. Finally, due to their lightweight, plastic construction, they can be broken by impact or very rough treatment. There are some other things to watch out for, too.

This series will look at each aspect of the scope, and talk about things to check during your maintenance cycle, and some tips about avoiding frustration with them.

Zero-ing and Adjustment

The C-More has a total of four screws involved in adjusting the scope. There’s a flat-head screw for windage, and one for elevation, an Allen head grub screw that locks the elevation adjustment, and an Allen head counter-sunk screw that locks the windage adjustment. While both adjustment screws are coarse, the elevation adjustment is particularly so. A small movement on the elevation screw results in a pretty large change in elevation. An eighth of a turn translates to something like a couple of inches at 50 yards! The windage adjustment isn’t quite that extreme, but it’s still coarse. Small movements are the key.

The elevation adjustment is marked clearly on both styles of scope (clockwise adjustment moves impact up), but on the more common Slide Ride version, the windage screw is not marked in any way, potentially making it confusing to adjust in the correct direction. Turning the adjustment screw clockwise will move the bullet impact to the right. So, “right” is “right”, if you will.

The elevation lock screw works very well, but on every C-More I’ve handled, the windage lock screw doesn’t really do much at all. See, instead of the end of the screw pressing against the adjustment screw, holding it in place, the angle on the counter sunk screw head presses against a matching angle on the windage adjustment screw. This just doesn’t work as well. It provides some friction, and can help hold the windage screw in place, but it won’t stop the windage screw from being adjusted, and it won’t stop the scope from having what I call “Wandering Windage” (more on that later). So, basically, I don’t bother messing with the windage adjustment screw. I make sure it’s firm, and leave it. If you overtighten the windage lock screw, you can strip it or crack the scope (it’s just threaded into the plastic of the scope body), and the allen head on this screw strips easily, and since it doesn’t really do much, you might as well not press your luck with it. Plus, because you’re putting tension on the scope body, there’s a possibility that you’re warping the scope slightly, and potentially affecting zero as you change the tension on that screw from adjustment to adjustment.

Take a good look at a C-More scope – see how the lens assembly sits on a hinge? Notice that the elevation adjustment basically compresses and releases this hinge to change the angle on the lens relative to the diode. That adjustment mechanism is pretty straight forward. Windage is done a bit differently, though. There’s a metal block that the elevation screw attaches to – this whole block is moved left and right on a pin by the windage adjustment screw. The means the whole lens assembly is shifted left and right, which changes the tension on the hinges. This means that as you adjust the windage, you also are adjusting the elevation. If you don’t realize that, you’re on the fast track to a rage quit! The elevation screw can theoretically change the windage adjustment, but it doesn’t seem to in practice.

Update: Here’s an image demonstrating that phenomenon – the scope is level to the camera, here, and the scope’s windage is adjusted all the way to the right (which moves the lens all the way to the left). You can see the near side of the lens platform is higher up than the far side. That vertical change is what results in the change in elevation…

Here’s my strategy for zero-ing a C-More. I typically zero my gun at 25 yards, but I’ll do a gross adjustment at a closer distance if I’m dealing with a new scope. If you choose to zero at a longer distance, get it close to correct on closer target. I start with the windage (because the windage could change the elevation adjustment you just made, if you do elevation first). If I’m doing the gross adjustment step, I leave it just a bit shy of perfect. This is because I’m going to fine tune my zero at a longer distance, and I don’t want to deal with the backlash issue, if I can avoid it (it’s not fatal, but it can add to the time I spend zero’ing). Remember to use good trigger control, and follow the steps I outlined for shooting groups with a red dot sight – you want to make sure that the only thing that’s changing is the adjustment of the scope. Get the windage where you like it, turning the windage adjustment screw a bit at a time without bothering the windage lock screw. Then, unlock the elevation adjustment, and adjust the elevation screw a bit. Then re-lock the elevation screw before proceeding – do this every time you adjust the elevation screw. You want to make sure that tension is close to the same on each adjustment, and that it doesn’t wander from shot to shot as you zero. Again, move slowly to try to avoid having to deal with backlash, and leave some room to move if you’re making a gross initial adjustment.

I recommend shooting more than one shot per adjustment – I work in three shot groups to insure that the gun is consistently hitting where I think it is. Occasionally, you’ll find that an adjustment doesn’t seem to “take” at all, or doesn’t “take” until you fire a shot, causing you to shoot a nice two shot group with a flyer. If you fire one shot, and then adjust based on that, you may find yourself chasing the scope all over the place. If you can’t seem to get a group, double check that all the scope mount screws are tight (including the two screws that mount the scope to the scope mount, if you’re using a Slide Ride scope on a mount), and check that the lens is tight in the scope. If none of those things are a problem, make sure it’s not you – have another shooter give it a try.

With some experience, you’ll get a feel for how much adjustment will change things on the target, and you’ll find a flow that works for you. I double check zero every time I shoot, and especially after travel on an airplane. If the bag takes an extremely hard impact (like, say, from baggage handlers tossing it around), it can change the zero on the scope unexpectedly.

You may also wish to use a silver or white colored marker or paint pen to make a small mark on the scope body to indicate where the adjustment screw is positioned. You can do the same for elevation. This will allow you to visually see if either screw is moving on it’s own accord. The marks are easily removed later with a solvent.

About the author

DaveRe

USPSA Grand Master, NRA Instructor, http://re-gun.com/about/

Permanent link to this article: http://re-gun.com/2011/05/c-more-care-and-feeding-zeroing-and-adjustment/

1 comment

5 pings

  1. David Crook says:

    Just bought my first C-More (on a 90 degree mount on an STI) after using PDP5 Coke cans and Oko sights – this is great! Understanding the system will really help me to get the most out of the system. Thanks heaps!

    David

  1. DR Performance says:

    C-More Care and Feeding part 1 – zero'ing! http://bit.ly/lWBVTw

  2. xre says:

    RT @drperformance: C-More Care and Feeding part 1 – zero'ing! http://bit.ly/lWBVTw

  3. crab_fishing says:

    RT @drperformance: C-More Care and Feeding part 1 – zero'ing! http://bit.ly/lWBVTw

  4. C-More Care and Feeding – Lenses, Diodes, and Mounts, Oh My! | Re-Gun says:

    [...] is the second post on the Care and Feeding of the C-More Sight red dot scope. If you missed the first post in the series, you might want to refer back to it for some initial comments and background. If you’re clear [...]

  5. C-More Care and Feeding – Fixing Wandering Windage | Re-Gun says:

    [...] is the 3rd and last article of the C-More Care and Feeding series. You might also like the first article on adjusting and zero’ing the scope, and the second article on the lens, diode, and [...]

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