Many companies out there are offering what we refer to as "universal optic cuts" and do not require you to send in your optic with your slide to be fitted. As a result many of our customers have asked us why we require them to send their optic in with their slide at the time of machining. Let's try and shed some light on why we do what we do.
First, having a close tolerance fit between the optic to the slide means the forces generated during recoil are transferred to the optic body, not the mounting screws or locating lugs/bosses. Match fit optics ensure there is no room for the optic to shift or move on the slide essentially making it one with the slide. While locating/recoil bosses and screws may support the optic under some conditions/use cases, they alone will not stand up to pistol slide recoil or hard use. The original intent of the locating lugs were to aid in indexing the optic on non-reciprocating platforms (such as riding piggyback on an ACOG, or offset on a rifle). The lugs are perfectly adequate on a rifle or shotgun, or even on a pistol frame mount. In these cases the lugs provide some additional support to the mounting screws and help the optic return to zero when the optic is removed and remounted.
The life of an optic mounted directly to a slide is an entirely different story. The optic experiences a tremendous amount of force getting jolted forwards and backwards every time the slide cycles. Just look at why Trijicon had to make a Type 2 RMR (the original battery contacts would lose connection under recoil). If the optic has any room to move on the slide the it is more likely that the optic will come loose. I have personally witnessed PLENTY of optic mounting failures and almost ALL of them were due to sheared screw and optics that began shifting around in the pocket. When we match fit your optic to your slide it is fully supported by the slide. The screws only have to do what they are intended to do which is clamp the optic down.
One additional benefit of a match fit optic cut is that you will have a more precise return to zero if the optic is removed and re-installed (which many require you to do when you replace the battery). Most often we find that after removing the optic and reinstalling it, the optic zero has not shifted at all.
Match fitting each optic to each slide absolutely means it takes longer to machine. There is nothing quicker or easier about it. Ask yourself this. Why would we spend more time on fitting your optic (which we don't charge any extra for) if we didn't know it mattered? It's simple, we want your optic to be as securely mounted to your slide as possible. One day you might just have to subject your optic to what is considered as "hard use" and we don't want it shifting zero or breaking off your slide when you may need it most.
A common question we get is why don't manufactures match have match fit optics if they are truly superior? The short answer is that it is next to impossible for the manufacturer of either the optic or slides (or a manufacturer that does both) to implement this on a scale suitable for production. They would need to either: Manufacture both the optic and the slide while holding an extremely tight tolerance (within .0005" where most hold a .003" to .005"), or have the optic to be mounted at the time of machining and machine the slide to fit the optic which would be paired in production. Simply put, this would be next to impossible to implement on a scale suitable for mass production. Thats where shops like us step in. We provide what large manufactures cannot: the most solid and secure way to mount an optic to your slide.
Now, one of the down sides to a precision fit optic cut is that if you ever have to replace the optic, your replacement may be a bit over or undersized compared to your original. Here's the thing: we don’t believe that counting on a replacement optic fitting the existing optic cut is priority vs the quality of the original fit of an optic to a slide. This is why we caution our customers to buy quality optics especially if this is a weapon they use for defense or duty (because it minimizes the risk of a failure and need of a replacement). Loose fit optic pockets are a compromise. Precision match fit is not.
If for some reason you do have to replace the optic and it is larger than the pocket we can always refit the pocket and remove some material. If the replacement optic is smaller, well, then you end up with what others refer to as a "universal fit" (although still probably closer tolerance because it was sized to the original optic, not what the largest COULD be).
We strive to provide you with the most secure, precise fit optic cut possible so that the potential of failure is minimized on a gun that may one day be used to save your life or the lives of others around you. THAT is the primary reason we take such a hard line on this.
An example of the precision fit you can expect from us. No screws in the optic and still secure...