I'm the GM and manufacturing engineer of a small machine shop. Assuming there's enough available space for the laser, batts, and switching mechanism, I see no reason why I couldn't easily make a modified guide rod. I also have Solidworks 3D design software, so I could design it and verify the design and function digitally before cutting the first chip. The first problem is, given our overhead burden rate, unless someone ordered a bunch of them, they would be very expensive, as I'd have to devote time to CNC programming, setup, etc.
Having said all that, I hate to dampen hopes, but I have serious doubts that this would work. Even though the tiny "working" components of the laser appear to be small enough in diameter to fit in the available space below the barrel, you have to consider that there needs to be sufficient wall thickness between the inside diameter of the guide rod (which must be large enough to contain the laser mechanism and batts) and the guide rod outside diameter, to handle the loads exerted on the rod during firing. The fact the recoil spring is having to do so much work due to the high recoil forces relative to the low slide mass (as evidenced by the 200 round max spring life recommendation) tells me the guide rod must have high compressive, tensile, and yield strength and stress crack propagation resistance, all of which does not favor a small diameter, thin walled tube. So the remedy would be to increase the o.d. of the rod to increase wall thickness, which would then require a larger diameter spring of the correct spring resistance... and there's just not much room in the available space between the barrel and the frame to begin with.
Then, assuming that hurdle was conquered, one would have to figure out how and where to contain the batteries and how to design the rod assy so it easily disassembles to access the batteries to replace as needed... which means not only would the hollow rod have a thin wall, but it would have to be a multi-piece design in order to access the batt compartment, which implies using threads or other locking mechanism in an already thin wall. This introduces additional demands on available wall thickness and complexity of a part that by necessity has to be small.
Then, there's the aforementioned switching problem. The available space is already limited, and unlike the full sized pistols the Lasermax rods are designed for, there is no external levers or other access points on the exterior of the R9 to retrofit a switch, without involving milling or drilling a switch containment or access feature somewhere on the frame, where there's precious little real estate. Right off the top of my head, the only practical way of turning on the laser is by somehow designing the switch to activate when it contacts a stop as you rack the slide, and maybe turn off by itself with a timed electronic circuit. Or, maybe the switch could be contained somewhere in the mag well and activated via an external button on the right side grip panel.
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I just don't see how this could work without completely redesigning the gun to accommodate it. I certainly don't want to be pessimistic, as I'd love to have a guide rod laser for my R9 too. I'm simply thinking out loud based on what I've learned from my career in manufacturing. If anyone has any brilliant revelations on how to overcome these hurdles, I'm all ears and would certainly be willing to help.
