As part of another project, I had occasion to do some deliberate contemplation and comparison of the Troy Folding Battle Sight (FBS) to the Midwest Industries Emergency Rear Sight (ERS). The two are being weighed for adoption as a standard issue BUIS unit by some folks using Aimpoint and Eotech RDS units. These sights were chosen due to their design features, commonality with existing systems, and pricing. The former representing a folder at a premium price of $130-150, the latter representing a quality folder at a more moderate price ($80-100). The goal, to contemplate the relative differences between the two, and what might be characteristic of others priced within those ranges.
These excerpts are part of a larger work. Posted here for those engaged in similar pursuits.
FBS, mounted at T1, Colt LE6920. This sight mounts to the receiver and is retained by a rail engagement bar clamped via a cross-bolt screw. The screw head is recessed. The rail is engaged along the full length of the sight base on the right side, and ~1/3 of the length on the left. The cross bolt is adjusted with a common household flathead screwdriver or field expedient of same from the right side. The windage adjustment knob is recessed. No elevation adjustment. Dual sight aperture, with small and large on the same plane. Low profile. The sight is raised to position without activation of a control, and is retained in place by positive locking mechanism. Released by a push button mounted on the left side.
ERS, mounted at T1, Colt LE6920. This sight mounts to the receiver and is retained by a rail engagement bar clamped via a cross-bolt screw. The rail is engaged along the full length of the sight base on the left and right side. The cross bolt is adjusted with a hex head wrench from the left side, and the screw head protrudes from it. There is no elevation adjustment. Windage adjustment is made through a conventional A2-type windage adjustment knob protruding from right side. Dual sight apertures, with same plane option available. Relatively low profile. Raised to position without activation of a control, and is retained in place by positive locking mechanism. Released by a push button on the left side.
The upright ERS is a standard A2-type configuration and a seamless functional and near-seamless form transition from conventional -A2 sights. The upright FBS differs from the A2-type in form, and operation of the windage control, but not essential function. The FBS is much akin to the A1-type. The apertures of both sights are manipulated in like fashion. Both sights deploy to the upright position, and are retracted therefrom, in like fashion.
Training of the end user for both systems will differ little from training on the existing fixed A2-type sight, primarily for deployment and retraction of the sight. The incorporation of same-plane apertures may be of note to those teaching aperture transitions.
Same-frame views, FBS top, ERS bottom.
Rear view, ERS (L), FBS (R). Differences in machining and tolerance are more apparent here.
Bottom view, FBS (L), ERS (R)
Screws, ERS (L), FBS (R). The MI screw is smaller in diameter than the Troy, longer OAL, and of longer threaded length, consistent with footprint.
Screw/Rail Gap interface, ERS (L-T2), FBS (R-T1). When placed within rail gaps, the smaller diameter of the MI screw is more apparent, and a visible gap between the screw and rail side wall is visible, as well as the rail address. The Troy screw is in nearly full contact with the rails on either side.
Movement of the ERS, mounted. Due to the screw diameters, the Troy mount demonstrates virtually no movement when placed loose on the rail and requires less torque to remain in position than the MI. The MI mount demonstrates the following visible movement when installed with slight tension on the screw, and requires a greater amount of torque to remain in position. Specific torque values were not quantified.
The effect of this movement on POI will be imperceptible to minimal at shorter ranges, increasing with distance.
Some cross bolt mounting systems such as these may produce yielding of the screw, especially with repeated removal and reinstallation. The small diameter, threaded length, and greater torque for mounting of the ERS would seemingly render it comparatively more susceptible to same, subject to further testing. User should monitor torque values, perceived, torqued, or observed via witness mark, for differential applications with each reinstallation.
As always, making witness marks on parts with motion is indicated, as is applying thread-locker to pertinent fasteners.
When deploying the ERS, ensure the correct sized tool is included with support gear.
The ERS unit is now deployed alongside the existing FBS units for field evaluation. Further reports to follow.
The ERS is available for ~$95 retail, and the FBS for ~$140. Both appear to be priced appropriately, and represent a good value for the end-user at those price points.
























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