Oehler Research · Ballistic Chronographs
Oehler Model 35BNC
Built for indoor ranges: connects directly to Model 57 infrared screens over BNC, so indoor lighting has no effect.
The outdoor Model 35P relies on sky-lit Skyscreens, which cannot work reliably in an enclosed range with no natural light. The Model 35BNC instead connects over BNC to Model 57 active infrared screens that carry their own light source, so the room can be bright or dim without affecting the trigger. It measures the average velocity between two screens: the first sits 5 or 10 ft from the muzzle and the second 10 or 20 ft beyond it. Add the optional middle screen and the unit records two velocities per shot for cross-checking. Output is a 2.25 in adding-machine tape printer for an immediate record. Power is 120V AC stepped down to 9V DC by a plug-in adapter. The design is simple and robust, which suits permanent use on a production line.
Overview
The Model 35BNC is the basic tool for indoor ballistic testing. It reports the average velocity between two screens: the first is placed 5 or 10 ft from the muzzle, clear of muzzle blast and flash, and the second 10 or 20 ft beyond it; distance divided by transit time gives the velocity. The same verification logic as the Model 35P's PROOF CHANNEL is available here: with the optional middle screen installed, the unit records two independent velocities per shot and the operator can see at once whether they agree. The sensors are Model 57 active infrared screens, with an infrared source across the top and several photodetectors in the base, so they do not depend on ambient light at all and run reliably in an enclosed range or at night. Output goes to a 2.25 in adding-machine tape printer whose consumables are easy to find; power is 120V AC stepped down to 9V DC by a plug-in adapter.
Key specifications
| Measurement | Average velocity between two screens |
|---|---|
| First screen | 5 or 10 ft from the muzzle |
| Second screen | 10 or 20 ft beyond the first |
| Optional middle screen | Gives two velocities per shot for cross-checking |
| Output | 2.25 in adding-machine tape printer |
| Power | 120V AC stepped down to 9V DC by a plug-in adapter |
| Sensor interface | BNC, direct connection to Model 57 infrared screens |
Features
Active infrared, independent of ambient light
Triggers reliably in enclosed ranges, at night, or under poor lighting.
Standard BNC interface
Connects straight to Model 57 screens: simple cabling with few points of failure.
Add a middle screen for two readings
Two independent velocities cross-check each other, so doubtful data shows up immediately.
Paper tape output
Standard 2.25 in adding-machine paper, easy to source, printed as you shoot.
Simple and durable
Suited to permanent, long-term use on a production line with little maintenance.
Configuration and applications
SENSORS · SCREENS
Model 57 active infrared screen
Infrared source at the top, several photodetectors in the base; a projectile crossing the reference plane produces a +12V pulse with a rise time of about 0.1 microsecond.
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