Thread: Heym Rifles

Regulation refers to getting the two barrels to shoot to the same point of impact at a specified distance with a specified load.

Quoted from Wikipedia: - Double rifle - Wikipedia, the free encyclopedia

Regulation of the two barrels is the trial-and-error, time-consuming, painstaking adjustment of the two barrels (and powder charges) prior to permanently fitting the "rib" between the barrels. During regulation of the barrels, the two barrels are mated to the rifle's frame and butt-stock, but the permanent "rib" that goes between the two barrels is not yet installed. Instead, the rifle builder will braze a "temporary" metal wedge between the two muzzles, fire each barrel at a target at a specified distance, then note the point of impact of each projectile on the target, comparing where the projectile fired from the first barrel strikes in relationship to the projectile fired from the second barrel. If the points of impact for the two projectiles on the target are outside the rifle builder's specific parameters, further regulation is called for, with adjustments made to the powder charge and/or the rifle barrels themselves. If the barrels themselves require adjustment, the solder holding the metal wedge in place is heated—freeing up the metal wedge—then the metal wedge is carefully moved incrementally forward, backward, or replaced entirely with a different-sized metal wedge. Each time moving or replacing the metal wedge is called for, the rifle builder must heat the soft solder, move or replace the metal wedge, then solder and test-shoot all over again.
The additional trial-and-error shooting and barrel/powder-charge adjustments go on until the projectiles of both barrels finally strike the target within the builder's specified parameters. Once the builder deems the double rifle is properly "regulated," the metal "rib" is added between the barrels, permanently mating the barrels together. The builder will then specify the exact projectile weight and powder charge used to keep the barrels "in regulation," and this information will be stamped into the metal flats on the top of the frame, underneath the barrels. If, at some later point in time, the shooter of a double rifle chooses to use a bullet weight and/or powder charge that is different than what the firearm was originally regulated for, the firearm will most likely require re-regulation. During the barrel-regulation process, some double rifles will easily "fall into regulation," while others will require considerable time and effort to obtain proper regulation—which adds to the labor cost and overall expense of the firearm.
By their very design, the two barrels of the double rifle must be aligned very precisely (but this does not mean in parallel) in order for the projectiles to strike at the same point of impact, or nearly so, at a given distance - usually not more than 300 metres (980 ft), and often much less. The alignment of the barrels is done so that the two projectiles will actually converge at a specified distance, whatever is deemed best for the given caliber and expected range of the quarry. Regarding sights, many modern double rifles will accept mounts to fit a telescopic sight, but most double rifles, particularly those used for dangerous game, are fitted with open sights.