regulating shot pattern of doubles

[saltydog452]

Prior to cnc machining, computers, lasers, exotic cutting tools, etc., how were double barrel smoothbores of years ago regulated to print both barrels to point of aim at a given distance? Trial and error?

Brand name shotguns such as Parker, Lefever, A. Fox, L.C. Smith, etc., have a fairly high purchase price. Does this mean that they are/were significantly better at putting meat on the table? I can only assume that they were more consistent with both barrels putting the shot charge in the desired location. Is this a reasonable assumption?

I understand that todays entry level competition doubles do not necessarily print to the same point despite the considerable advantage of more up to date manufacturing methods.

I would appreciate your thoughts as to how the manufactures of the early to mid 1900s aligned both barrels to the same point.

thanks,

salty.

 

[mete]

That was one of the reasons for high costs of double shotguns and rifles .You have to do it by trial and error .Rifles were regulated for one load only and have to be fairly precise. Shotguns are not quote as difficult.

 

[JohnBT]

Solder, shoot, unsolder, resolder, shoot, unsolder, resolder, shoot, etc. JBT

From Abbreviations at www.griffinhowe.com

114. Regulation of Double Rifles - If the two barrels of a double-barrel shotgun shot 3" apart at 25 yards, not many people would notice because the pattern from each barrel, spreading two feet across at that range, would largely overlap. If, on the other hand, the two barrels of a double rifle shot 3" apart at 25 yards, it would probably shoot 6" apart at 50 yards and 12" apart at 100 yards, limiting its utility.

One cannot build a double rifle, using sophisticated mass-production machinery with barrels perfectly parallel and expect both barrels to shoot to a common point of impact. While the bullet is travelling down the right barrel (of a side-by-side double rifle) the rifle will be pushed up and to the right, throwing the bullet up and to the right when it exits the muzzle. While the bullet is travelling down the left barrel, the rifle will be pushed up and to the left, throwing the bullet up and to the left when it exits the muzzle. To compensate for the movement of a double rifle while bullets are travelling down the barrels, it must be built with the barrels converging towards the muzzle (by a mysterious amount). Because different powder charges, bullet weights, rifle weights, shooter body weights, ambient temperatures, etc., all effect the way a rifle moves under recoil, the only way to balance these factors is by trial and error. This process is called regulation.

The goal of regulation is to make the rifle shoot both barrels to a common point of impact at a range appropriate for the calibre.

One can proceed generally in either of two ways: adjusting the relative position of the barrels or adjusting the load. If one has a fixed load in mind, the former method must be used. It involves repetitive unsoldering and resoldering the barrels until the required convergence is achieved, then relaying the ribs and finally refinishing the barrels.

A simpler method is to vary the load. The longer the bullet spends travelling down the barrel, the greater the force is exerted on the rifle to cause it to move while under recoil. If bullets from the left and right barrels strike the target too far apart at the desired range, and have crossed before they reach the target, the velocity is too great. The bullet weight must therefore be increased or the powder charge decreased. If bullets from the left and right barrels strike the target at the desired range too far apart, but have not crossed before they reach the target, the velocity is too slow. The bullet weight must therefore be decreased or the powder charge increased.

The construction of an effective double rifle is the apogee of the gunmaker's art. If, however, one comes into possession of a double rifle for which the original load is unknown, one can often make it shoot well by adjusting the load to the rifle.

 

[saltydog452]

Thanx..

Thanks for your response.

salty.