Double Rifle Regulation Question

[Ray B]

It seems to me that regulating a double rifle would be much simpler if the barrels were aimed such that the bullets ran parallel to the line of sight; that is, the left barrel maintained a path left of the LOS while the right barrel maintained a path to the right, both bullets impacting the distance apart that they are in the rifle. the regulation would then be to get the trajectory adjusted for the desired distance. I'm guessing that the dynamics of the bullet traveling through the barrel are such that this is way over simplified but it seems it would be one less thang to adjust..

 

[bruce moulds]

ray,
what you say makes sense.
crossing trajectories are only perfect at one range anyway.
the distance from centre of the bores is very little, and would be unnoticeable in hunting situations.
particularly with iron sights.
there is a high probability that many scope sighted bolt acyions have ther deadwind zeros that far out anyway, and the owners do not even know.
more knowledgable answers will be interesting.
bruce.

 

[Russ-F]

The rifle starts moving under recoil with the bullet still in the barrel.
The gun recoils in a slightly different path depending on whether the right or left barrel if fired.
Parallel barrels would shoot apart to a noticeable degree.
Having the barrels shoot together at a given distance (100 yards for instance) even if they start to shoot apart beyond that distance is much better than having them never shoot together which is normally the result of parallel barrels.

 

[Ray B]

I'm aware that the rifle is moving as the bullet travels down the barrel which is why I didn't say to just make the barrels parallel. The reverse push from the bullet will vary with different weights and acceleration. The gun is then pushed back against it's buttplate, which is not in line with the bore so some amount of torque is applied, resulting mostly in muzzle lift but also to one side or the other. So it seems to me that even how the gun is held will make significant differences in the direction the bullet takes. All that said, wouldn't it be better goal to have the route the bullet takes run parallel and inch or so to the left or right to the line of sight than to have it cross at some distance?

 

[bruce moulds]

what ray said.
different burning rates of powder for the same velocity will also affect where the barrels point as the bullet leaves the muzzle.
bruce.

 

[Russ-F]

Ray,
What you propose has the two barrel points of impact (centres of groups) being separated by approximately their bore to bore dimension (let’s say 1-1/2”) at all distances - which would require regulation to do. With conventional regulation what the gunmaker effectively achieves by getting the barrel points of impact to coincide at 100 yards (for example) is to have the barrels shoot closer together than 1-1/2” at any distance between the muzzle & 200 yards (i.e. converging from 1-1/2” group separation to 0” group separation from muzzle to 100 yards & then diverging from 0” separation at 100 yards to 1-1/2” separation at 200 yards). The net effect is a combined barrel group size always smaller than what your proposal allows. Yes, beyond 200 yards the divergence of conventionally regulated barrels would increase progressively more than 1-1/2"but long range performance isn't going to worry many users of double rifles.

From the gunmakers point of view they would still have to go through the expensive & time consuming regulation process to attain parallel barrel groups which you propose & the end result would be a larger composite group from both barrels at the test distance – the one that their rifle will be judged by. To be able to display the smallest composite group was particularly important during the golden years of double rifle production as the sporting press of the day organised some prestigious & well reported competitions between makers.

All the variable aspects which you mention (including ammunition related variation) would apply equally to barrels being regulated to shoot parallel to each other & those conventionally regulated.

In summation the conventional regulation is no more effort for the gunmaker (than what you propose) & has inherent advantages (over the parallel setting of impacts) at the distances the rifle would be expected to be used at.

Of course in practice in the field it wouldn’t matter much either way for all the reasons you’ve mentioned plus for some calibres of double rifle it's a achievement to find any suitable ammunition never mind the exact specification they were regulated for.

 

[frog stealer]

Guys,

Please read read Wright’s book “Shooting the English Double Rifle”. This book does a great job in describing the mechanics of barrel regulation.

 

[crs]

And this book tells you how to do it!
Building Double Rifles On Shotgun Actions
By W. Ellis Brown

 

[flatwater bill]

Regulating the barrels at one common point of impact is an achievable goal by the maker. They would not want to guarantee Ramanujan like performance of parallel to infinity. It would be difficult to prove with only one accompanying target in the leg of mutton case........................FWB