Can this be correct?

[enfieldspares]

On most gun, except the makers claimed the Darne, the breech faces are at right angles. So I'm not surprised that when using laser designators that fit on the breech there was a problem. Best test for barrel alignment is the Mark 1 eyeball.

Dismount the barrels, clamp the lump in a lead jawed vice, look through right barrel see WHEN ALL IS CONCENTRIC where it aligns. Look through left barrel see where that aligns WHEN ALL IS CONCENTRIC. Now put gun away and relax!

As others have said it's in any case the front end that matters not the rear end (per se). Gunsmiths such as Ladbroke and Langton use a laser designator but it is one that fits in the muzzle and is adjusted to then be concentric at that place.

[Vince Green]

Nothing made by the hand of man is ever perfect, many older shotguns had their barrels made and aligned by hand in little backstreet workshops in Birmingham, Spain and Italy, and the result was only ever as good as the man on the day. Most were good enough, it was never intended they would stand up to bore laser scrutiny

Try sighting in a double rifle  and you soon realise that even "London Best" rifles are not target grade but they were never intended to be, 

[Robden]

11 hours ago, Scully said:

Hallelujah! Common sense! It never ceases to amaze me the lengths people will go to, to create problems for themselves which don’t exist! 
 

Now we're talking. This is one thing I am good at. 😀

[Scully]

57 minutes ago, Robden said:

Now we're talking. This is one thing I am good at. 😀

😂

[Gunman]

15/20 years ago John Foster well know in the trade for sleeving set up a laser test system to see where barrel point . His Idea was that when a pair of barrels were sleeved they could be set to converge at a set point .

His system used a tube with a lazer sight attached  that was entered into the barrels and was held centrally with sliding cones at the breech and muzzle . The barrel was held in a jig and sighted by eye at a target , the lasers then switched on so you could see where the centre line of the bores would shoot . This was not taking into account any ballistic effects of the cartridge . To ensure concentricity , that the laser was always true to the bore it was set up  by rotating the tube in vee blocks on a machine bed .

It was found in general that the average side by side barrel would have the right barrel shoot 10 inches high and 12 inches to the LEFT of the aim point and vice versa .Actual cross over points came as close as 15 feet from the muzzle at 30 yards.  Tests were made using a number of barrels taken at random including  guns from London  ,Birmingham , Scotland and the Continent .

O/U's tended to shoot top barrel flat and bottom up to 12 inches high , something that was confirmed shooting solid slugs through a B25 28" . The best gun tested , again out of various makes ,for overlapping patterns at 30 yards was a Simson non ejector .

If you compare a double barrel shot gun with a double rifle set up to shoot a 3 inch group at say 75 or 100 yards you will see that the barrels are spaced at the muzzle , shotguns in general are not . 

Fosters conclusions were that to make a pair of 28 inch side by side barrels barrels that would shoot over lapping patterns at 30 yards the muzzles would need to be spaced at some 5/16" between the barrels and have a rib or sight that stood 3/8"s above the tubes . O/U's would need less spacing at the muzzle as they tend to have narrower centres at the breech but would need a slightly higher rib to compensate .

There is a mathematical equation that can be applied to calculate this which I have some where ,that takes into consideration the distance between centres at breech and muzzle and distance to target .I will try to find it and put it up for any one to work out themselves .

 

[rbrowning2]

Now I know why a single barrel semi auto is such a great choice, just the one barrel to worry about.

[steve s×s]

On 18/05/2021 at 18:03, Scully said:

Hallelujah! Common sense! It never ceases to amaze me the lengths people will go to, to create problems for themselves which don’t exist! 
 

Only on pigeon watch, don't you just want to scream 😜