Frame size and barrel regulation

[AmarilloMike]

We all know we can buy a Parker 12 gauge in 1, 2, and 3 frame. I have read here of a 12 gauge that is a 6 frame.

But sticking to 1,2 and 3 frame guns, say all with 30" barrels, how did they regulate them. I have been assured in many online discussions that quality doubles have absolutely straight barrels. So the 3 frame gun is an 1/8th inch wider at the firing pins than a 1 frame gun. So if the bores are absolutely straight then the 3 frame gun's right barrel would point more to the left than the 1 frame right barrel, 3 frame left more to the right than the 1 frame left barrel.

The extra "tow-in" of the 3 frame right barrel is 1/16" every 2-1/2ft (30")

So at 40 yards the 3 frame right barrel should shoot 3" to the left of the 1 frame right barrel (40x3)/2.5)*(1/16)=3". And vice versa for the 3 Frame left barrel.

And then how did Parker regulate that 6 frame 12 bore which has firing pins 5/16" wider than the 1 frame. ((40x3)/2.5)*((5/16)/2)=7.5" So the 6 frame barrels would shoot 7.5" to either side of the 1 frame barrels at 40 yards.

[Dean Romig]

With an effective normal 40 yard pattern of say twenty-four inches, IMHO I don't think 3 inches would effectively make very much difference in whether or not you killed your bird.

Three inches would be a critical factor for a double rifle of course.

[david ross]

Hi Dean.
Do not forget the 1/2 frame size and would this shoot the same as a 1 or 2 frame gun.
All the best Dave.

[Dean Romig]

Originally Posted by david ross

Hi Dean.
Do not forget the 1/2 frame size and would this shoot the same as a 1 or 2 frame gun.
All the best Dave.

And of course, the 1 1/2-frame guns which became very popular and common at about the turn of the century and eventually replaced the 1-frame.

I suspect they would all shoot about the same as only the barrels and chokes determine how a gun will shoot and pattern.

[Bill Murphy]

I have had this same conversation a few times. The bottom line is that shotgun barrels on double barrel shotguns are not always straight, almost never on "good" guns. I have been beaten to death by so called experts on this subject, but I am sticking with my original statement. I have a Lindner pigeon gun that is so far separated at the breech that it could have been made as an eight gauge. The muzzles are much closer. These barrels cannot physically be straight. They are swamped in like a double rifle, however little.

[Chris T.]

Can they be straight? Measure the center to center distance at the breach end and at the muzzle on any double any gauge and it will be different from end to end. If they were straight, the right barrel would shoot to the left and the left barrel to the right.

[Bill Murphy]

Thanks, Chris. Dragging out my #6 frame ten gauge right now violates my doctors instruction, but I will guarantee that the center to center at the breech is a whale of a lot bigger than the center to center at the muzzle. I will take back what I said about swamped barrels on double rifles, but I'll stick to what I said about shotguns.

[Big D]

Has anyone seen the muzzle spacing on the 12 gauge 6 frame? Maybe the spacing is wider than on a smaller frame gun, thereby eliminating the crossover pattern mentioned above

[todd allen]

When bore sighting a set of shotgun bbls, I like to use a de-primed cartridge case inserted in the chamber, to sight thru.

[charlie cleveland]

never thought of doing that...charlie