doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Gun reboring and regulating.

Most likely all that has been done is the chokes have been opened up. Perhaps shot to see what the pattern looks like if you requested it for a specific load and to make sure they are close to where expected.

I often chuckle aloud when I hear some shooter claim his misses are the result of a gun not shooting to his point of aim because the pattern was 2" high or 4" off at 30 or 40 yards. Take a 2 X 4 and stand it at 30 yards with either edgewise or large side facing you. Then take a 30" circle of cardboard and nail it to the 2 X 4 and see the relationship of your pattern to the 2" or 4" point of impact error. Perhaps 6" or more at 40 yards is a problem but not a couple inches.

Real problem many shooters have is estimating distances and perhaps too tightly choked bores. If your gun is too tightly choked your pattern will be smaller than expected. If you can not estimate distance correctly your leads will never be correct. A 30" pattern gives you what in reality is a plus or minus 12-15", call it one foot margin of error, for centering the bird or target, because the edges of any pattern tend to be very thin.

Do the math. If a crossing bird travels say ten feet at thirty yards while the shot travels 30 yards and is centered in your pattern, if it travels more than eleven feet at 40 yards, which it will, you will miss if you do not know the difference in distance between 30 and 40 yards and change your lead. Some will point out the pattern spreads more in distance but it is a cone shape not a cylinder so a 30" pattern at 30 will be larger and more full of gaps at 40 yards or tighter and smaller at 30 yards if 30" at 40 yards. Get the distance right to get the lead right or every shot is largely luck.

I did the calculations for Teal once and figured I needed to be within 2 yards plus or minus to hit them with consistency at 30 to 40 yards. Since they are still in great numbers I never master the distance estimation in their case but I still love shooting them.

Now if you really want to get it right you need to figure angles into our equations, as well as distance, but I left my pocket protractor at home. On a 90� crossing bird the lead is more than at 45� or at 30�. We will leave deflection, raising birds, speed changes, and falling birds for another day.

Kem, I would think the only way to receive a suitable answer to your question would be to talk with the man who did the work, and see what he means by regulation.

SRH

Not quite certain I am following you here. What exactly are you saying the barrels are parallel to.

If you have two tubes of equal diameter and lay them on a surface table the they will be on a horizontal plain .Gun barrels are put together so that they are parallel in the same way . It is so when you look down them one tube does not stand higher than the other .

Kem, basically your man has bored your bore you chokes out .

OK, Gunman and others, typically are the tubes joined perfectly straight or do they have a slight curve in the bores? That is, are they pulled together along the way to the muzzle to get them to shoot to basically the same point of impact at say 40 yards?

I have 'properly' patterned one gun .... that is to say, 5 shots from each (pre dirtied) barrel at 40 yards with a given cartridge, draw 30" circle (afterwards) - count pellets and work out percentage. Honestly - hard work with 6' square paper sheets that catch the slightest breath of wind. Didn't learn much - except its hard to do! Resultant patterns were a little tighter than the bore dimensions indicated, but the cartridge used had a plastic wad.
I have shot about half my guns at a pattern plate during fittings. This was to adjust the stock dimensions to shoot where I thought it should. None of my guns showed any significant difference between left and right, or top and bottom in the pattern centre. Where they shot LOW, or LEFT, stock alterations have been made.

Well yeah Sure, I'm not a Gunmaker of long years experience but have basically realised this ever since I owned my first SxS back in 1955. Quite obviously one doesn't want one of the barrels pointing up toward the Sy & the other Down toward mother earth. This is so elementary is not really worthy of mentioning. What may not be so obvious to some but should be if one uses any power of observation is that the two barrels "Converge" from breech to muzzle, All The Way Down. That my Friend is where the "Regulation" occurs. Even if they were calculated out where to sit & so set at their original assembly with no further adjustment made to them they were regulated. Admittedly some guns get more care in this regulating than others & hence are apt to "Shoot Together". As stated earlier by another poster barrel regulation & choke regulation are entirely two different matters. Both can be done with great care & consideration or both can be done on a Hit or Miss basis. A "Good Gun" doesn't just have the barrels thrown up there & soldered in where ever they happen to land.

Piper , One day you and I will see eye to eye over something .I live In hope .
Those who have never worked in a barrel shop may not fully understand how they are made on a production basis .Look up YouTube there several good examples .
Gunmakers , Purdey , LC Smith or AyA machine a standard action body with predetermined striker centres. The barrels are made so the centres at the breech match those of the action .

Barrels are made in lengths from 25" to 30" based on these centres, they are put together so as the tubes touch at the muzzle with the tubes straight ,no bows or bends , that's it .
No one has calculated convergences if they had you would never see a side by side with tubes that touch at the muzzles .
If you compare an older Grant with wide centres to a modern gun like the AyA that has narrower centres both with 28" barrels it will be obvious that the two guns can not possibly shoot to the same place at the same distance so how can they be regulated?

Fact is had you asked me 30 years ago I would have said the a 28" SxS would have had over lapping patterns at 30 yards , 15 years ago I found I was wrong and it came as quite a surprise .

The problem that long held beliefs often compounded by well intentioned writers who have repeated these without question as they were told it as "fact" are hard to put aside, so there is no point in Me saying anything that is untrue as it is my credibility at stake .
I can not explain any clearer than I have tried to and hope that those reading gain some understanding of actual gunmaking process not "what every one knows ", dispelling a few myths along the way .

Yes i am quite aware that the barrels are set in as straight as possible to make them & are not bent. I am also fully aware as would be anyone who has followed this board for any length of time with an open mind that it is not 100% given that "ALL" muzzles touch one another on a factory original with un-cut barrels. Numerous instances have been reported on which they did not touch & with barrels which lettered as original to the gun. These will nearly always be found on guns having barrels in the area of 26" length. Obviously there was a reason for this. In drawings extant from the US maker L C Smith, precise angles at which the bores are set to one another by them are given. Also shown is the point in front of the muzzles where a continuation of the bore axises would cross & the distance apart which this same continuation would have at 40 yds. I can assure you that if the gun actually placed its load at the exact point to which the bores point in a static position success with a SxS double would be virtually non-existent. When I used the term "Calculated" I was not necessarily speaking of doing a long mathematical formula, but this most likely came about through trial & error in the early days of double making. Whether you choose to admit it or not, to assemble the two barrels in such a matter as for them to place the load from each barrel to as near as possible to the same point "IS" their regulation. I am not implying here that shot barrels are continuously shot & tweaked but that they are assembled to a pre-determined regulation. There is of course more leeway with a shotgun than a double rifle, but never-the-less for success it is necessary that both barrels shoot to very near the same point.