I have a combination gun with bottom rifle barrel soldered to top shot barrel.

1st shot from a cold barrel to point of aim. 2nd shot from warm barrel goes 4" high.

Now a double is regulated to put its two shots on target. But how close to aim are shots 3 and 4 and then 5 and 6 when the barrels get hot?

I assume there is counter warping - ie the right warps towards the left, but then counteracted from the left.

I don't have access to a double to experiment with - but interested in experience of those that have.

Yours sounds as if it is the reverse of my Savage 24 Turkey gun. Mine has the .22 hornet barrel on top of the 12 gauge shotgun barrel.

Shooting either barrel has not seemed to have any affect on the other barrel. I must confess though , I have rarely had to shoot either barrel more than once to take the turkey.
The only time the rifle barrel is shot often is when shooting prairie dogs.

I can’t say I’ve ever noticed a NOTABLE shift between cold barrels and hot on a well constructed double rifle.

I've heard the second barrel should be fired within 12 seconds of the first, and that rifles should be regulated to cope with that timing.

I suppose it is possible it may not work so well if the left barrel is fired first or if more shots are fired immediately. In the latter case, assuming a charge, regulation may cease to matter much, though.

I spent a day at the old famous shooting range in Ferlach, Austria, a town well known for it's gunsmith school and the several notable gunmakers stationed in Ferlach. The range building had a series of small forge blowers mounted on the wall above gun racks that supported break open guns so the barrels could be cooled between shots.

We were there with a gunmaker checking the patterning of my friends new gun that the maker had just completed. It had a 20G barrel set up for shooting Brennekke slugs and a rifled barrel in 5.7x57 if my memory serves me properly.

Like everyone using the range that day the gunmaker placed the open gun under one of the cooling fans for a few minutes between shots.

I assume these experienced gunmakers knew a thing or two about the effect of heat on the POI of double guns.

While I casually observed the shooting process I was more interested in the centuries old memorabilia that adorned the walls of the famous old range building. Coming from a young country in so far as white occupation goes, where anything 100 years old is ancient, it was a fascinating experience for me.

quote:

Originally posted by Heym SR20:
I have a combination gun with bottom rifle barrel soldered to top shot barrel.

1st shot from a cold barrel to point of aim. 2nd shot from warm barrel goes 4" high.

Now a double is regulated to put its two shots on target. But how close to aim are shots 3 and 4 and then 5 and 6 when the barrels get hot?

I assume there is counter warping - ie the right warps towards the left, but then counteracted from the left.

I don't have access to a double to experiment with - but interested in experience of those that have.

In the first place a combination gun/rifle is a Zebra of the different stripe than a double rifle and reacts to heat in different ways.

A combination gun is designed to primarily be a shotgun first and foremost for bird hunting where the shot barrel is used for multiple shots at winged birds. But the rifle barrel is most often a one shot affaire only when needed to pop a sitting rabbit, or fox. Normally the rifle barrel is not fired several times in a row.
To see what I mean by this you can fire the shot barrel several times at flying birds and the shot pattern will not change enough so that the shot pattern will shift noticeably to totally miss the bird on the wing. However if you fire the shot barrel several times the warp will be enough to show on the target with a bullet from the rifle barrel, different from where it normally prints even on the first shot with the rifle barrel.


On a double rifle, the regulation is consistent when two shots are fired and a reload of both barrels the shots will not show as much change for the second two shots which is normally the most shots taken with a double rifle, and the amount of heat change is evenly applied to both barrels. Where the combo gun a shot barrel will move slightly, but will move the thin rifle barrel in a way that shows more on the target than the shot barrel.