Harry I didn't mean to anger you, but you are simply not correct in this case! If the centers of each barrels individual groups from a double rifle is crossing at any distance then the load is not proper for the regulation of the rifle.
Like you I have been in the double rifle business for some time, quite a bit longer than you in fact.I have been hunting, and loading almost exclusively with double rifles for 53 years,since the age of 21 yrs.
I bought my first double rifle in 1958 when I was 21 years old, and have owned over fourty double rifles since that time, and loaded for every one of them except one.
You are correct in that if the rifle is crossing at any range it will diverge more and more from that point down range. However if a double rifle is crossing at any range then the load is not proper for that rifle, close but not proper.
A composite group from a properly regulated double rifle shooting a properly loaded cartridge, that composite group will be slightly egg shaped along the horizontal line thorugh the aiming point on the target. The centers of each barrels individual group will always be on it's own side of the aiming point on the target if properly loaded.
As both barrel's groups go down range they will widen just like any other barrel, so that as the two groups get larger the right shots will spill over into the left group, and the left barrel's group will spill over into the right barrel's group, but he
centers of each barrels individual group will remain on it's own side of the aiming point the is in the middle of the composit group!
The missconception that the rifle is supposed to cross is the reason that people claim that the multi filp-up rear sights on a double rifle were put there for decoration only, and nothing could be farther from the truth.
If you look at those flip-ups you will see that the center line of all of them are in a perfect line. If the rifle were supposed to cross the centers of each flip-up couldn't be in line, and would be useless. They were not for decoration but work as they are supposed to if the rifle is shooting properly regulating ammo. An egg shaped composit group of 3 " at 50 yds will still cover an 8 " pattern at 100 yds on a cape buffalo's heart lung at that range, and shooting off hand most will not do better than that with a scoped rifle off hand. At 15 yards to the muzzles of the double they are dead on for stopping. Make no mistake you don't want to stand at 200 yds and let me shoot at you with the largest double rifle I own, hopeing I can't hit you with every shot!
Now none of this is to say a double rifle that is just starting to cross at 50 yds, is not usable that way, it is if you think a double rifle is supposed to do that, and you are willing to accept that type of regulation, but it is not correct regulation! In fact most factory ammo will not regulate properly in most double rifles, but is as good, or better than hand loads that cross!
I'm sure I have not convinced you of anything and that is OK, because as long as your doubles do what YOU want them to do, that is all that matters. Though disagree we may, nothing is lost, we both love double rifles and that is what counts in the long run!
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Good hunting!
