I've known for some time, the difficulty of getting barrels to the same point of impact.
And it it took " 5 or 6 " shots to hit at the same point....yeah right!
However, the barres do cross one another at line of sight, just from the welding process.
But just loading, and shooting one barrel you will find the ideal distance, with lets say the left barrel, then after the best load is found to give consistant, the start working on the next barrel, in no time at all you will find the second barrel comming close the first barrel.
When you change brand of powder, and batches of powder things may change, hence you might have to make minor changes to get the same results.
Have fun!
Best Regards
Old Ford