Hi. I'm have a shotgun question. This site looks chock-a-block with expert advice. I'd sure appreciate some. I'm thinking of buying an over-under 12 gauge.

I have read that when a double barrel shotgun is made the barrels are focused to the same point of impact at 40 yds. This is not done by diverting each to a mid-point, but by focusing one barrel parallel to the main axis and focusing the other to cross the first at 40 yards. With a cheap old 12 gauge SxS I own the left barrel seems to be parallel-to-axis and the left is oriented to cross its line-of-sight. Please correct me if this is incorrect theory.

My follow-on question is about O/U's. Assuming the above to be true, on an O/U is the lower or upper barrel the straight-on barrel? It seems to me that if the upper barrel is focused to cross the lower barrel its trajectory is steeply downhill after 40 yds. If the upper barrel is the straight-on barrel the lower barrel pattern is still rising after 40 yds. If I was going to poke slugs through it that is crucial information.

Thanks. W

Wretch,
It looks like you have the left barrel trajectory crossing the left barrel trajectory.

On a SxS you can find the center line of the gun relatively easily and the plane along the center of the gun has some significance. It is much harder to find the center line of an O/U barrel set and it does not have the same significance. The centerline of a O/U is simply a theoretical plane that is midway between the barrels so one barrel is not held to the center line and the other barrel matched to it.

All of that said, if you can get anything short of a London or Italian Best Quality gun to shoot to point of aim within a margin of error less than the distance of the centerlines of the bores from each other, then you really have a great shotgun. For most manufacturers, two to three inches of divergence between the POI of the two barrels at 40 yards is acceptable.

Shooting slugs in a double requires a much higher level of accuracy because it is a single projectile and not a 30" diameter pattern at the intended yardage. A gun that worked wonderfully well for upland or waterfowl shotgunning may be unsuitable for slug shooting or even turkey hunting with the super tight chokes.

quote:

Originally posted by Mort Canard:
Wretch,
It looks like you have the left barrel trajectory crossing the left barrel trajectory.

Thanks for the reply. You're right. Mis-type. Left is straight on, right crosses under. I found this out with slugs. Left bbl slug was essentially in line at 40 yds. The slug from the right bbl was significantly beneath and left of the left bbl.

Back to original Q, will an O/U toss a slug to 100 yds from both bbls or does one bbl do a nose dive after 40 yds?