Barrel Convergence Again


Dear Master of Lead Scatter:

I recently purchased a longer set of O/U barrels (from Beretta USA) for my 682 Gold Shotgun. I had these barrels fitted to my receiver by a gunsmith who specializes in Beretta shotguns.

Unlike my shorter set of barrels, this set throws shot–how shall I put it–“Willy Nilly.” That is, the bottom barrel throws a pattern that is blatantly well below my point of aim, and the top barrel throws a pattern that is ‘Way on Up High.’

Basically, I’m shooting about a 30/70 pattern with my lower barrel and a 80/20 pattern with upper. I established my conclusion using time proven, scientific patterning of 100 factory loaded Winchester AA 7.5 shotshells. Also, both barrels were fired with screw-in Full chokes at 40 yards. And yes, I counted the pellets (whew!).

Aren’t the patterns from the top and bottom barrels meant to converge on the same spot? Are my barrels poorly fastened together if they’re throwing shot here and yon? How expensive is a problem like this to fix, and is the fix really just a slippery slope to Messing Things Up Royally?

I can’t sleep at night from the nightmares and cold sweats since I got my shotgun back from the ‘smith. Can you help?

Sincerely,

Russ

Dear Russ,

I have bad news and I have a tiny bit of good news. Yes, both barrels of the gun are supposed to shoot to the same place. If you are 30/70 and 80/20, you have a definite barrel convergence problem. You should go to Beretta and howl. They may give you a bunch of mumbo-jumbo about that being “within factory tolerances” (translation: you lose), or they might actually admit that there is something grossly wrong and do something. What ever it is, it won’t happen quickly.

It’s very common for O/Us to shoot the top barrel higher than the bottom. It’s just part of the design of the gun and the axis on which the gun recoils. The top barrel is on a higher axis so it tends to raise more at the muzzle when it’s fired. Of course, this is nothing new and should all have been figured out at the factory a hundred years ago. I’ve had a Perazzi, a Parker Repro SxS and a Belgian Browning that also had the problem you describe. SxS guns have left and right convergence problems. These things should be corrected during manufacture, but mass production lets some mistakes slip through.

What to do? If going back to Beretta doesn’t work, you might try getting Briley to sell you some eccentric chokes. Briley Manufacturing, 1230 Lumpkin, Houston, TX 77043, tel: 800-331-5718, <www.briley.com>. They will make chokes that are off center in such a way as to correct your problem. You will have to remember which choke goes in which barrel and you will have to index the chokes correctly each time, but they can do it.

I don’t think that it is practical to try rethreading the barrels for a different kind of choke, but you might ask just in case. It is quite possible that the barrels are properly aligned and that the threading for the choke tubes is not in alignment. Happens all the time.

If the barrels aren’t properly aligned, it would be theoretically possible to resolder the barrels and redo convergence. My guess is that the expense of this makes it impractical for a medium priced gun.

I wish I had better news or easier fixes, but I don’t. More guns have this problem than people realize. It’s just that the average guy doesn’t every bother to do the testing that you did, so he doesn’t know why he is missing all those birds. You do and at least you can do something about it. Either fix the gun or sell it or the barrels. You can’t shoot it the way it is.

As an aside, when I buy a used gun, barrel convergence is the first thing I always test during my “return” period. If it’s a solid choke gun and it’s not too far out, the choke in the offending barrel can be recut at an angle. You lose some choke, but at least the gun shoots straight. I did this with my Parker Repro. Another alternative with a solid choke gun is to send it to Briley and have them install their screw chokes at a slight angle. It’s amazing, but they have the machinery to do this. If the gun already has factory screw chokes in place, as yours does, the options are pretty much limited to buying eccentric chokes.

Bottom line: contact Beretta. Ask them what their acceptable factory convergence variance is. You are going to be amazed at what you hear. Tell them that your variance is unacceptable (it is) and go from there. It may be helpful to root through some of your patterns and come up with a description of the variance in inches between the centers of the patterns. That shows the true lack of convergence. Some companies feel that a 5″ separation of pattern centers at 40 yards is perfectly normal. Some will stick you with even more. I don’t know of any that consider 10″ to be acceptable. At 40 yards 1-1/8 oz of #7-1/2’s only has an 18″ effective pattern on a trap view target. You shouldn’t have to give up 10″ of that due to some screw up at the factory.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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