Point Of Impact And Convergence


Bruce,

I have a Beretta 682 Sporting that I use for skeet. It fit me perfect right out the box, & as I recall, both barrels had good points of impact. This past grouse season I purchased a Beretta Ultralight, & it didn’t feel right. It pointed high (saw too much rib) & to the left when I mounted it.

I sanded the stock to the point where I can now see straight down the barrel & the rib appears flat. However, when I checked it out by shooting skeet, I did poorly. (I shoot low gun using the Orvis Method). I don’t think the gun is too whippy, as I have 28 inch barrels, & I occasional shoot my Buddy’s 28 Ga O/U with excellent results.

This past week, I checked the point of impact using full choke at 20 yards with light skeet loads. The bottom barrel was 6″ low, while the top was right on. Is this difference between top & bottom barrel bad enough to get Beretta to fix it? Is there a good reason for this difference?

Does muzzle jump occur fast enough to lift the point of impact? Should one expect to see more rib on a field grade gun? I suppose I should now repeat the above tests with my actual field loads. I reload 1 1/4 oz. of hard #7 shot for grouse. For pheasant, I buy premium shells with 1 1/2 oz of lead. The kick is noticeable. Because of the large muzzle jump, I can’t get off a second shot with my usual rhythm when necessary.

I would appreciate your help in correcting this problem. I have thought of shooting the top barrel first, but would have even more muzzle jump than before.

Thanks,

Glenn

Dear Glen,

Welcome to the world of a light gun. The lighter a gun is, the more perfectly is has to fit you in order to perform adequately. With a light gun (and especially with heavy shells), any little flaw in gun mount or stoppage in swing will be magnified. Of course, we have to use light guns in the field or our knuckles will be dragging on the ground. It’s tough to grouse hunt toting around an 8# target gun for six hours. That Beretta Ultralight seems like just the right medicine for grouse.

Barrel convergence first: The basic design of the O/U “wants” to shoot the top barrel higher than the bottom because the axis of the top barrel is higher. To counteract this, the manufacturers build the barrels closer together at the muzzle than at the breech so that they (in theory) converge at a certain distance. At least that is their intent. In fact, they usually are off by a bit and most O/Us shoot their top barrels higher than the bottoms in spite of the convergence at the muzzle. The heavier shell you use, the more you will notice this.

Is 6″ high at 20 yards too much? I think so. A top barrel which shoots 6″ higher than the bottom barrel at 40 yards would be right on the edge of acceptability. That 6″ at 20 yards will grow to 12″ at 40. That’s too much when you figure that your killing pattern on pheasant from a full choke at 40 yards isn’t over 18″.

Some hunters don’t mind it if the bottom barrel shoots high, figuring that the first shot is at a rising bird. Unfortunately, the O/U wants to do just the opposite, as your gun does, and throw the top barrel high, not the bottom. You are very right when you say that shooting the top barrel first would increase muzzle jump. You generally want to shoot the bottom barrel first as that puts the recoil in a straighter line. You could shoot your screw choke gun top bbl first, which is a bit high, and then use the flat shooting bottom barrel for the second shot. It might work if your first barrel is always on a rising bird. Personally, I very much prefer that both barrels shoot to the same place. Knowing that one of my barrels doesn’t shoot where I am looking would drive me looney. Life is too short to deal with that.

To do a proper barrel convergence test, use the same full screw choke in each barrel and test it with your full power hunting load, not with a light target load. It makes sense to test at the distance you feel you will take most of your birds. If you feel that you will shoot as far as 40 yards with that top barrel, then test at that distance. Test by aiming the shotgun like a rifle, but do it standing up or the recoil will kill you. Use an aiming point on your piece of paper and take three or four shots from the same barrel/choke/shell on the same piece of paper, so that you get a good pattern overlay and can really tell where it is striking. Then do the other barrel. Read your patterns from the back of the paper and the holes will be easier to see. But remember, that your are judging point of impact (where the center of the shot cloud is) rather than any kind of pattern percentage. That’s something entirely different.

If you do try to send the barrels back, I would be very interested in hearing what Beretta’s service department response is. Be prepared to wait, that’s for sure.

#7s on grouse? Good for you. It’s the classic New England ruffed grouse pellet, but you have to special order them and it’s a reloading only deal. On my grouse gun, I use one ounce of #7s in my cylinder bore barrel and #6s in my Modified barrel. I know that #6s seem heavy for grouse, but over the years, I’ve had marvelous luck with them. You just go over and pick your bird up, rather than have the dog hunt around for it. For pheasants I like #5s, but everyone has his own ideas on that.

Best regards,

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

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