Barrel Convergence


Dear Technoid,

I was interested in your response to Steve (“Barrel Convergence Woes”) because I had just that evening re-read Brindle’s book “Shotgun Shooting”. On page 173 he writes, “However, the barrels of many over-and-under guns intended for trapshooting are purposely converged to shoot to different heights. Traditionally they have been set so that the lower barrel shoots a good deal higher than the upper one (adjustably so on an increasing number of models) but this is reversed in some newer models. A difference of six to 12 inches at 40 yards is usual. For most shooters this makes such guns more useful for doubles shooting as well as International Trap.”

Brindle goes on to explain in detail why this is advantageous.

Keep up the good work!

Dave

Dear David,

While I normally take everything Brindle wrote as Gospel writ in stone, I can’t agree with this one. The very design of the O/U “wants” to throw the top barrel high because it recoils above the main axis of the gun. I can’t tell you how many O/Us I have owned or tested which shot the top barrel higher than the bottom. I have never owned or tested an O/U, as it came from the factory, which shot the bottom barrel higher than the top.

That isn’t to say that it wouldn’t be a good idea. I am sure that some people would love to have that bottom barrel high and top barrel flat. I remember a Perazzi trap gun which had a non selective trigger set to fire the top barrel first. As this is not ideal for recoil purposes, I always felt that it was an effort to get the first barrel high and the second one flat with out actually going to the expense of barrel regulating.

I set my International Trap guns up to shoot dead on both barrels. I find it easier to build in the right vertical lead mentally just as long as I know where the gun will shoot. Even with a high shooting first barrel, the leads on a flat bird are very different from those on a vertical rocket. I am too busy correcting for that the bird is doing to also be trying to remember that my barrels shoot to different points of impact. Clearly, ATA-style American trap is a different game with a fixed vertical component where it definitely does pay to have a high shooting gun so that you don’t have to cover the bird and shoot blind. ATA trap and Olympic bunker trap are very different sports. I have no experience with the new Olympic double trap, so I don’t know what is needed there.

Regulating barrel impact on medium priced shotguns is usually what turns them into high priced shotguns. I have personally owned both Belgian Brownings and Perazzis which shot the top barrel so high that I sold the guns once I discovered it. One Perazzi’s top barrel shot over a full pattern high at 40 yards. They just never took the time to test the point of impact before they boxed it up and shipped it off.

Changing point of impact of one barrel can be a real pain. You can recut the choke on a bias (I had this done to a Parker Repro with a left barrel which shot way left) or install eccentric screw chokes. Of course, it is never best to have your shot take a right hand turn just before it exits the barrel, but a little tinkering for a modest change isn’t too bad. Everyone does it.

The proper way to correct a bad convergence problem is to unsolder the barrels, realign them, test, realign again, test and final solder. It is expensive to do and that is why even some expensive guns aren’t regulated properly. One of the big advantages to the Krieghoff K-80 (other than the fact that you get free-weight exercise every time you hoist one) is that they have interchangeable barrel hangers so that you can adjust your own barrel convergence. Very handy.

That’s it. I’m out of ink.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC

Advertisements
This entry was posted in Shotgun related and tagged . Bookmark the permalink.

2 Responses to Barrel Convergence

  1. Carlyle H Pack says:

    I have read this article and the comments. I have found it very useful and convinces me that I have a problem with barrel convergence. I have a Browning two barrel set, .410 and .28 ga. The .28 ga is the problem, I used a static barrel alignment process. Bore sighting both barrels against the sight alignment at 20 yards then extrapolated the 40 yard measurements. This is what I found. At 20 yards the top barrel was 2 1/2 ” LOW below the line of sight, and the bottom barrel was 3″ ABOVE the line of sight. At 40 yards the measurements were : top barrel was 3″ LOW, and the bottom barrel was 8.8 ” ABOVE the line of sight. I think I have a problem, and I am seeking a solution. I shoot sporting clays on a regular basis. I will price a “Barrel Convergence” job and as a last resort split the barrels a quarter of the way back and insert a wedge. As crude as this sounds, a look at my drawing suggests this might be a solution.

    Like

  2. Hassan Abouzeid says:

    Bruce,

    I own a Berretta SO4 trap gun, and the bottom barrel has a POI 6″ above the top barrel at 40 yards. Horizontal alignment is perfect. Berretta SOs are high grade hand finished ones, and Beretta confirmed to me that it is a deliberate design feature, given the sharper rise of targets in the first shot (shooting trap). I find it a slight annoyance when shooting other disciplines like Helice (electrocibles) and sporting clays, which have targets that behave differently. Just my 0.02$, shoot safely!

    Hassan

    Like

Leave a Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.