Adjusting Point Of Impact


Dear Sirs

I have a Browning Special Sporting that patterns its barrels at 2″ and 5″ high at 40 yards, respectively and would like to have my top barrel altered to shoot 2″ high. I would like some advice on what is my best option to achieve this along with approx. cost and where to find a company to have this performed.

Thanks

Dan

Dear Dan,

Well now, there it is. Shotguns will just do that. I don’t know how you checked your point of impact, but the usual way is to use the same Full choke tube in each bbl and whack away at 40 yards. You can also do it at 20 and double the readings. This is probably easier and full choke gives you a more definable pattern for easier measuring.

3″ variance at 40 yards is not very much and would be considered pretty good by most gun makers. Remember, Browning is quite proud of the fact that their Japanese guns have bore measurements of “only” +/- .003″. If you gang that with the same variance in chokes, you can go .006″ either way. That is an entire ton of variance, but with modern production that is the fact.

If they have that much variance in bores and chokes, it stands to reason that point of impact can vary a bit too. And- Browning Japan (alias Miroku) has pretty good quality control too when compared to other makers. Shotgun are not rifles and you may have to learn to live with it. Very, VERY few shotguns will have perfectly aligned bores at 40 yards.

The basic design of the O/U shotgun “wants” to toss the top barrel a little high. It is far more the rule than the exception and is due to the fact that the top barrel sits higher in the action. Do you think 3″ high at 40 yards is a lot? I had a Perazzi Comp 1 trap gun that shot its top barrel 18″ higher than the bottom at 40 yards! I had a Belgian Browning 12 gauge Superlite that was almost as bad. I shot a whole bunch of grouse and woodcock with that Browning until I found out about the barrels. It destroyed my confidence in the gun and I sold it.

What is the fix for improper barrel convergence? The usual fix is to take a piece of paper, tape it to the stock and write “Gun for sale” on it. If you just can’t live with it, there are two other approaches.

The easy way is to use an eccentric screw choke. In the old solid choke days (good old?) the choke on the offending barrel would just be recut slightly on a bias. This was a very common adjustment and could influence the pattern a small amount in any direction. I had this done to a 28 gauge Parker Repro that threw the left barrel half a foot to the left. I lost a bit of choke, but the convergence was perfect. Today, with screw chokes, you just get Briley to cut you an eccentric choke. I have never used one and imagine that you would have to be quite careful in seating the choke by an index mark, but Briley does offer the service.

The other way of adjusting point of impact- the right way- is to pull off the side ribs and reset the barrels just like they originally do at the factory. It is expensive and takes and expert with a test range. It also requires rebluing. It is much easier to take out that piece of paper and write “For sale” on it.

One last thought. When possible I ALWAYS try to buy my O/Us used. This gives me the chance to test before buying. The first test that I make is always to check barrel convergence. I can change point of impact by altering the stock, but barrel convergence is built in. I have been burned by improper convergence enough to be very wary of it. Welcome to the club.

Of course, if you shot gas guns, you would have no trouble getting that single barrel to converge properly, now would you.

Best regards,

Bruce Buck
Shotgun Report’s Technoid
(Often in error, never in doubt.)

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