Picking Chokes


Dear Technoid,

I have spoken to you before about my newly purchased A303 20 gauge. I have really begun to like the gun after sorting out the ejection problems and have even managed a few 25 straights at skeet using the I.C choke that came with the gun ( very impressive hits on the corner stations ) , but seeing as there are no style points in skeet I have opted to purchase a Beretta skeet choke. When I changed the choke I measured them both, the I.C. measured .615″ which was much tighter than I expected, considering the hard hits I experienced on most shots. To make matters more confusing the skeet choke measured .635″, I measured the chokes with a vernier calipers and was unable to measure the bore but assumed it was the standard .615″. All chokes are factory Beretta. Am I wrong in assuming a standard bore ? I have not shot the gun with the skeet choke and it may prove to be the proper constriction for skeet but I am still interested in your opinion.

P.S. my normal skeet gun is a Browning Special Skeet 12 gauge with both skeet chokes measuring .739″ on a factory .743″ bore and it does not hit targets nearly as hard as the Beretta with the I.C. chokes.

Thanks for your consideration.

Steve

Dear Steve,

It sounds as though something is off kilter. My guess is that you will get different measurements if you can get your hands on a proper bore mike. It is tough to get really good measurements with vernier calipers.

I have not miked the Beretta 20 gauge bores, but the Beretta 12 gauge bores tend to run more than a couple of points tight. One of my 12 gauge 303 barrels runs .723″, but many other that I have miked are closer to .721″ and I have even seen some less than that. This is in an industry where .725″ is the de facto 12 gauge norm and .729″ is the nominal dimension.

If we assume for the moment that your 20 gauge bore is a standard .615″ (it probably is NOT), your skeet choke should measure sort of, more or less, around .610″ or .005″ constriction. Your IC choke should be maybe a bit less than .605″ or .010″ constriction. The .005″ and .010″ are common (but definitely not universal) 12 gauge measurements and the 20 is about the same. Notice that I am using the words “about”, “maybe” and “more or less” a great deal.

Not everyone adheres to the convenient .005″ skeet choke constriction by a long shot. In fact, most don’t. Beretta’s solid choke skeet guns from the ’70s (the 680 series) often had factory skeet chokes that were simply cylinder bore out to a slight flare. No choke at all. They broke targets fine with the older 32 gram Olympic loads. That said, I’ll bet that Ennio Falco used about .010″ in each barrel in his Beretta when he won the Atlanta Olympics Skeet medal with those 24 gram loads.

If you want to set your gun up with exactly a .005″ skeet choke, you must ACCURATELY measure your bore and then call Briley up and ask them to cut you a choke for that bore. They will be happy to do it. Their work is accurate in my recent experience (I had them do just exactly this for my 303 needing a .005″ and a .040″) and not expensive at all. Of course, if you are measuring your bore, you might as well also measure your chokes. It might save you sending something down to them.

Frankly, I don’t mind seeing a little smoke at skeet. I shoot a fair amount of skeet with my 12 gauge 303 and I have chokes in just about every .005″ increment. My best skeet scores over the past four years with that gun have come with .010″ constriction, not with .000″ or .005″. .010″ is a pretty standard 12 gauge ImpCyl number. My 20 gauge Briley skeet tube set for my FN has .005″ across the board in all gauges for the skeet chokes and .015″ across the board for the “sporting clays” chokes. They work find, but I know of plenty of sub-gauge shooters who use a bit more than .005″s.

One thing that you must remember, if nothing else, is that a given constriction will not necessarily produce a given pattern with a certain shell. .005″ constriction in one barrel will not necessarily pattern the same as the same amount of squeeze in another barrel. You hear it all the time, but it is true. Each barrel is different. If you are really serious about optimizing performance, you really have to pattern with the shell that you are going to use.

One of the best skeet shooters in the country does his patterning in an underground test tunnel made available to him. He starts with chokes that are too tight and grinds a little bit out every few patterns until he gets just what he wants. When it is over and done with, both barrels (he shoots an O/U tube set) seldom have the same constrictions- but they have the same patterns.

So, the best advice that I can give you is to have your barrel and chokes properly miked. If you are looking for a specific dimension and none of the chokes that you have meet it, either grind an existing choke out or ask Briley to cut you one.

Best regards,

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

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1 Response to Picking Chokes

  1. Kirk says:

    My 20ga 303’s barrel is marked 16.9 which should make it a .625″ bore. Naturally I don’t believe everything I read but in this case it in fact measures .625″—I had to take it to a gun shop for the measurements as my bore gauge only works on 12ga and 16ga and those guys had a gauge for all of the Skeet bores. Only choke my gun came with was a Briley Skeet and it gives .005″ of constriction. Still don’t have any factory Beretta tubes, I bought Carlson’s and they are dealing with a different set of numbers with these. Their “Cylinder” tube actually gives .008″ of constriction against my barrel’s bore. Breaks Skeet targets pretty hard, though. Definitely check the markings on your barrel but confirm with an actual gauge.

    Kirk

    Bore, n. Shotgun enthusiast’s synonym for “gauge” ; everybody else’s synonym for “shotgun enthusiast.” – Ed Zern

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