Skeet Choke Patterns


Dear Technoid,

I have read quite a bit about patterns and chamber lengths on your archives the Browning site and elsewhere, and decided to pattern my two Browning standard invector barrels, one with 3″ chambers, the other with 2 3/4″ chambers.

The reason is that I have gotten the bug for International Skeet, and wanted to see what if any pattern degradation I could expect with the same chokes, in two barrel sets made in the same year.

The patterning I did was at 70 feet because I expect most breaks on the Int. skeet field to be within a few feet of that distance.

My results were surprising.

30″ (2 3/4″ chamber) TOP BARREL Skeet Choke 32″ (3″ Chamber)

Core 48% Core 53%
Annular 35% Annular 35%

30″ (2 3/4″ chamber) BOTTOM BARREL Skeet choke 32″ (3″ Chamber)

Core 53% Core 51%
Annular 34% Annular 34%

The differences were about the same as that found between the 2 3/4″ barrels.

I also seem to have discovered a quirk that you may be able to explain. My I/C chokes had expected higher percentages in the 30″ “magic circle” but the ANNULAR ring was also far denser than I expected with percentages of shot the SAME or better than the Skeet choke.

Improved cylinder 30″ barrel

TOP BARREL 93% BOTTOM BARREL 89%
Core 59% Core 53%
Annular 34% Annular 36%

I “expected” the core to be hotter but it seems as if all of the stray shot outside of the pattern with the Skeet choke landed nicely in the annular ring without “overheating” the core at the expense of the outer end of the pattern.

It seems like these I/C chokes are a much better choice for my 7/8 ounce loads of hard 9’s and Int Skeet, or am I missing something? Did I find a pair of magic chokes?

Lastly, Many people have been touting cone work to even out patterns. Is there ANY chance that cone lengthening will pick up still more of those pellets outside the 30″ circle and get them into the fringe of the pattern? Are my annular ring densities suitable as they are for the Int Skeet birds?

I’m approaching this International issue wanting to be more certain that when I miss it’s because I missed, and not because I have holes in my pattern. I appreciate your insights to my questions.

Thanks and regards,

Gary

Dear Gary,

International Skeet? Welcome aboard! Tough game. A lot different from the miss-and-out American-style skeet. I competed in IntSk from ’74 to ’88 when Dryke and Carlisle were in it. I spent most of my time with 32 gram (1-1/8 oz) loads. Your 24 gram (7/8 oz) loads came after I had hung ’em up, so I don’t have much experience with them.

IntSk is a great game and today’s situation has a lot of advantages over when I was shooting. Today most fields have Beomats or All-Star machines that can easily be adjusted to handle the slow American skeet bird as well as the much faster International one. When I was shooting, most fields had only the old Winchester machines. They had to be tortured to throw the fast IntSk bird and often broke. This made range owners reluctant to turn up the fields for IntSk, so our practice opportunities were affected. Count your blessings when you load those nice new machines.

On the other side, IntSk was much more popular in the late ’70s and early ’80s than today. Our Nationals, where the Olympic team and off-year World Championship teams were selected, was a one shot “winner take all” event. If you had a qualifying average, you just showed up, shot for five days and the top two guys went to the Olympics. It was glorious. A civilian actually had a chance. You really were shooting for a spot on the Olympic team.

Today, there is a lengthy series of trials over an extended period of time. In theory, this selects more consistent shooters. In practice, we eliminate the great bulk of civilians who have to hold down a regular job. Without broad civilian support, the game has lost popularity. In a way, that’s good because there are now fewer people to beat for a team slot, but it’s a shame how participation has suffered. I think also that IntSk lost a lot of competitors to sporting clays. IntSk always was a game for cowboys, not accountants, and sporting clays fills that gap.

And now on to your question: Statistically, there is very little difference in any of the patterns you show. I don’t know how many patterns you took of each combination to arrive at your sample number or what your variance was between samples in each category. Generally, you should expect at least a 5% +/- variance over a long string of patterns. That means if you average 88%, you will also have some 83% and 93% patterns. All your patterns fall into this range, so statistically they are identical if you only took one or two samples of each. If you ran a long string (ten or more) of each, then the numbers start to take on a life of their own.

Using Ed Lowry’s neat (now defunct) ballistics program (“Shotshell Ballistics for Windows”) an 88% pattern (30″ circle at the distance the target is broken) of 7/8 oz #9s using an edge-on 110 mm clay gives a killing pattern of 22″ in diameter. My definition of a killing pattern is taken from Warren Johnson’s “Choke Chooser” as an 80% chance of a two pellet hit or a 95% chance of a one pellet hit (both statistically equal). You get that percentage right at the edge of the 22″ pattern. Obviously, it’s higher the closer to the center you go.

Lowry’s program is based on Gaussian distribution of patterns and is supported by most ballisticians today. If you run the numbers, using 7/8 oz of #9s (pellet count 512 nominal) and the 80%/2 hit or 95%/1 hit criteria, any pattern between 80% and 90% will give you the maximum killing circle. Tighter and looser patterns diminish the diameter of the killing circle by a small amount.

So, if any pattern from 80% to 90% will give us the optimum size 22″ killing circle, and if we can expect patterns to vary +/- 5% pattern to pattern, it would seem that a pattern average of 85% would be optimal.

Of course, we are making a bunch of assumptions here. The IntSk target is physically harder than the AmSk target, so you might want to adjust upwards the number of hits required for a break. With the higher velocity of todays ISSF loads, I don’t think that’s necessary, but that’s a personal choice. You may also have found that one of your chokes is more consistent that the other and would thus give that choke the edge. You may also want to choke up or down depending on where you are able to take your doubles. You may choose not to choke just for that second doubles bird on #4. Up to you.

Bottom line: all the patterns you show me are in the ballpark.

Will lengthening the forcing cones help? Dunno. Browning (Japan) went the overbore, short cone route. Why didn’t they elongate the cones while they were at it? It wouldn’t cost them any more. Could it be that they actually had a reason for not going to long cones? Long cones are one of those “Gee, it sounds like something for nothing” deals. In theory, they ease the transition of the shot into the barrel, thus resulting in fewer deformed pellets and more consistent patterns. In practice, this theory works best with large pellets. Small pellets, like your #9s, have a very nice flow regardless of the cone. There may be an improvement with cones up to 2″ long, but it may not be a noticeable improvement.

The downside of long cones is an increased chance of gas blowby and wad obturation failure. If you shoot a great deal in cold weather, this is a consideration. This is the reason that all shotguns don’t have long cones. There is a trade-off.

Long cones are also touted (by the people who sell the service) as reducing recoil. Maybe. BUT if you notice reduced recoil from cone lengthening, I’ll bet that you are also getting reduced velocity.

So, in the world of benefits from lengthening cones, I’d have to say that the 24 gram #9 load you are using is the least likely of all to show any benefit. Shot column is short and pellet size is small. I’d skip the cone lengthening and spend the money on practice.

Lastly, you shoot a 32″ Citori for IntSk?! You da man! How can you move that chunk of iron back fast enough to catch the blazing IntSk double? Good on you. I’d have to spend a lot of time in the gym to be able to do that.

Best regards,

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

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