In the US, most gun clubs have one or more wobble traps. These are regular traps normally used for ATA tournament events, that have an additional motor that allows the target altitude to vary, unlike ATA where the trap is set to one target height only. Gun Club managements likes them because they expand possibilities for "meat" shoot events, "Iron Man" events, and the like especially around the Thanksgiving/Christmas holidays, for a small increase in a trap's cost.
If you have no bunker within reasonable distance of you, then a nearby wobble will give you a sense of what bunker shooting is like. However, there can be a large leap between the two. That is, shooters who learn to shoot wobble very well quickly realize that skill set does not translate sufficiently to enable similar scores on the bunker. The biggest differences come from the fact that wobble is just a bit too easy, in part because too many of the targets are essentially closer to being straight-aways as opposed to the greater number of acute angle targets encountered on bunker. It is unfortunately also very easy to fall back into the rapid pull-bang, pull-bang, pull-bang shooting quite unlike bunker but common to ATA/PITA and still realize decent scores.
(If no club wobble is available, for a private wobble trap, expect the construction cost to run between 8 to 15 thousand, depending on the extent of amenities. However, you may want to install the trap at ground level to comply with the ISSF rules, then fabricate a plywood 'house" to allow the field to also be used as an ATA field. Make certain the trap machine model you purchase is guaranteed to throw targets at a 45 degree angles and to the ISSF-required 76 meter (83.1 meter vs ATA's 50 yards) distance with international targets. Also, confirm the trap is designed to easily do vertical field specific limit adjustments.
Beomat wobble trap loaded with White Flyer International targets.
If a new, exclusive, wobble is being constructed, consideration might be given to the Canterbury Trap Company's new computer programmed wobble system that emulates the 15 machines in a bunker. For a pretty neat demonstration video, click on the link: www.canterburytrap.co.nz. (Project 2000 shooting Range in El Cajon, CA has one, as does Santa Ynel Valley Sportsmans Association, also in California.)
To start with, consider shooting station 3 only as this will be the closest to what you will experience on a bunker with its true +/- 45 degree targets. Shooting stations 2-3-4, however will allow you to experience move and shoot, but the hard angle targets will be more than 45 degrees, depending on how the trap is set. Good practice though.
Another reason to shoot only station 3: in any given bunker scheme, some stations will be more difficult for you than others. For example, on one bunker station (scheme 2, station 1) the right target will be a 1.8m 40 degree target that requires a smooth, drive through the target without hesitation to break. The straight-away may well be at 1.5m. Then a tough 3.0m 45 degree left hand target needing a lot of smooth gun movement and speed to break it. With this combination, for the first two passes, you can't favor any target as you don't know (unless the computer isn't truly random) which target you'll get. A wobble trap's Station 3 will emulate this situation every time, as you never know what target you will receive and you will have to set up to expect anything every time; unlike in bunker where, if you're paying attention, you often will know later in the round which target you will get (but you better be right!) and can make adjustments to favor that target.
In the ISSF version of wobble (the rules call it Automatic Trap, some other names include: Automatic Ball Trap, Continental trap), the shooting stations are on a large straight-line, flat and even, safe platform (see ISSF/USA Shooting rules P241—like a bunker field—whereas the US wobble will have the standard ATA arc, with its economical-to-construct concrete fingers, often with dirt or grass below the finger's height. See the ATA rule book for the construction layout information on P47 and P55. Where the ATA field has a little "house" for the trap, the ISSF specification calls for the trap below ground, with the trap roof at the height of the shooting station. A few clubs have built a platform the height of the ATA house to get the equivalent of an ISSF ground level Automatic trap with the shooting platform, at the same height as the trap roof. Alternatively, It is perfectly practical to build an ISSF below-ground trap installation, then exchange the ground-level roof for a ATA-conforming "house" for tournament use, as mentioned earlier.
Picture above shows one system of portable platforms to make an ATA trap field into the equivalent of an ISSF ground level trap installation. This style is easy to move when the field is needed for ATA events, but makes following the ISSF rule's shoot-and-move shooting procedure impracticable. Probably, the best arrangement is a platform with ramps.
In hot areas, a sun cover over the shooting stations makes a big difference to shooters comfort. Similarly, in rainy areas a rain cover is useful. There, a half shed keeps the rain from blowing in to the rear making the venue comfortable to shoot in all types of weather conditions. Very few wobbles are equipped with any kind of cover in the US because of ATA handicap event needs.
It is best if the wobble has a microphone release system. All bunkers have them and if you are going to have "call" issues, then this is a good time to get them resolved. Some shooters, because of their voice characteristics, have trouble getting the microphone system to release a target when they call for it. Pitching your voice lower or accentuating the "P" in the call "pull" are two changes that can be made to possibly help. Women are more likely than men to have "call" problems (Women may want to note the special low-pitched calls used by the Italian team's shooters in the 2008 women's World Cup skeet final video, at Suhl, Germany on www.issf-sports.org. Type "suhl" into the search box, then select "2008 Women's skeet". Yes, ISSF/Olympic skeet uses microphones!). If the club doesn't have mics on your field or you want to shoot at odd times, a Clay delay personal microphone system works very well. Click on the link for more info.
Trap setting: Most ATA wobble fields have the standard ATA distance spring as the field is usually used as a regular ATA field with the verticalizing motor shut off. To get the maximum out of the wobble experience and make it more like bunker, at least a stronger spring or PAT trap extra band needs to be acquired to throw the target 76 meters or 83.1 yards (See ISSF rules). While some few machines can throw ATA targets to the 76 meter mark, you should be aware that excessive target breakage can be a problem and the only recourse is the purchase of true International targets. Alternatively, as a compromise, the spring can be backed off. . . The ISSF rules allow a legal wobble angle of only 30 degrees and some ATA houses will only allow this degree target as the trap is set too deep in the house. Obviously, to get near-to bunker practice, the trap needs to throwing the maximum extreme 45 degree target.
A special note about vertical field setting: The biggest problem with ATA club wobble traps is mis-adjustment of the vertical field (The PAT trap does not have this problem). Usually, the lowest target is from 0 to about a half-meter in height. Since the club management usually doesn't want to throw a 76 meter target or perhaps even adjust the vertical field, it means that this low target will hit the ground at around 35 - 40 yards (Unless the trap is on high ground at a cliff's edge. . . ): not enough time for most shooters to have a chance to use the second barrel if needed. Usually, a super low target is very hard to hit and the second barrel becomes a necessity, but it's only usable by the very fastest shooters. Sometimes. It's hardly fair. And certainly not the best practice for bunker.
If you think about it, a 1.5 meter (lowest) target comes roughly to the eye level at the 10m measuring point and continues climbing. The lowest target should not be a grasscutter. Targets set to the 1.5 minimum will enable some very good scores and will be fair to all shooters, even the slowest. They also go a long way to minimize the penalty caused by the high ATA/PITA house as the target is clearly visible and the usually club-set slow target allows plenty of time to break it. Club management often will tell you they can't or won't set the vertical field, but sometimes a quiet diplomatic discussion with the club's trap mechanic can resolve the problem.
The ISSF rules: section 9.19.1, list the vertical field settings. Note the target is set at 10 meters out and the lowest target is 1.5M and the highest is 3.0 meters.
One other downside to a wobble trap is the single spring setting. The practical result is that the low 1.5 m extreme targets do not make the 76 m distance without a stronger spring setting. That setting will put the higher targets well past the 76m stake. Probably, the best setting height is about 1.7m with the target landing short of the 76 m stake by about a meter or so. The higher targets will then pass the stake by about a meter or so. Depending on terrain, after experimentation, target setters may wish to set the lowest target to 1.7m.
It may be useful to know that the old late '60s, very early '70s ATA Modified Clay Pigeon Rules had the trap set at 2.9 meters height at 3.05 meters distance, with the target set for 65 meters; the target then was to vary from 1.2 to 3.35m in height and the angle was set for a maximum 45 degrees right and left of the straightaway. Interestingly, the rules did not specify an minimum angle. Also, the rules allowed the then UIT (now ISSF) 1 1/4 ounce shot load, but restricted the powder charge to 3 1/4 drams.
How it's played, US vs. ISSF versions: ATA wobble shooters usually shoot the discipline in the ATA standard format: 5 or 10 targets per station, then all move. ISSF (and the old ATA Modified Clay Pigeon Rules) shoots it like bunker: 6 person squads shoot and move as soon as the shooter to the right has shot his target – gun unloaded before turning from station 5 and not re-loaded until shooter is standing on station 1 (see ISSF rules). Note that wobble targets are shot from the 15m/16.4 yards (as measured from the front of the trap house per ISSF). Depending on the field layout, it may be advisable to be unloaded between stations, if the "fingers" are not safely flush with the ground and there is a chance of tripping, then safety requires guns to be unloaded when moving between stations 1 - 5. Of course, guns are always unloaded when moving between 5 to 1, as in all clay target games. . .
As a historical note, bunker has had the 76 meter distance for all targets only since the 24 gram era started in 1991. Used to be that the UIT distance was 75m +/- 5 m depending on the chart setting specification. The US had schemes in the 32 gram era where the 1.5 meter target was 70 m (less than a wobble will throw) with the maximum distance for other targets set to 75 meters.
Guns used: whatever is available if you're just enjoying or having an initial go. However, two shots is a requirement to get ready for bunker and it is necessary to learn to stay in the gun to break the target if you miss with the first shot and for chip shooting. Starting out, an automatic, or even a pump, will certainly do the job. But if you're serious about transitioning to bunker, then a perfectly fitting, perfectly balanced over-under is the only way to go. The POI will be dead-on for the second barrel and about 8" high for the first, although an argument can certainly be made for a dead-on first barrel for super-low improperly set targets.
On chokes, IM (0.025 to 0.028) and full (0.032 to 0.040) are a good initial choice, subject to final patterning check with your preferred ammunition. Shooting American trap loads of 1 1/8 oz, you can use chokes on the order of Lt Mod/IM without much penalty, especially with American targets.
Ammo used: anything available! 8's for the first, 7 1/2's for the second or 7 1/2's for both if you're more comfortable with that or prefer to simplify things. Heck, as Derek points out in his article "Up Tight On Choking", even a skeet load of 9's will get the job done for first barrel work on International targets. A Wal-Mart type 1 oz 1250'/s load works very well and is usually easily obtainable.
Shooting lens tints that work well for most shooters include brown, bronze and some reds in the lightest possible tint for the shooting conditions. Violet tint glasses work well with green backgrounds, but with high targets in a blue sky with large, white puffy clouds, a target can become difficult to see making second barrel shots undoable as the target appears to disappear in the cloud. The lens tint chosen must result in clear target contrast for you against the berm, the field and a partly cloudy sky. Having a yearly vision test and working with a shooting-experienced optician will go a long way toward maintaining maximum scores.
Final comments: Most clubs will not have International targets available. With a little negotiation, a club will often order them. It is worth noting that using American targets in place of the International makes wobble a different game. This is because the American target is lighter and larger. Therefore, it has to be thrown harder—the target exits the trap house faster—to make the 76 m distance. That makes it a bit more difficult to get a solid target lock. The American target also slows down faster, making second barrel leads slightly different (it's really apparent to International skeet shooters and will significantly affect doubles timing for them). Another difference is that the American target is significantly softer causing the target to break easier with only one or two well-placed (golden BB) pellets needed to get the job done.
Some feel that the difference in speed between the usual slow ATA/PITA wobble trap and a bunker makes wobble shooting poor practice. Once you are experienced at bunker, you will adjust to the speed difference with few problems. Probably this is so since trap shooters use swing-though to establish the lead with the target speed setting up the swing-through speed.
However, unless the practice wobble trap is using International targets and is set for 76 meters, the first few times on a bunker, shooters will experience and go through a significant learning curve before becoming used to the substantially faster target.
On foot positions: standard ATA should work very well. However, you will likely need to move your feet closer together, as the target should be at a much wider angle than ATA/PITA (45 degrees vs. perhaps 20 degrees. Probably the best personal test for proper foot position is to go to each station, mount the gun and move it along the line where an extreme target will travel. Adjust the foot position until you find that you are no longer being bound up and can move smoothly to the second barrel break point for each target without feeling restricted. As an example, here's a picture of Derek Partridge from his article You Can Shoot Int'l Trap and Skeet shooting a 45 degree target to give you an idea of the foot position and body movement needed to break those low angles.
See the following pics for suggested starting classic hold points for all five stations. Basically, they are (your) ATA hold points, but with the bead now at the trap house top, as opposed to the usual ATA hold, a foot or so high. If you are fortunate enough to have a wobble trap with the roof at ground level, the points will be at the front edge of the house. Note that left handers need to reverse the positions shown. Universal vision has to encompass the whole house with the eyes a few feet higher than the house—like bunker (see the discussion in tyro.html)—to pick up the target as soon as possible. In general, vision has to extend to ground to either side of house. The look point apex is about 2 - 3 feet above the roof, see the picture showing station 3 hold below.
Holding a high gun works for some shooters and seems to becoming more used. In a recent conversation with Derek Partridge, Mauro Perazzi confirmed that more and more of the world's top bunker shooters, as well as many Italian shooters—who are the world's best bunker shooters—have adopted the parallel-mounted, high hold.
For clarity on this point, here's a picture with Derek kindly demonstrating to show what it looks like to an observer. Note the barrel is held parallel to the ground, putting the hold point above the ATA house (or the bunker).
The hold is similar to the ATA/PITA high gun style where the barrel is held just below the target break point. In bunker this can work as well since the lowest legal target is still 1.5 meters (4'11") at the 10 meters measurement point and the target continues to rise.
Further examples can be seen by watching the ISSF World Cup shoot-off videos at www.youtube.com/issfchannel.
On barrel length, Derek comments: As most Italians are not particularly tall, they tend to favor a 75cm barrel length (which is 29.5”), while the British like 76cm because 30” is simpler than 29.5”! There is a growing tendency towards longer barrels, as they are smoother to swing to the fast bunker and wobble targets… providing the gun is still balanced on or very close to the hinge pin. These lengths include 80cm/31.5” and 81cm/32”, but never as long as the ATA 86cm/34”.
Station 1 classic starting hold point is around half way between left edge of the house and the center, with bead just below the front edge.
Station 2 suggested classic starting hold point is about at the center of the house, bead just below the front edge of the house.
Station 3 suggested classic hold point is half way between center and right edge, bead just below the front edge of the house (arrow). Look point is indicated by red circle.
Station 4 suggested classic starting hold point is at right edge of the house. If the target is improperly set very low, drop the bead to half the house height.
Station 5 suggested classic starting hold point is about 5 feet out from right edge of house, bead on a line with the top of house. This hold point is out from the house to insure the target doesn't beat you out: you may need to move further out. . . Test. Again, if target is improperly set very low, drop bead to one-half of house height to aid in target acquisition.
A very big thanx to Derek Partridge for his superb proofing skills and excellent suggestions.