Here is an article I wrote which was published in The Trapper and Predator Caller magazine pertaining to adjusting large conibears. The purpose of this adjustment is to eliminate or drastically reduce the number of otters and beavers caught by the hind quarters in large body grip traps.
As I approached a very productive beaver set one drizzly January day a couple of years ago, I noticed the set area was torn up a great deal. Once at the set, I saw where a long struggle had taken place. All that remained was an empty #330 body grip. The set consisted of a #330 placed in a well-worn channel below a beaver dam. This channel connected two beaver ponds and was a hot location. Upon closer inspection, I saw the unmistakable tracks of an otter in the soft mud on a nearby bank made during its struggle. This set had been the best producer at this site, accounting for several beavers.
During the process of resetting the trap, I remembered that this specific trap had caught two otters earlier in the season, and I remembered that both otters were caught far back on their bodies, just in front of the hind legs. I was able to recall with certainty the history of this specific trap because a spring had broken on it a month and a half earlier, and I had to replace that spring. When I replaced the spring, it no safety catch, because it was lost when the spring broke. I had no replacement safety catches, so I fashioned one out of a piece of small-diameter rod. This homemade safety catch was different in diameter and length than the factory catch, and it stood out.
I decided to pull this body grip, take it home and try to determine why it was performing so poorly on otters. I had another #330 nearby that was not producing nearly as well, so I moved it into the better location where I had lost the otter.
Once home, I inspected the trap and found that it appeared to be in very good shape. The jaw rivets looked good, the jaws weren't bent, the springs were plenty strong, the dog looked good and so did the trigger. I was baffled.
Next I tried a function test. I compressed the springs and put on the safety catches. While squeezing the jaws together with the dog and trigger on top, I rested the bottom jaws on my workbench. I pulled the springs down so they were in contact with the bench, which caused the safety catches to slide down and stay fully engaged with the springs. While grasping the upper jaws on the set body grip, I used a wooden stake to push on the trigger. Right away I noticed that the trigger had six to eight inches of play. Once I encountered resistance, I kept pushing the trigger with the stake. To my amazement, the triggers moved in an arc to almost a parallel position to the bench before the trap fired. (The trap didn't completely fire because I still was holding the jaws with my hand.)
Now I knew why the otters were getting so far through the trap before it fired. I also was having some trouble with catching beavers farther back on the body. I've had other incidents where I had poor holds on otters in other traps, but I didn't know which traps they were. After my discovery, I inspected all of my #330s and #280s right away.
In the past, I had attributed poor holds on otters to the animals' remarkable swimming speed. I thought they were simply torpedoing through the trap before the trap could fire to get a decent hold. I also thought the poor holds resulted from otters' ability to slither around trigger wires. I had experimented with the different types of bends in the trigger wires and even put a wire between the ends of the trigger wires, to make it impossible for an otter to slither around the trigger. While this improved the holds to some extent, I was still having too many holds way back on the otter. Now I knew why.
I knew the key to correcting the problem
was in the dog and trigger, so I examined them closely. I found the
play in the trigger was because the dog didn't seat all of the way into
trigger notch. The trigger moved freely because the flats of the dog
contact with the bottom of the trigger notch (See Figure A).
To reduce the play, use a round file to
deepen the grove in the dog (See Figure B). File just enough metal away
allow the flats of the dog to come in contact with the bottom of the
notch (See Figure C). This eliminates
the play in the trigger. Because the dog groove is deeper, the dog has
farther upward to disengage from the jaw. This causes the trigger to
travel even farther before the trap fires.
To correct the excessive trigger travel, its necessary to do some more filing. Using a flat file, make a bevel on the forward side of the dog groove (See Figure B). This will cause the dog to have to move less to disengage from the jaw. File a little at a time, testing the travel of the trigger frequently. Ideally, I like to have the trigger move about one to two inches for the trap to fire. This does not cause a hair trigger because it still takes the same amount of pressure to move the triggers, but they don't have to travel as far.
For this adjustment to be the most effective, I recommend the bolt-on or riveted type triggers be used. I've found that the four-way triggers are very difficult to get consistent results from while using these adjustment procedures. All of my body grips were adjusted as described above, and all but one of the otters I caught last winter were held from just behind the head to the front shoulders except for one. This one exception was caught in a #330 that had the four-way trigger installed, and the otter was caught just in front of the hind legs.
I've found this condition primarily on older, used body grips, but have had to adjust some new ones. I haven't had any experience yet with the Species Specific type of body grip, so I can't say how the trigger travel is on it.
It's a good idea to check all of the larger body grips for excessive trigger travel and adjust accordingly. I hate to lose an otter when I know I could have prevented it. I don't plan to lose any more otters to traps out of adjustment.