A NEW BENCHREST TRIGGER By Roland Paolucci © 2006 There is a new triggerman in town. No, you don’t have to call the police or Homeland Security - he’s not that kind of triggerman. After several months of development, Kelbly’s Inc., manufacturer of the Stolle line of benchrest actions, has begun producing a new benchrest trigger of George Kelbly’s design. As one might expect, it is a three-lever trigger. Among its unique features is the ability to change the weight of pull without adjusting screws or changing springs. But more on this later.

This move into the trigger market should not come as a complete surprise to those of you who have been involved in benchrest competition. The Kelbly family has been constantly adding items to their catalog of products. They began in 1981 with the production of Ralph Stolle’s eminently successful aluminum-body actions. Soon after, they began making aluminum scope rings. They added the first of three Mazak CNC machines in 1987. In 1999, with son Michael Kelbly in charge, they started producing graphite/fiberglass stocks, some in their own design. In the April 2001 issue of PS this author wrote about the introduction of their stainless Grizzly II action and, at the same time, the production of the Stolle Swindlehurst rimfire action. They will make the Grizzly II in chrome moly on request, but that is another story. There are reasons for Kelbly to enter the trigger market at this time. Frankly, they were finding that customers were buying their Stolle action, putting on one of the several benchrest triggers available, and finding that the rifle would not shoot reliably. “This is bad for our business so we have had to do something about it.” After analyzing the situation, Kelbly came to the conclusion that the problem was most frequently caused by too little fall (travel) of the firing pin. “Other triggers are advertised as Remington replacements but the problem is that they have a fall that is 40 to 100 thousandths shorter than a Remington and rifles often won’t shoot right with them. A Remington-style trigger should have close to 260 thousandths of fall. If it doesn’t, the rifle usually won’t shoot consistently from shot to shot. We have had to make four or five different brackets to accommodate these triggers so that the rifle will shoot. It’s amazing how many triggers we’ve worked on and made a sick gun well. I know that we’ve done several hundred of them.” For the past two or three years, when a customer bought a complete gun from Kelbly, the trigger was worked on. Often, in addition to the too short length of fall, internal parts had burrs, were galling, or there was a problem with porosity of the casting. “I have been at matches when someone’s gun stopped shooting and I’ve had my stuff for working on triggers with me. It happened to Larry Engelbrecht. He’s an engineer for Cessna and had a Grizzly II that had not been shooting consistently. I told him to let me work on his trigger. Larry said working on the trigger is not going to do anything. I said let me work on it. I worked on the trigger and when he returned from the next relay he said, ‘George, you could have told me the rest of your life that you could change the way that my gun shot by working on the trigger and I would never have believed you.’ Now it’s shooting bug-holes.” When asked about when he got the idea for this trigger, George replied, “Thursday May 12th, 2005 in the morning.” I wasn’t expecting that specific an answer, so all that I could think to jokingly ask was, “What time?” Kelbly said that he had been thinking about it for a while but he woke up on the 12th of May with an idea for a solid case three-lever trigger with no side plate and with a pin going from the sear bar through the case to the third lever. It was all he could think about all day and the next afternoon he went into his office and shut the door, and, in an hour, drew up the design for the prototype. “On Monday morning I ordered the parts to make it and by the end of the week I had the first one done.” This prototype had an eleven-ounce pull and that was as light as Kelbly could make it. Two days later, with slight modification, the second trigger was done. Kelbly used it at the Super Shoot and continues to use it. “It is a very good two-ounce trigger but I have been able to improve on it some more.” HOW IT WORKS The body is machined from a solid block with no need for a cover plate. When asked about it, Kelbly said, “ I wanted a solid case. That way there can be no warped side plates or dings inside to interfere with the mechanism operating properly.” It is generally accepted that if one wants a precision 2 oz. trigger, it will have three levers. As mentioned above, the Kelbly trigger has a third lever. However, its placement in the mechanism is unique. George places the third lever near the bottom of the trigger instead of up under the sear bar, where it is usually found. Kelbly has placed a pin under the sear bar that is tripped by the third lever. (See picture No. 1). His original plan had only one hole for the pin. Kelbly realized that he could increase the flexibility of the trigger by adding three more holes to allow a change in the pin position. By positioning the pin in the next hole, the point of contact with the sear bar changes, increasing the pressure needed to trip the sear. The net result is that moving the pin to the second hole produced a 6 to 7 oz. pull. The third and fourth holes produced pulls of 10 and 16 ounces, respectively. As a very desirable side effect, each time the weight of pull increases, the lock time gets shorter. This is because as one moves the pin to the 2nd, 3rd, or 4th hole, the new pin placement causes the third lever to move progressively less and less, shortening the lock time. A WORD ABOUT LOCK TIME Most folks think of lock time as a single entity, the length of time it takes the firing pin to fall when the cocking piece is tripped. If you think about it, this is only half of the equation. The trigger has to do its job first. If the internals of a trigger have to move a lot before tripping, this delay will slow down the total time, even if the bolt/firing pin assembly itself is very efficient. You may think that a few thousandths additional movement is insignificant but fall time is measured in milliseconds. Kelbly says that in hole #4, his third lever moves only about 30 thousandths, whereas two of the most commonly used benchrest triggers have movement of around 300 thousandths. George says “Our trigger is the only trigger that can alter lock time without remanufacturing parts or changing springs.” Kelby holds a patent for his design. It is a simple operation to move the pin to another hole. Remove the trigger from the action, push out the rear pin, swing the sear bar up, and turn the trigger assembly over, giving it a tap on an appropriate surface. The small pin will drop out. Simply place it in the desired hole, and replace the trigger in the rifle. No words of caution needed. No parts or springs will come flying out. (I’m reminded of all those times on my hands and knees with a magnet, trying to find a tiny part that flew out of the whatever-it-was!) HOW THE TRIGGER IS MADE Kelbly decided that if they were going to make these triggers, and have a number of variations, the fastest and most economical way would be by using a water-jet cutter. So he ordered one. “The delivery was only twelve weeks late and the pump I got with it gave us a lot of headaches and wasted another six weeks. Now, after a lot of time and money, I’ve got one that works.” The manufacturer, WARDJet™, tested it for positioning with a laser and reported that it was the most accurate water-cutter they have built. Kelbly is hopeful that they will be able to do other jobs with it, possibly scope rings. “I’ve got ideas for a whole variety of trigger shoes. Round or straight - with this machine I can make them in a few days. And we’d be able to position the shoe exactly where you want it. We’d just have George Jr. change the program and cut them out. Our trigger piece, which has the most complicated shape of all the parts, takes all of two minutes to make on the water cutter, and the body itself, including the holes, takes only seven minutes plus another twenty on the Mazak. When finished, the holes are slightly undersized and have to be reamed.” The completed trigger case will have a coating applied and will have a coefficient of friction that, according to Kelbly, is about as low as possible to achieve, with a minimum surface hardness of 72 Rockwell. Up until now we have been discussing benchrest-style triggers, triggers that are most commonly set in ounces. It is expected that the four-hole/pin arrangement will probably cover most of the shooting and hunting needs without adjusting any springs. For disciplines that require heavier pulls, such as two lbs. or more, a heavier spring can be installed and adjusted. “One can change the pull weight by changing the trigger shoe return spring. I understand that some shooting disciplines in Japan have a one-kilo requirement. At that setting, our trigger will have an incredibly fast lock time.” Kelbly does not recommend any change to the 3rd lever return spring. “ For my personal use, I prefer to have a trigger adjusted to three or four ounces. I shot smallbore when they had a three-pound rule. When they dropped it, we all lightened our triggers to a few ounces – we couldn’t hit the side of a barn. So we set them back. We found that they had to be at least a pound and a half before we could shoot the scores we had at three pounds.” TESTING Kelbly has done a lot of trigger testing using some sophisticated equipment. Greg Walley, who does most of the chambering at Kelbly’s, made a computer-integrated device that can accurately measure the time from trigger pull to the start of the cocking-piece fall. He devised a means to electronically measure the mechanical actuation of the trigger mechanism with the accuracy of plus or minus 2%. This is done with a customized high-speed digital data acquisition system, interfaced to fiber optic and inductive sensors. With it, he is not only able to time the mechanical movement in the trigger mechanism, but also the entire ignition system of the rifle from the trigger sear to the tip of the firing pin. Greg says, “This will allow me to diagnose nagging ignition problems (e.g. drag) that would otherwise be difficult or impossible to detect during the firing sequence.” While testing other benchrest and target triggers, they discovered that few that claimed to be 2 oz. or less had lived up to their claim. George Sr. has been frequently asked why the Kelbly trigger feels lighter than the other 2 oz. triggers. He usually just smiles and says that some 2 oz. triggers are 2 oz., and some are not. Kelbly measures trigger pull of every trigger with an Imada Digital Force Gauge, a $700.00 precision device. It should be understood that the data in the attached graphs was obtained from a very limited sample and in some cases was obtained by testing the only sample of a particular trigger that was at hand. Neither Kelbly Inc. acknowledges that the results from a larger sample might alter the results slightly but not significantly. Greg Walley has asked me to include the following statement. “ Due to the nature of the sensor placement between testing setups, hysteresis in calibration, and individual dispersion of characteristics between the triggers respective moving parts, the accuracy of the actual measured values (time in µS along the y-axis) can vary up to 10%. However, the precision of the consistency of the measurements (slope values along the x-axis and standard deviation calculations) for each individual trigger is within 2%.” Greg will offer a diagnostics service in the near future using his lock time analysis system to troubleshoot ignition problems in the firing mechanism of rifles. He will be able to detect and isolate potential problems in the trigger, firing-pin assembly, and bolts of customer’s rifles. Check with Kelbly’s Inc. for further details. Kelbly’s Inc. 7222 Dalton Fox Lake Road N. Lawrence, Ohio 44666 330-683-4674 FAX 330-682-7349