Archive for September 2006
by B.B. Pelletier
Anics Skif A3000 is an attractive CO2 pistol. Holding 28 shots, it is the high-cap leader among pellet guns!
I was asked to report on this air pistol by one of our readers. I don’t think very much of the gun, and I’ll try to tell you why, but for the sake of the person(s) who might like to get one, I will also try to tell all its good features.
Right off the bat, the A3000 has the largest magazine capacity of any pellet pistol I know of, and also one of the largest BB magazine capacities. It shoots both BBs and pellets, which I will get into in a moment; but, with 28 shots on tap, it out-classes every other repeater on the market. The magazine is a transparent plastic stick affair with individual tubular pellet/BB holders running around like bumper cars on the inside. They follow an elongated track clockwise, until finally aligning with the barrel for firing. You load each chamber from the rear, then manually advance the tubes. Loading takes some time, but this is a double-action pistol that fires as fast as you can pull the trigger.
The magazine is unique. Twenty-eight separate plastic tubes move in a clockwise direction to bring either pellets or BBs (it doesn’t matter which) in line with the barrel, which snaps backwards to hit them and drive them back to open the valve. A bit like a nasty game of croquet.
Very good feel in the hand!
The Skif is also quite attractive, which is it’s strongest point after the magazine capacity. It’s just a real pleasure to hold. The rear sight is adjustable. And that’s pretty close to where the good points end.
A horrible trigger!
The double-action trigger-pull of 12 to 15 lbs. is about as bad as it gets. Not only do you have to advance those 28 plastic tubes inside the magazine each time you pull the trigger, but the way the gun works is that the barrel is also the hammer! It moves forward as the trigger is pulled until it finally slips off the sear. Under spring tension, it slams backwards into a hole in the magazine. The back of the barrel slams into a plastic tubular pellet holder and rams it backwards through another hole in the magazine into the firing valve, forcing it open. The pellet or BB is then pushed forward through the moving barrel by the force of the gas exhausting from the valve. It must have sounded neat to the drunken designers when they first thought of it at the fraternity kegger, but it works about as smoothly as a frozen caulking gun! It also has a single-action feature, but that sort of defeats the purpose of having 28 shots…no? However, the single-action trigger-pull is very nice, if a trifle heavy at just over 5 lbs.
Accuracy – schmakuracy!
As if a moving, spring-powered barrel were not enough to throw off all shots by itself, the Skif A3000 accommodates both BBs and pellets. The rifled barrel is one of those compromise-type affairs you’ve heard me talk about. No chance that anything emerging from the muzzle will go in any but a general direction! However, that’s not all. Those 28 plastic tubular pellet/BB holders in the magazine have to be small enough inside that a 0.173″ diameter steel BB will not fall out. To do that, guess what they do to the thin soft lead skirt of a pellet that starts out at 0.177″? That’s correct, they squash it down to fit! They even give you a little tool to poke the pellets into the tubes because they fit so tight.
Your chances of actually hitting what you aim at with a Skif A3000 increase with the size of your target. Pop cans at 20 feet are very possible. I was able to hold groups to 2″ at 30 feet when I shot single-action off a rest. However, who wants to cock the hammer manually every time when there are 28 shots aboard? In the double-action mode, the gun becomes a good noisemaker.
Your best chance for accuracy is to stand inside a weather balloon and shoot. You’re almost guaranteed to hit something.
I have laughed to read velocities quoted at over 500 f.p.s for this pistol. Maybe with BBs it goes that fast, but with regular lead pellets it’s in the 380-415 f.p.s. realm. That’s still cookin’ for a small pistol like the Skif, so feel grateful to get two full magazines of shots per CO2 powerlet.
This pistol is one you either will love or hate. Those who love it, enjoy the realism, the heft, the look and feel of the gun. Those who hate it are more focused on accuracy and shooting performance.
by B.B. Pelletier
Today, I’ll look at the shooting aspects of the BAM B40 underlever spring rifle. First, however, I want to tell you what I found with the trigger.
Adjusting the trigger
I removed the action from the stock to examine the trigger. It appears to be a copy of the Air Arms TX200 trigger but much cruder. The crosspins are so loose they fall out when the unit is turned sideways and bumped. I doubt this trigger can ever perform like a TX200 trigger without a major rebuild that would cost more than the price of the rifle. So, the question is, can it be used as is? For that, I tried to adjust it.
B40 trigger looks similar to a TX trigger, but the workmanship is poor. That results in a sloppy trigger engagement.
There are two adjustment screws, and they do have an effect on the trigger engagement, but nothing I tried gave me what I was after. What I wanted was a definite first and second stage, with a pause between them that could be discerned. I never got it. Instead, the best I was able to achieve after an hour of trial and error was a single-stage trigger with a very light pull and buckets of creep. I doubt it even goes 8 oz., but my trigger pull gauge doesn’t go down that far, so there is no way to tell for sure. My advice is to leave the safety on until you are ready to take the shot. It’s a shame that the Chinese were able to do so well with the rifle and then failed to get the trigger right. Maybe someone out there has learned the secret of how to adjust a B40 trigger, but I sure haven’t.
The B40 cocks a little harder than the TX, but just as smoothly. The anti-beartrap ratchet works in exactly the same way, catching near the end of the cocking stroke. And one quirk of both the TX and the B40 is that the trigger must intentionally be cocked during the cocking stroke. If the lever doesn’t come back far enough, the ratchet will hold the sliding chamber open and the gun will look like it’s cocked, but you will not be able to release the chamber to slide back forward. All you have to do is pull harder on the underlever and the trigger cocks and the safety sets.
Shooting is still just as smooth as a TX, and that’s after 75 shots on the powerplant. Some guns loosen up after several dozen pellets have run through, but this one doesn’t show signs of that yet.
After rereading my first post, I should have tested it with Gamo Magnum pointed pellets, but instead I tried it with Beeman Kodiaks and Crosman Premier 7.9-grain pellets. The Kodiaks gave an average velocity of 833 f.p.s. with a high of 841 and a low of 825. That’s a spread of just 16 feet per second over 10 shots, which is excellent for any spring rifle and unheard-of for a Chinese rifle. I am amazed by the power, too. The energy calculator on the Pyramyd website says that’s 16.34 foot-pounds of energy. By comparison, my well broken-in TX200 delivers an average velocity of 823 f.p.s. with the same Kodiaks. The spread was 23 f.p.s. and the muzzle energy was 15.95 foot-pounds. This is a result I never would have believed if I hadn’t seen it for myself!
In the B40, the light 7.9-grain Crosman Premiers gave an average of 909 f.p.s. with an extreme spread of 22 f.p.s. That’s a muzzle energy of 14.5 foot-pounds. The B40 goes against the common result of light pellets being more powerful than heavy pellets in a springer. My TX averages 933 f.p.s. with a spread of 19 f.p.s. and an energy of 15.27 foot-pounds. Apparently it also runs contrary to the norm with these two pellets.
The next report will be about accuracy. I have mounted a 3-9x Leapers scope on the B40, so both rifles are scoped equivalently. If this Chinese rifle continues to perform like it has, it will be a real airgun value and I will have to eat my words. I’m hoping that happens!
by B.B. Pelletier
Two things drove me to this posting today. We had a reader from Hawaii whose AirForce Condor is not performing as it should, and another reader named baldtrucker asked what happens when a multi-pmp pneumatic like a Benjamin 397 is over-pumped. I did a search and couldn’t find where I had addressed this question before; but, even if I have, it’s time to do it again.
How does an impact pneumatic valve work?
The most common valve is the impact type or knock-open valve, and that’s the one that has a problem with over-pressurization. When a hammer strikes the end of the valve stem of an impact valve, it forces it to momentarily lift the valve face off the valve seat. When that happens, air can flow through or past the valve stem and out into the breech of the airgun.
The valve face is held against the valve seat by a return spring. Also, any air pressure inside the reservoir where the valve face and seat are located pushes against the back of the valve face, forcing it against the valve seal. These two forces (the return spring and air pressure) are what keep the valve closed.
The hammer has to strike the valve stem with enough force to unseat the valve momentarily, allowing air to flow from the reservoir. The weight of the hammer and the strength of the spring that pushes it have been calculated to open the valve when the pressure inside is at its maximum. For most multi-pump guns made today, the valve allows all the stored air to be released. That’s easy because their reservoirs are very small. But, precharged pneumatic reservoirs are larger and only a portion of air is released. The next time the valve opens, the pressure inside (pushing against the valve face) is slightly lower, so the valve remains open slightly longer. A little longer flow of air at lower pressure is released, giving the same velocity to the pellet. This is always easier to control when the barrel is longer, so long-barrelled rifles are generally the most consistent, though a valve can be tuned for any barrel length.
What happens when a pneumatic is over-pressurized?
When the air pressure inside the reservoir is higher than the design of the action can accommodate, the hammer cannot open the valve as far as it should, so less air escapes. That is exactly what is happening to the Condor out in Hawaii. The Condor valve face is HUGE! It has to be, to allow as much air as possible to move through the valve. However, such a large surface area means the valve is also EXTREMELY sensitive to air pressure. Any over-pressurization will hold the valve shut, so the pellet gets very little air to push it.
When you put air into an airgun, it is nothing like putting gasoline into the tank of a car. Even then, more gas doesn’t make the car go faster, does it? What a pneumatic gun needs is air FLOW, and that happens only when the valve remains open as long as it was designed to.
Condors do not like to be filled to 3,000 psi. I have seen only a few that would tolerate it. Most like to be filled to around 2,800 psi. And I have seen a few that liked to be filled to just 2,600 psi. No matter what pressure you fill them to, as long as it is their maximum pressure, they will all give you about 20-25 VERY powerful shots when the power setting it set on high. That may seem counter-intuitive to some, but consider this: A NASCAR race is not won by putting more fuel into the car. It’s won by making the most of the fuel that is put into the car.
The same thing happens when a multi-pump is over-pumped. I hear stories all the time about how so-and-so pumped up his Sheridan Blue Streak 20 times, and it cracked like a .22. I just smile and keep my thoughts to myself, and now you know why. A gun that is supposed to be pumped a maximum of eight times isn’t going to crack like a firearm with 20 pumps. It isn’t going to do much of anything; and if it does, that gun is already worn out and powerless.
Crosman had the answer!
In the 1950s, Crosman came out with a pneumatic valve that couldn’t be over-pressurized – at least not easily. They put it in the Crosman 140 rifle and the 130 pistol and touted it as the answer to over-pressurization and valve lock, as this problem is commonly known. The valve did work as advertised, however, it had a few drawbacks. As the pressure increased, the trigger became harder to pull. It was impossible to fix that, and the triggers were always second-rate. This type of valve had the habit of opening on its own when the pressure was still low. I’ve had guns fire while I was filling them – so this valve type was not the solution to valve lock that it promised to be. They also had the problem of the pliable parts of the valve extruding through the valve ports under pressure.
So, that’s the story on valve lock. It’s pretty straightforward. As long as you operate your pneumatics within the parameters that they were designed to operate, they will serve both well and long.
by B.B. Pelletier
This post was requested by a reader named Michael.
Crosman Mark I is a great pistol to start with.
The LD is a specialized pistol modification for long-range air pistol shooting.
What is it?
The LD is a long-barrelled customized Crosman Mark I target pistol. It’s made by Mac-1 Airguns and has been around for more than a decade. It was designed primarily as a sillouhette gun, but it’s also used by many shooters who never compete. It has rifle-like accuracy and rifle-like bulk, without the length and weight of a rifle.
Over the years Mac-1, has offered guns with all sorts of barrel lengths, but they seem to have settled on a 13″ .22 caliber barrel. According to their website, they do not offer the gun in .177. The barrel is a German make, but not Lothar Walther. Rumor has it that they use Weihrauch barrels, but I can’t confirm that. It’s a heavy barrel and they re-contour the bolt probe for better gas flow. Readers of this blog should know by now that a CO2 gun gets its best velocity from a long barrel, so an increase of five inches over the factory length should offer a significant advantage. The designers of the LD have chosen to have more shots at a consistent velocity over raw power. Since they still get 75-100 f.p.s. higher than the factory Mark I, that’s a pretty good decision.
There are open sights, but this pistol is meant to be scoped. In fact, it uses a powerful rifle scope that is held up to the eye when shooting. A 3.5-oz. bulk CO2 tank hangs below the grip, giving enough gas for about 250 powerful shots, but it also serves as an anchor point for the pistol. The tank lowers the center of gravity, which offsets the large scope on top. It also cancels the weight of the long barrel. If you hold the tank against your chest, it steadies the gun. Your non-shooting hand grabs the rear of the scope and holds it to your eye in what looks and feels like a strange way to hold a pistol, but actually gives a very steady hold. The gun is painted black to match the dark barrel.
The gun weighs 61 oz. with an empty tank fitted. Add another 1-1.5 lbs. for a scope, and you can see this “pistol” is really a small carbine. That’s exactly what they intended it to be, and the weight helps you hold steady on target.
A great start!
They couldn’t have selected a better gun to start with than the Crosman Mark I. It already has a wonderful trigger and great balance. When they add their modifications, the gun just gets better. You can either supply your own Mark I or II for a discount, or you can just buy the entire gun all customized.
Powerful but not a magnum
The LD is set up to deliver its shots at 500 to 525 f.p.s. when shooting a 13.9-grain lead pellet. That’s not magnum power, but it is considerable. You can hunt with this airgun because it is a .22 and it’s accurate. Squirrels and rabbits out to 35 yards should be okay, and pigeons can be taken out as far as you can hold a 1″ group. RWS Meisterkugeln pellets are the recommended ammo out to 25 yards, but almost any quality pellet works well. I would use JSB Exacts for long-range shooting.
With all that power, the LD is really very quiet and docile. It doesn’t bark or kick because the gas use has been matched to the barrel. When the pellet leaves the muzzle, there isn’t an exhaust of white vapor that is often the case with unbalanced gas guns. The propulsive power of the gas is mostly expended pushing the pellet, leaving little pressure behind to go bang.
Accuracy is up in the rifle category. Once you learn the proper hold, you’ll be amazed at the accuracy you can achieve. I know shooters who can do very well at 50 yards with their LDs. I’ve never shot mine that far; but, at 35 yards, no target the size of a quarter was safe. The pistol retails for $395, if you buy it without a trade-in. That gets you the gun, two tanks and a refill adapter to fill from a bulk CO2 tank. Contact Mac-1 for further details.
by B.B. Pelletier
Several readers have asked for this posting, and one reader asked about lapping a barrel, which is supposed to be part of the rifling process. It has all but been abandoned by modern barrelmakers, at least those who make large volumes of barrels. Actually, the first person to request this post asked me to explain how BARRELS are made, but because that answer is included in this discussion, I included it within the talk about rifling.
Rifling was discovered very early in the history of gunmaking. In the beginning, the grooves ran straight down the bore, but soon they were made in a spiral pattern, and immediately gunmakers discovered that a spinning ball was more accurate. There are records of shooting matches in the mid-1500s, where rifled barrels were NOT permitted, because of the advantage they offered. So, the effect of a rifled barrel was known a long time ago.
Three types of rifling
There are three principal ways rifled barrels are made today, and two of them start with a long tube of metal. They are the cut-rifled barrel and the button-swaged barrel. The other – hammer forging – is quite different, so I’ll cover it by itself.
The following process refers to both cut-rifled barrels and button-swaged barrels. To get the long tube of metal needed for the barrel, the maker starts with a tube or a solid rod. Some small makers of airgun barrels start with a seamless hydraulic tube that they rifle. If they start with a solid rod, the hole through the center must first be drilled. The task of drilling a deep (long) hole through a solid rod of metal is one of the toughest machining tasks known. In World War II, the M1 Carbine was redesigned to eliminate one deep hole in the side of the receiver, because too many receivers had to be scrapped when the drill broke out of the side of the hole.
Many barrelmakers drill this hole on a lathe, but the precision barrelmaker uses a vertical axis machine to eliminate the effect of gravity on the long drill bit. The drill bit itself has a special cutting surface to reduce the tendency for the bit to wander. Even so, no hole is ever drilled entirely true. The barrel maker has to use other means to true up the hole if he wants a quality barrel.
The hole is reamed and (possibly) lapped
The next step is to ream the hole. A trueness of about 0.001″ along the axis is possible with very careful work. If the process is speeded up or the reamer is dull, it will be 0.0015″ or even 0.002″ of variation along the entire axis. If the maker is a good one, the next step is to lap the bore.
Lapping does not increase the dimension of the bore. It’s purpose is to remove the tooling marks left by the reamer, just as the reamer also removed the larger marks left by the drill bit. The finest lapping is done with a lead slug that is cast right in the bore of the gun, so the fit is perfect. The cooled slug is broken free and pushed halfway out the bore, where fine abrasive power and oil are brushed on. This is called charging the lap. I have read in many places that lapping doesn’t use abrasives at all, but rather it uses polishing compounds. Well, Virginia, polishing compounds ARE abrasives! They’re just very fine. If they weren’t abrasive, they wouldn’t work.
The charged lap is run up and down the bore, recharging as required to keep polishing the bore. Because the lap is lead, the lapping powder sinks into it before it scratches the steel bore, so this is a laborious process. It’s not unlike using J-B Non-Embedding Bore Compound to clean a leaded barrel!
After lapping, the barrel is cleaned. If it’s going to have cut rifling, it is now installed in a rifling jig or machine, which looks something like a lathe. A headstock holds one end of the barrel, which is held at the other end so that it can be turned easily. A rifling cutter is a very small tool that fits on the end of a rod long enough to pass completely through the barrel. The cutting rod is mounted on a fixture that causes the rod to spiral as it passes through the bore. Two hundred years ago, this fixture was a wooden positive of the rifling pattern desired. It had the same twist rate that was desired in the rifle. Today, a precision rotating fixture is used. Alternately, the barrel may be rotated and the cutting fixture held still, and the same result will happen.
When a cut is complete, the headstock is indexed for the next groove and another cut is made. When all the grooves have had one pass of the cutter, it is adjusted to cut deeper and another set of cuts is made. Each pass of the cutter will remove about one ten-thousandth of an inch, if the barrelmaker is a good one, so each thousandth of an inch takes ten full passes. If the rifling is 0.005″ deep, each groove took 50 passes of the cutter. If the barrel has six grooves, it took 300 passes of the cutter to completely rifle that bore. To speed things up, the cutter can be set to cut deeper, but that means more chances for burrs, gouges and associated tool marks.
Cut rifling has largely gone out of fashion today, though it’s still practiced. It does not result in a barrel that’s any better, but it does allow complete freedom over dimensions that button rifling does not allow. There is one more step after cutting the rifling, and it’s a final lapping. I will cover it after I describe button rifling in the next part.
by B.B. Pelletier
Today we begin our look at the BAM B40 underlever spring-piston air rifle. It’s a direct copy of the Air Arms TX200, and you know I think highly of it. This first part is a physical comparison between the two. The B40 comes in both .177 and .22 calibers, and I will test both for you. Because I own a .177 TX200, I will start there.
BAM B40 (bottom) is a close copy of the TX 200…at least in appearance.
This is the most beautiful Chinese air rifle I have seen! The stock is a hardwood stained to the light side of medium, and the contouring is nearly perfect. I found two spots where wood filler was used, but that is almost a trademark of Chinese woodwork. The thick black rubber buttpad is perfectly fitted. Even the two parts of the forearm that extend past the breech are nearly centered on the barrel and underlever mechanism.
This wood putty repair on the pistol grip of the B40 is about one inch long. It’s typical of all Chinese wood stocks – even the ones they consider high quality.
The stock differs from the one found on a TX200 in that is there is no checkering on the pistol grip or the forearm, and the forearm wood isn’t tapered to a slimmer profile. Also, the pistol grip isn’t quite as deeply scalloped as the one on the TX. As a result, the B40 stock feels slightly bulkier when held to the shoulder for firing.
The metal is polished, but not to the same extent as a TX. It is, however, up to the same standard as a Weihrauch rifle, which puts it light-years ahead of where Chinese rifles used to be. The triggerguard is dull but evenly black, and the trigger blade is well-formed.
Breech not finished as well
When I cocked the gun, the sliding compression chamber slid back to reveal a cone-shaped breech with some tool marks. The squared-off TX breech is perfect, by comparison. Cocking effort is slightly higher (a pound or two at most), but my TX has thousands of shots on it and this is a brand-new action, so I’ll cut it some slack. Cocking is just as smooth as the TX, and the anti-beartrap ratchet that holds open the sliding compression chamber is just as crisp as the one on the TX. The underlever lock (a ball bearing) has been exactly replicated on the B40 and works fine.
When you scrutinize the work it comes apart, like these tool marks left on the breech.
Very smooth shooting
I’d heard a comment that the B40 had lots of spring noise and vibration, but that isn’t the case with the one I’m testing. It shoots just as smoothly as a TX200, which says a lot. The TX shoots like a tuned gun right out of the box, and I’m saying that the B40 does, too. It’s also just as quiet as a TX, which means the baffles in the barrel shroud are just as effective.
Trigger light but mushy
The two-stage trigger is a copy of the TX trigger, which in turn is a close approximation of the famous Rekord trigger that Weihrauch has used for five decades. The release is very light, but, like I commented about the BAM B26 trigger, the first stage is mushy and the second stage is imprecise. I can get used to it, but it’s a far cry from a TX trigger. I hope I can do something about it before I go to the range for accuracy testing.
From the firing behavior, I suspect the rifle will shoot either in the high 800s or the low 900s with the Gamo Magnum pointed pellets I used to check firing behavior. If that’s true, I would expect to get the best accuracy from either Beeman Kodiaks or JSB Exact domed heavy pellets.
We’ll find out in the next test!
by B.B. Pelletier
Today, we’ll talk about triggers. Besides the sights, the trigger is the most important part of a target airgun. On a pistol, the trigger is just as important as the sights, because the proper use of the trigger promotes stability and control over the handgun.
How light should a trigger be?
Many veteran shooters like their triggers to be as light as they can be, commensurate with safety. Indeed, on world-class 10-meter target rifles, the trigger-pulls can be adjusted to mere tens of grams. But, a light trigger is not good for the beginning shooter for a number of reasons, with safety being the overriding one. By the way, the guns are called 10-meter guns because the targets we shoot are 10 meters, or just under 33 feet, distant. That distance is measured from the muzzle of the gun – both rifle and pistol.
The types of target rifles that are intended for training shooters have heavy (for competiton guns) trigger-pulls. Crosman’s Challenger 2000, for example, has a two-stage trigger that breaks at 3 lbs. Daisy’s Avanti 853, which has been around for decades, has a single-stage 6-lb. trigger! Neither one is adjustable. Both companies have learned the hard way that new shooters, and some who should know better, are not cautious about the trigger, so they make their triggers on the heavy side. This is perfect for the beginner. By the time they know exactly what they want in a trigger, the safety procedures will be deeply ingrained.
Watch each new shooter!
An instructor faces the moment of truth every time a new shooter touches a gun. The most dangerous part of the gun is the muzzle; however, at the same time, the instructor must watch how the shooter addresses the trigger. I have some friends who instinctively put their trigger fingers on the trigger of a gun every time they pick one up. These are dangerous people! If memory serves me, every one of them has had at least one shooting accident. Do not allow new shooters to get into the bad habit of touching the trigger before they’re ready to take the shot. Make them hold their trigger finger straight out alongside the triggerguard until the proper command is given to shoot.
The RIGHT (and only) way to squeeze a trigger!
There is just one way to squeeze a trigger to obtain the best accuracy. I will describe rifles first, and then pistols. First, get into your position so the rifle is fairly close to the intended target. Then take a deep cleansing breath and let it out. Next, breathe deep and let about half out. You now have five seconds or less to sight and squeeze off the shot. Align the sights and take up the first stage. This is where a single-stage trigger becomes a liability. When the second stage is reached, squeeze with increasing pressure while keeping the sights aligned with the target. If you go longer than five seconds, relax and begin again. If all you have is a single-stage trigger, pretend it is the second stage of a two-stage trigger. The reason for the five-second limit is that after that time, your muscles will start twitching and throwing you slightly off target. If you watch a champion shooter, they get the shot off in three seconds or less.
The shot should come as a surprise. Keep practicing until it does. If you intentionally make the shot go off, you will move the gun, however slight, and that’s called “flinching.” At this point, you’ll also understand the necessity of an overtravel adjustment. It makes the trigger that much more precise. When you have done this a thousand times, you will get a feel for your trigger and how it has to be manipulated.
Trigger work with the pistol
First, get into your stance. Raise the pistol with your eyes closed, and the sights should be on the bullseye when you open your eyes again. If not, move your feet until they are. I like to point both toes slightly inward to put tension on my legs; it gives a more solid stance. Then, you’re ready to shoot. Rest the loaded pistol on the shooting table and take a cleansing breath. Take another breath and let half out as you raise the pistol and drop it back until the sights are aligned with the target. This starts your five seconds. Squeeze the first stage out and begin the second stage. Increase pressure until the pistol fires. If you take too long, release the trigger and start over.
After the student has fired many shots and about five times as many dry-fire shots using exactly the same technique, they will be proficient with that trigger.