I once fired a real AT4. I was in Army basic training on a cold December morning in 1995 at Fort Knox KY. I stepped up to the firing line, readied the weapon, took aim on a target tank, and let the rocket fly. For a split second the cold was gone and I was awash in heat. My vision was blurred with heat mirage. Then the tank was obscured by an explosion. Wow, that was cool.
The M136 AT4 is a light Antiarmor weapon currently used by the United States military. It replaced the M72 LAW (Light Antitank Weapon) in the late 1980s.The AT4 fires an unguided, fin-stabilized 84mm rocket with a high explosive anti armor warhead. This review is going to tell you how I built my Airsoft AT4. As far as I can tell, it's the first of its kind. I will not be going into details of its construction. This is not only for liability for Florida Airsoft, and myself but to get those who want an Airsoft AT4 to be creative. When I started this project I only had a few articles on the Internet, the supplies at the home improvement store, and my own creativity to go on. I would be interested in seeing how others would create an Airsoft AT4. Please e-mail me if you get a project started.
The idea for the airsoft AT4 was first found in a link on Arnie's Airsoft. The link was to an article by LT Macpherson on Airsoft BB grenades. The article proposes modifying a spent LAW rocket tube into an Airsoft LAW. In the article are links to information about Air cannons. The page I found most useful was titled "Not How To Build an Air Cannon" by Bill Mills. Bill uses his Air cannon to fire Paint balls among a host of other things.
With information in hand, I set off for the local home improvement store. There I purchased an array of PVC pipe, fittings, and the smallest electric water sprinkler valve I could find. Now I had to figure out how to make all this work. The first thing I discovered was that using a LAW tube would not work. The water sprinkler valve was too large to fit inside the tube. I would have to use something bigger. That would be an AT4.
Having never built an air cannon before, I thought it best to start with something similar to what Bill had on his web page. This would allow me to see what an air cannon can do and give me something to compare my AT4 air cannon to. Using air chambers and barrels as large as Bill's made for a cannon over six feet long. This of course is too long to fit inside an AT4 tube, so my next step was to figure out how much air chamber and how much barrel I could cut down and not loose too much performance. I also had to take into account that the solenoid for the water sprinkler valve would protrude from the AT4 tube. A few prototype barrels and air chambers later and I finally had some measurements I was happy with that would fit in the AT4.
With the air cannon installed in the AT4 tube, it was time to modify the trigger and striker assembly. The AT4's striker assembly was modified into a contact switch. A second switch was added which makes contact when the trigger is pressed and opens when pressure on the trigger is released. This setup allows all the AT4's original safeties to work as designed and makes for a more realistic replica. The two-switch set up insures power will only flow to the solenoid during firing, and added safety in the event of a switch malfunction.
All functioning parts finished, all that was left was for looks. A cap for the rear of the tube makes the AT4 look like an unfired tube while concealing the air chamber fill valve and batteries. The only part not authentic to the AT4 is a small box attached to the tube to cover the water sprinkler valve solenoid. I painted it to match the tube. This gave the AT4 a completed look.
How it fires
The AT4 is made ready by first removing the rear cap. Under the cap are the batteries for the water sprinkler valve solenoid and the fill valve for the air chamber. The air chamber is filled to 100 PSI with a compressor, and the rear cap is replaced. Next, the ammo round is placed in the barrel from the muzzle and pressed to the rear of the barrel. The AT4 is now loaded and ready for use.
To ready the AT4, first the shoulder stop is unsnapped and folded down, than the sights are released. The AT4 is now in the firing configuration. To fire the AT4, remove the safety pin at the rear. Next, move the cocking lever from the "safe" to the "cocked" position. Now the weapon is aimed. When on target, the safety is pushed and held down. The AT4 can now be fired by pressing the trigger with your thumb. If you can't remember all that don't worry, like other high tech military weapons, the instructions are printed on the side of the tube. All steps necessary to fire the real AT4 are also required to fire the airsoft version. Miss one of the safeties and it will not fire.
So far I have made three different types of ammo rounds for the AT4. All work off the principle of a sabot round which sheds the carrier part of the round once everything is up to speed and leaves the barrel. Then only the ammo part flies on to its target. The whole idea for this also came from information on Bill's page. The Three rounds are as follows:
1. Shot round with 600 BB load. This fires like a shotgun with a velocity of a little over 100 fps. Its range is 25 to 30 yards aiming with the AT4's sights. At 25 yards, its shot pattern is 30 feet wide.
2. Impact exploding round with 500 BB load. This fires a thin plastic bag of BB that ruptures the bag and ricochet around after hitting a hard surface. It's velocity is a little over 115 fps. It's range is about 25 yards using the AT4's sights.
3. Shot round with 300 BB load. Again a shotgun like round but with a velocity of over 150 fps. I've only fired two shots like this and haven't measured any distances or patterns for it yet.
So how well does it work? The psychological effect is great. Players on the other team run for cover. Everybody pays more attention to you while your team moves into position. People want to be on the team with the AT4. But how well does it work as an Airsoft weapon? In two games I haven't had a kill yet with it. It gets the other teams heads down. For a moment they have to get over what I call the "Holy Crap" factor. The AT4 goes off with a loud "Bang." Then comes the shower of BBs. One player it was fired upon described the experience as hearing the bang, then hearing what sounded like heavy rain hitting the building he was using as cover. All the firing I have done has been aimed with the sights. I feel that when I learn how much to hold over a target, the useful distance of the AT4 will be much better. Right now this weapon would be excellent on players out in the open. I can also say it has never misfire or malfunctioned in any way.
The Airsoft AT4 is an interesting one of a kind weapon. The real AT4 was never meant to be used against soldiers. It's an antiarmor weapon. But its fun to have for airsoft. It has its uses, and I feel that with a few improvements in ammo, it will do more. The new 300 BB shot rounds show much promise. A little more target practice and I'm sure I'll do better with it. Over all it's a lot of fun. That's what I got into airsoft for in the first place. I hope that if any of you ever see it fire you too will say, "Wow, that was cool!"
Review by: Skully.