M203 Style grenade launchers

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Few things in life are more fun than popping off a LAW rocket from an M203 Grenade Launcher. Always ready at a moment's notice the M203 style airsoft launcher offers an alternative to the same old PVC and pipe style rocket launchers. Photo provided by PaintballPhotography.com

Sometimes during a scenario game the difference between success and failure is determined by a single, well placed, football shaped piece of foam with fins on it.  Of course I’m talking about scenario LAWs (also known as rocket launchers) and the little Nerf Vortex rounds that they fire.  While most players will use a collection of metal pipes and PVC, there is another way of firing these little neon orbs of destruction…the airsoft based M203 style Grenade Launcher.

Why an M203?

If you’ve played scenario paintball for long enough you’ve been in a situation where you wish you had the ability to take out a large group of players all at once.  Maybe they are all clustered behind a rock or stacked up in a building.  Usually they are in a key position that dominates a certain area of the field and so long as they are there your team is stuck.   Or maybe it’s even worse than that.  Maybe they are in a tank.  Now not only are they all clustered behind cover but they are mobile and can fire from cover. 

For most scenario players, this is a job for a LAW. They put down their marker, un-sling the LAW from their back, grab some cover where they might be able to get a quick snap shot off, pop out, and yank that ball valve handle for all it’s worth hoping they did it quick enough to get a good shot off.

There are a number of problems with this setup though.  First, the shooter has to drop his marker to use the LAW.  In a situation where every gun matters, this could be detrimental.  Also a great shooting position may not be the best spot for a LAW shot.  Thus the LAW player may need to move to a better position where he can get his LAW on target while still having appropriate cover.  Of course there is also the time factor.  The longer it takes to get that LAW into action the greater the chance of the LAW player being shot out or the target moving on out of the LAW’s range.  You also have to make sure that the lever for the ball valve style LAW, which most LAWs use a ball valve for a trigger, is opened at the same rate every time to make sure each shot is fired with the same velocity as every other shot.  Lastly, it is easy for the other team to pick out your LAW guys as they will be the ones with the big 2.5” PVC tube on their back.  That makes them inviting targets.

Okay, so I really do not paint a great picture of the LAW player’s life and generally speaking it is not easy to effectively use a LAW without getting taken out quickly shortly thereafter.  While I have seen some LAWs that address some of these issues, including one LAW that was only slightly larger than a pistol, almost every single one has the drawback of the player using it no longer having the ability to fire his marker while doing so.  With that in mind many players have turned to their airsoft brethren and started adapting airsoft M203 grenade launchers for use as rocket launchers.

Airsoft M203 Considerations

For those that don’t know what an M203 style launcher is let me give you a definition.  The M203 grenade launcher, the real one, was designed to replace the M79 grenade launcher used in Vietnam.  The M79 fired a 40mm grenade round out of  a tube and allowed infantrymen to lob grenade rounds a lot further than they could throw them yet the launcher was smaller, more portable, and quicker to bring into action than a infantry mortar.  However, the infantryman who used the M79 could not use his rifle while using the grenade launcher thus decreasing the unit’s rifle firepower.  So the military developed the M203. 

The Classic Army M203 mounted on the underside of my MilTec MT-66 marker. This is a R.I.S. mounted "long" style M203. The "Short" style has a 3" shorter barrel. While it will work, the shorter barrel isn't the best option for firing Nerf rounds. Note the two thumb screws that hold the launcher to the rail system. Also, the trigger gaurd for the launcher slips to the magazine well of the marker. If you don't have an M4 style marker you can push the gaurd further up to attach to the launcher itself. It makes for a smaller trigger but you don't want to accidentally discharge a launcher!

The M203 fired the exact same rounds as the M79 but it mounted under the barrel of the standard rifleman’s M16 rifle. This launcher could be brought to bear even quicker than the M79 since it was always “at the ready” and the rifleman didn’t have to sacrifice the use of his M16 to fire a grenade. 

In paintball, we have the same issues with LAWs and the M203 style launchers have similar benefits as their real world counterparts.  Being mounted on the marker, the launcher is always available and can be used anytime the player needs it.  It also takes less time to be fired at a target because the player doesn’t have to switch out weapons to deploy it. 

However, everything comes with a price.  First and foremost for the paintball player is whether or not they can use an airsoft M203.  There are two styles, the standard barrel mount M203 and the R.I.S. mounted M203.  The barrel mount style will not work with any paintball marker because our barrels are so much larger in diameter than their airsoft counterparts.  This leaves us with the R.I.S. mounted launchers.  All these launchers need is a Picatinny style mount about 3” long on the underside of the barrel.  Obviously if the player’s marker doesn’t have such an option or the option isn’t available for their marker then an M203 style launcher is out of the question.  However, any MilSim style marker or those markers that do have Picatinny rails on their underside would be able to use the M203.

So let’s assume you can mount an M203 to your marker. Next is cost.  You see, the launcher itself is pretty simple and basic…which is to say it doesn’t do much on it’s own.  What does the real work with an M203 launcher is the shell.  That’s right, these things actually have shells.  Hey, no one ever said that airsoft players weren’t about realism.  While there are a ton of shells for the airsoft community for us paintballers the main shell we use is the Mad Bull XM-PB4.  This shell has a couple features that make it ideal for paintball. 

First, it can be ran off CO2.  Normally these shells run on what is called Green gas or Red gas.  Suffice to say that these gases (really propane gas) have a max pressure of about 200 psi.  Since for paintball we want to fire a Nerf round 200 psi in one of these shells just isn’t going to work.  You can throw a Nerf round further than an M203 at 200 psi.  Thus you need a shell designed to work with CO2 so that you can fill it at a higher pressure. 

If you're using CO2 (and if you plan on shooting Nerfs you're going to be using CO2) then you'll need this. To the left of the gauge is the CO2 fill adaptor. The needle goes into a valve in the back of the grenade. The section with the knob and gauge is the regulator. The knob controls the pressure going into the grenade. To the left of the gauge is the 12 Gram adaptor. This is optional. The regulator can screw onto any air tank that is used for paintball.

This also means you will need a CO2 adaptor that will fill the shell.  They make two, one with a regulator and one without.  Now, as we all know unregulated CO2 can be as high as 1200 psi!  These shells are not designed to work with those pressures.  So why they even make a non-regulated CO2 adaptor for these shells is beyond me.  Thus you NEED to get the one with a regulator.

So what’s the big deal you ask?  Cost.  Airsoft M203 setups are not for the faint of heart or thin of wallet.  The launchers can be bought for under $100 if you know where to look (www.ebaybanned.com and type “M203” in the search bar).  The shells run about $80 EACH and the regulator/adaptor is another $70.  So just to get the basics you are looking at about $250 plus shipping, tax, etc. 

The good news is that the shells are reusable and you can refill them on the field so you can get by with just one shell to start with but you can see if you want to get more shells (I have three) it’s going to cost you.  So if you don’t have a lot of money, an M203 setup may not be for you as a traditional LAW can be set up for much cheaper. 

Just like with your marker, be sure to get a Barrel cover for you launcher as well! With a 2" barrel diameter it won't be easy but most feilds require you have one.

Operational Pros and Cons to the M203

So if your marker can mount the M203 and you’re not scared away by the cost what’s next?  Well, there are some operational issues to contend when using the M203.  First, while it is quicker to get off the first shot with an M203 follow up shots are going to take more time.  The reason is you have to deal with those shells.  Now, if you have more than one shell this will help as you can drop out the expended shell and just put in a fresh one.  At $80 each though you don’t just want to leave them laying around like a $2 paint pod and you may only have one shell.  This means you have to reset the valve and refill the shell as well as load another Nerf round and the shell.  Having done this I can tell you that this takes a long time and is not as quick as just shoving a Nerf round down the muzzle of a traditional LAW launcher. This may be an issue for you depending on your budget and the rules at your field regarding Nerf hits.

Drawing of the Mad Bull XM-PB4 paintball grenade shell. Image from www.madbullairsoft.com

The other issue is weight.  The launcher itself weighs 3 lbs and the grenade round weighs another pound for a total loaded weight of 4 lbs.  This is more than some markers weigh!  Not only this, it is all focused on the front end of the marker.  If you carry more than one grenade round that weight adds up too.  So if you like to run a light setup an M203 may not be for you either.

There are a couple other issues to address with these launchers.  First is the barrel size.  It is 40mm or about 2” in diameter.  The Nerf rounds used for LAWs are 2.5” in diameter.  Luckily for us they are foam.  These can be squished down and fit into the barrel fairly easily.  With a very simple modification that we’ll talk about later, the problem goes away completely and the Nerf rounds can be breach loaded rather than muzzle loaded.

Secondly is the shell itself.  The Mad Bull XM-PB4 (which is the same as the RAP4 Thunder Grenade many paintballers are familiar with…RAP4 gets those shells from Mad Bull) is designed to fire four .68 cal paintballs at about 300 psi. (Note it is said that you can also use this as a "smoke grenade" but unless you like cleaning baby powder off your marker and launcher I wouldn't recommend it.)  The shell will take up to 400 psi of pressure for Nerf rounds without any major issues.  However, the range on a Nerf round fired at 400 psi is only marginally better than one fired at 200 psi and certainly doesn’t match the range of a regular LAW.  To get that kind of range the pressure needs to be about 700 psi!  Stock the shells will not tolerate this kind of pressure for long but, like with the Nerf, there is a solution as we will talk about…well…now.

Correcting the Shortcomings of the Airsoft M203

First we’ll address the problem with the shell.  To understand the problem you need to understand how the shell fires.  Below is an animation of the firing and valve reset process of the Mad Bull XM-PB4:

Animation of the Mad Bull XM-PB4 Grenade

Now the problem is that the valve body (blue) is made of aluminum.  The ball bearings (light green) are hardened steel.  When the valve body slides back it strikes the base of the shell base (black).  Under high pressures it strikes it VERY hard.  Something has to give and in this case it's not going to be the hardened steel bearings or the thick aluminum shell body. Over time, the valve body will warp. At very high pressures, such as say...700+ psi...you'll only get about five to ten shots before this happens. When this happens, you will not be able to reset the valve and thus the grenade will not hold an air charge.  Obviously this is bad.

Luckily the fix is fairly easy.  What we are going to do is give the valve body something soft and squishy to bump up against rather than that nasty, hard grenade body.  This will be our new Grenade Valve Buffer.  You’ll need a hobby knife and a thick Spyder striker buffer. Now, there are two different Spyder striker buffers…a thin one and a thick one:

This is the thin Spyder striker buffer. This is what you DON'T want! If you can't find anything else, it will do but the outside diameter of this buffer is a little small and will not work as well as the buffer pictured at right. This is from the Warsensor WS66 teardown so please excuse the "Step 17" tag. This is the thick Spyder striker buffer. Note how much wider it is than the one shown at left.

You need the thick one on the right. Now, taking the X-acto knife you are going to “slice” the buffer into thirds.  You only need one of these so if you only want to cut off one piece that’s fine too.  You want to make the thickness of these pieces as uniform as possible.

Once you have that piece cut we will need to make it fit on the button that fires the grenade (orange in the animation).  If you look at that button you’ll notice that it has kind of an “I” shape to it (if you were to stand the button upright, of course).  We want the new Grenade Valve Buffer to slide easily up and down the body of the “I” but not be able to slide over the stops at each end.  Using the X-acto knife (but a reamer like a Uni-bit would be much better here) begin to enlarge the hole in the center of the Grenade Valve Buffer.  Enlarge it slowly and keep test fitting it over the button often until it will slide up and down on the button body without having to be forced. 

When you have finished and have reassembled the grenade, the Grenade Valve Buffer will sit like in the following images (the buffer is in red):

Mad Bull XM-PB4 prepared to fire with Grenade Valve Buffer in place (Marked in Red)
Mad Bull XM-PB4 during the firing process with Grenade Valve Buffer in place (Marked in Red)

You can even put a little oil on the button to help the assembly move smoother. 

With that done overcoming the issue with the Nerf rounds is easy.  Using black electrical tape, slowly start wrapping the body of the Vortex round starting at the nose and working your way towards the rear of the “football” part of the round making sure to overlap the wraps by about an eighth of an inch.  While wrapping, you are going to want to “compress” the body of the round so that you reduce its outside diameter.  When you reach the back of the football section, cut the tape and smooth it out over the body of the round.  Test fit the round into the barrel of the M203.  What you want is for the round to easily slide into the barrel but not so loosely that it just falls out.  It should be snug enough to stay in place but not any more snug than that. If it is too snug, unwind the tape and start over making sure to compress the round more than before.  If it is too small, unwrap the tape and start over making sure not to compress the round as much as before.  It is a matter of trial and error but after you do a few you’ll get the hang of it.

Keep the fins on the Nerf round the way they are.  They will be larger than the barrel so when loading the round give it a little twist to get the fins in the barrel.  They will go in easily and straighten out when the round is fired.

Airsoft M203 vs. the Metadyne Launcher

As many have pointed out the Metadyne Launcher is basically an improved version of the airsoft M203.  Where as the airsoft launchers require a shell, fill adaptor, and the modifications we talked about above the Metadyne launcher uses the marker’s air supply to power it eliminating the need for shells.  The Nerf rounds are muzzle loaded and the launcher be reloaded very quickly.  It too attaches to a Picatinny rail and weight is similar to the loaded M203.  Cost is about the same as the M203 with shell and fill adaptor as well making it a very attractive alternative. 

There are only two downsides to the Metadyne launcher.  First, you have to modify your marker to accept the launcher.  You have to run air lines from somewhere on your marker into the launcher.  This can require drilling and taping of your receiver and some are not comfortable with making such modifications.  This also means that to remove the launcher from the marker requires tools and for the user to plug the air supply feeding the launcher.  Anytime you modify the air route in your marker you run the risk of developing an air leak somewhere around the modification.   With the airsoft launchers two thumb screws will remove the launcher from the marker if you wish to use your maker without it and there are no modifications to the marker itself to mount the launcher.

The only other issue I personally have with the Metadyne is looks.  It doesn’t look as realistic as the airsoft launchers.  Because I am a MilSim player this is a big deal to me but for most this is not that important.  Again, that’s just me.


Another handfull of players sent to the deadbox. Courtesy the M203. Photo provided by PaintballPhotography.com

So you want a grenade launcher?  They certainly not are for everyone but for the right person they are a blast...pun intended.  There is something very intimidating about them (the first time you surrender someone with an M203 attached to your marker be polite and don’t bust up laughing at the look on their face as they stare down that big barrel) and it’s nice to take out seven or eight players sitting across the way in a building your just took out while keeping them all behind cover with your marker.  Just know that these launchers are almost addicting once you start playing with one as they are fun to use. Don’t say I didn’t warn you!

Good luck, and remember, it is all about having fun.

- Robotech

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