Servicing a Dynatex BFG

Dynatex BFG Grenades. How to service them.

I have a couple of the new style Dynatex blank firing grenades (BFG’s). One of them started to go off almost as soon as the pin was pulled rather than after the normal 5 second delay. So I decided to take it apart to see what was going on. Sorry, no pictures at the moment, but next time I take one apart I’ll get some pics.

First, how to get in to them. The metal top of the grenade is press fitted into the plastic body. To remove the top, warm the upper half of the grenade with a very hot hair dryer for a few minutes or place the grenade in a warm oven (100c). Once the plastic is warm it is a lot more flexible.

Remove the cap where you stick the blank and instead of a blank inset a long bolt so that the shaft of the bolt passes through the hole in the cap. Screw the blank housing back into the top of the grenade and use the protruding long bolt shaft to lever out the entire top of the grenade from the warmed up plastic shell. You will only be able to get the top off if the plastic shell is hot, if it’s cold it won’t come out and you risk damaging the grenade.

Once the top is off the internal mechanism is very simple. The issue with mine was dirt under the upper (smaller) O-ring. This O-Ring acts as a one way valve to help you prime the grenade, any dirt under it will let air back through in effect keeping the valve open and the grenade will fire prematurely.

I recommend removing and cleaning both O-rings and then apply a very small amount of silicone grease to them. You only want a very, very small amount of grease as any excess grease will attract dirt and dust and could lead to more problems in the future.

You will also find a small allen head grub screw in the nylon shuttle. You can use this screw to adjust the timing of your grenade. Screw it in (clockwise) to increase the delay and turn it anti-clockwise to decrease the delay.

Reassemble the grenade by again warming up the plastic body and gently tap the top back into the body. If the body is warm enough it doesn’t require much effort to get the top back in.

For replacement pins you can buy split pins from any good car spares store and use a key ring ring for the pull ring.

Green Gas or Propane?

Airsoft gas test, green, propane, mapp.

Reading various blogs, forums and articles I found it hard to find reliable information on some of the different gasses avaialble for airsoft gas guns. As I use a number of GBB rifles and pistols I decided to test out some of the gasses I have been using. These include 2 different brands of Propane, two different brands of MAPP (propylene/LPG, yes that’s right LPG) and an off the shelf “Green Gas” I used my WE M4 and my custom WE L22A2 for the tests firing 3 bb’s from each gun and chronoing them.  To try to keep the test even I used a separate mag for each gas and the mags were filled a couple of hours ahead of the test. It was fairly warm in the workshop when I did the tests, about 22c which explains the high results for guns set up for the UK. Previously I had set the NPAS valves on the guns for 340fps when the ambient temperature was around 10c. It really is amazing how much more gas pressure you get with all of these gasses when it’s warmer.

The gasses tested were:

Coleman Propane: Typically around £10 for 465 grammes (£0.021/g).

Rothenburger Propane: From many DIY stores, around £12 for 400 grammes (£0.03/g).

Rothenburger MAPP/PRO: From many DIY stores, around £16 for 400 grammes (£0.04/g)

Today’s Tools MAP-Plus: Online, from about £13 for 453 grammes (£0.028/g)

ProTech Green Gas: I got this off ebay, 3 x 1000ml cans for £30, so about £7.50 a can. Each can has approx 300 grammes of gas (£0.025/g)

Green Gas Testing

Before I get on to the chrono results a couple of observations:

Both of the MAPP gas gasses were less smelly than propane, but still hand a distinct odour that many may find unpleasant.

The coleman propane odour was stronger than the Rothenburger propane. Same smell, just more of it from the Coleman gas.

On to the results: 3 0.2g bb’s fired from each gun with 3 seconds between each shot.

Coleman Propane:

 M4 370 362 349fps

L22 407 346 374fps

Rothenburger propane:

M4 361 371 371

L22 411 406 404

Rothenburger MAPP-Pro

M4 410 396 379

L22 428 383 334

Today’s tool MAP-Plus

M4 367 358 356

L22 410 406 404

Protech green gas

M4 350 352 340

L22 395 391 389

Co2 (WE Co2 M4 Gas Magazine).

M4 405 392 396

L22 399 397 398

So what do I see in these results? Well I am surprised by how much lower the fps from the Protech green gas is. I tried a different magazine in case there was an issue with the magazine but got almost identical results.  I included the C02 Magazine just out of curiosity and one interesting observation is that the M4 and L22 are much closer in terms of fps when using the Co2 magazine.

There is little surprise that there is very little difference between the two propanes. The propane gave about 8% more power than the ProTech Green Gas, I could actually feel more recoil. The Rothenburger propane appears to have less cool down fps reduction. I don’t know why this would be.

The Today’s Tools Mapp-plus was no different to the propane. I tried to use this particular gas in the winter and didn’t get good results with a lot of cool down and never got the guns to work in the cold with this brand of MAPP.

The Rothenburger MAPP-Pro gave the highest fps (so I must assume has the highest gas pressure) but also exhibited the greatest amount of cool down. The magazine felt noticeably colder than the other mags after the test. When I used this gas in the winter it was good for infrequent semi auto fire, but got very cold, very quickly if you tried to fire too rapidly.

The ProTech Green Gas produced the lowest fps, but stayed pretty consistent. I’ve used this gas for a few skirmishes and it’s been OK when the weather has been above 10/12c. I wish I had some other green gasses to try.

In conclusion, for me at least I will probably use the Rothenburger Propane. The Coleman propane is a bit cheaper but it is very smelly. I can buy the Rothenburger Propane in my local Screwfix or Wicks for £12 a can. If I buy a pack of 6 from Screwfix then it’s only £10 a can making it just £0.025/g, almost as cheap as the smelly coleman propane and cheaper than most airsoft green gassed. If you can live with the smell then the best bang for your buck is the Coleman Propane. I would probably avoid the Today’s Tools Mapp-plus.

Lessons Learnt During Operation Barracuda (Longmoor)

I had a great day playing at Longmoor. One of the key things to take away from an event like this is the importance of good communications when many teams or squads are operating over a large area. Being able to quickly call in reinforcements when a position is in danger of being overrun can be a game changer.  good radios make a big difference, but you don’t want everyone chatting on the primary net frequency. The command and control channel needs to be kept clear and should only be used for requesting tasking,  issuing instructions or emergency comms. Within each squad it is handy to have a separate channel for use when spotting the enemy, for general well being checks and other chatter. In a squad of 8 or so players it would make sense for each player to have a radio on the squads “chat” channel while the squad leader or designated comms person (“bleep”) has an additional radio on the command and control channel.

Using standardised hand signals allows players from different teams or players that are not members of a team to group together into larger strength formations for large scale assault or defence operations.

There’s smoke and then there’s smoke. Smoke is a great way to create a temporary screen to allow hidden troop movements. At Longmoor it was very useful to help with the extraction of wounded players or the movement of troops and materiel. But some smoke grenades are better than others. I had purchased some TLS-FX white smokes for the event at longmoor, but frankly the amount of smoke produced was so small that they were useless as a defensive screen. I had much better luck with some Enola Gaye coloured smokes left over from other events.

Also fiddling around with the striker caps from smokes and grenades in the heat of a battle is fiddly at best and it easy to loose the striker cap. I will be getting a velcro backed striker pad that I can attach to the front of my plate carrier so I no longer need to rely on the ones attached to the pyro’s.

Hand Signals

Hand signals are an important means of communication on the battlefield. They make no noise and can be seen over large distances. The same signals are used by most forces around the world. Here are some examples.


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