Section VI-C:  Recommended Universal MED's

 

I've noticed that many sites use MED's that are gross estimates of impact energies.  It is an easily made, and honest mistake.  When we first began getting together, we had no MED for rifles firing at 1.15 J (up to 350 fps), yet had an MED of 100 feet for rifles firing up to 500 fps (2.3 J) and a maximum BB weight of 0.25g.  In hindsight, we realized that this places an unfair limit on snipers as players using AEG's could hit their targets with as high of an impact energy of 1.15 J, whereas a sniper limited to 100 feet with 0.25g BB's would be hitting their target with an impact energy of, at most, about 0.4 Joules.  After some calculations, we realized that we needed to determine our MED's based on a standard impact energy.  As stated earlier, I prefer to use a MED chart based on a maximum impact energy of 1.00 Joules for rifles/pistols, regardless of whether they're 6mm or 8mm rifles. 

 

The chart also corresponds to the weight of BB that the shooter is using, which is just as important as the muzzle energy.

 

 

 

Minimum Engagement Distances in Feet

Mass of Projectile Used in Match / Event

Muzzle Energy / Class

Muzzle Velocity (relative to 0.20g / 0.30g BB's)*

0.12g - 0.30g

0.31g - 0.43g

 

 

6 mm

 

 

 

< 1.2 Joules

<360 / 295 fps

15

20

1.2 - 1.5 J

< 400 / 325 fps

30

40

1.5 - 1.9 J

<450 / 365 fps

45

60

1.9 - 2.3 J

<500 / 410 fps

60

80

2.3 - 3.4 J

<600 / 490 fps

80

120

3.4 - 4.6 J

<700 / 575 fps

100

145

 

 

8 mm

 

Muzzle Energy / Class

Muzzle Velocity (listed as 0.34g / 0.45g max)**

0.34g

0.45g

< 1.5 Joules

<310 / 270 fps

20

25

1.5 - 2.3 J

<385 / 335 fps

35

50

2.3 - 3.4 J

<460 / 400 fps

55

70
3.4 - 4.6 J <540 / 470 fps 65 85

4.6 - 5.3 J

<580 / 505 fps

75

100

 

*    Because high-powered rifles -- particularly gas rifles -- are able to transfer more energy to heavier BB's, we require that all rifles/pistol that chrono at more than 400 fps with 0.20g BB's be re-chrono'd using 0.30g BB's.  The reason for this is covered in detail in Section VI-A:  Determining Muzzle Energy.  For instance, if a rifle chrono's at 570 fps with 0.20g BB's, we re-chrono the rifle to determine its muzzle energy using 0.30g BB's.  If the same rifle chrono's at 510 fps w/ 0.30g BB's (for example), we would use the 3.4-4.6 J section to determine the shooter's MED (and NOT the 2.3-3.4 J section).  If this player uses 0.30g BB's for that rifle, they would be given an MED of 100 feet.

 

**  Velocity listings for 8mm BB's are listed as the maximum for 0.34g and 0.45g BB's, respectively.  Example:  A rifle shooting at 2.3 J will chrono at 385 fps using 0.34g BB's, or 335 fps using 0.45g BB's.  If a rifle chrono's at 530 fps with 0.34g, you would use the 3.4-4.6 J section (which allows a maximum fps for 0.34g of 540 fps) and would have an MED of 65 feet.  If a rifle chrono's at 325 fps w/ 0.45g, they would use the 1.5-2.3 J section (and have an MED of 50 feet).

 

 

Click here for a printer-friendly version of the chart.

 

 

 

 

The above chart may seem complicated but it helps to ensure that there is a balance between power and safety without bias.  Particularly when a shooter is using heavy BB's, the MED's need to be increased as the heavier BB's retain their energy at a greater range.  For instance, if a site wanted to set a universal maximum impact of 1.00 Joule for sniper rifles, a sniper firing a 0.34g 8mm BB at 3.4 J would have an MED of 65 feet, whereas a sniper firing a 0.43g 6mm BB at 3.4 J or below (the equivalent of <600 fps with 0.20g) would have an MED of 115 feet. 

 

Take the example where a site has a maximum muzzle energy of 3.5 Joules for sniper rifles, and has a sniper MED of 100 feet regardless of BB type, believing that this would ensure that the impact energy would be below 1 Joule.  In this case, a person being hit by a sniper rifle firing a 0.43g 6mm BB at 419 fps (or 3.5 Joules) at the MED of 100 feet would experience an impact energy of 1.34 J, clearly above the 1 J limit the site intends to enforce.  By contrast, a person being hit by a sniper firing a 0.34g 8mm BB at 470 fps (again, 3.5 Joules) at the MED of 100 feet would experience an impact energy of a paltry 0.39 J.  In reality, to enforce a 1 J maximum impact energy would mean that the 6mm sniper rifle would be subject to an MED of 135 feet, while the 8mm sniper rifle would be subject to an MED of 55 feet. 

 

This is further illustrated by Figures VI-C-01 and VI-C-02:

 

Additionally, it should also be noted that the MED's listed above are for events at or below 2,000 ft MSL.  For higher altitudes (above 4,000 feet msl), 5-20 feet should be added to the MED's to ensure safety, i.e., you would add 5 feet for muzzle velocities around 200 fps w/ 0.20g, and 20 feet for muzzle velocities around 600 fps w/ 0.20g. 

 

As an example, at an event in Denver, Co., a sniper rifle shooting at 410 fps with a 0.43g BB (the equivalent muzzle energy of a 0.20g BB fired at 600 fps) would need to have their MED modified.  In this case, we would increase the MED by adding 20 feet, taking it from 110 feet to 130 feet.  This is illustrated in Figure VI-C-03:

 

 

If you would like for me to make calculations for your site's altitude or would like custom or truncated charts, please feel free to contact me at airsoft@cybersloth.org and I'll gladly generate either charts or tables for your site. 

 

 

 

Here is the same chart as above but modified in meters and meters/second (the numbers do not completely match those listed above as I've used slightly different muzzle velocities):

 

 

 

Minimum Engagement Distances in Meters

Mass of Projectile Used in Match / Event

Muzzle Energy / Class

Muzzle Velocity (relative to 0.20g / 0.30g BB's)*

0.12g - 0.30g

0.31g - 0.43g

 

 

6 mm

 

 

 

< 1.2 Joules

<110 /   90  m/s

5

6

1.2 - 1.5 J

<122 / 100  m/s

9

12

1.5 - 1.9 J

<137 / 112  m/s

14

19

1.9 - 2.3 J

<152 / 124  m/s

19

25

2.3 - 3.4 J

<183 / 149  m/s

25

35

3.4 - 4.6 J

<213 / 174  m/s

31

45

 

 

8 mm

 

Muzzle Energy / Class

Muzzle Velocity (listed as 0.34g / 0.45g max)**

0.34g

0.45g

< 1.5 Joules

<  95 /   82  m/s

6

8

1.5 - 2.3 J

<117 / 102  m/s

11

15

2.3 - 3.4 J

<140 / 122  m/s

17

22
3.4 - 4.6 J <165 / 143  m/s 20 26

4.6 - 5.3 J

<177 / 154  m/s

23

31

 

*    Because high-powered rifles -- particularly gas rifles -- are able to transfer more energy to heavier BB's, we require that all rifles/pistol that chrono at more than 120 m/s with 0.20g BB's be re-chrono'd using 0.30g BB's.  The reason for this is covered in detail in Section VI-A:  Determining Muzzle Energy.  For instance, if a rifle chrono's at 175 m/s with 0.20g BB's, we re-chrono the rifle to determine its muzzle energy using 0.30g BB's.  If the same rifle chrono's at 156 m/s with 0.30g BB's (for example), we would use the 3.4-4.6 J section to determine the shooter's MED (and NOT the 2.3-3.4 J section).  If this player uses 0.30g BB's for that rifle, they would be given an MED of 31 meters.

 

**  Velocity listings for 8mm BB's are listed as the maximum for 0.34g and 0.45g BB's, respectively.  Example:  A rifle shooting at 2.3 J will chrono at 117 m/s using 0.34g BB's, or 102 m/s using 0.45g BB's.  If a rifle chrono's at 162 m/s with 0.34g, you would use the 3.4-4.6 J section (which allows a maximum for 0.34g of 165 m/s) and would have an MED of 23 meters.  If a rifle chrono's at 99 m/s with 0.45g, they would use the 1.5-2.3 J section (and have an MED of 15 meters).

 

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