8mm

[Junto]

I've been concerned, as of late, about the actual joules coming off of a .27 (lightest weight) 8mm BB. So I tracked down the FPS calculator from Arnies and punched it in.

AEG Limits with .20 BBs

330 for CQB= about 1 joule (1.01)
400 outdoor= About 1.5 joules (1.48 )
550 for bolt action rifles= About 3 joules (2.8 )

Any 8mm gun firing .27s

330 for CQB= 1.36 joules
400 outdoor= 2 joules
550 for bolt actions (VFC Barrett, etc.)= 3.77 joules

Seeing as our FPS limits are more about the joules delivered than the actual FPS, I'm concerned about people being permitted to exceed the safety limits with 8mm guns. To get 8mm guns back to AP safety standards the limits would have to operate thusly.

285 for CQB= about 1 joule (1.01)
345 outdoor= About 1.5 joules (1.48 )
475 for bolt action rifles= About 3 joules (2.81)

Your thoughts, gents? I've seen more and more 8mm guns out and about (mostly the marushin shotguns).

[KA-BAR]

sounds like good math and a great start.

[danneskjold]

I am a history major and want nothing to do with science...but isnt the physical size of the BB matter as well?

[Nocte]

Larger objects will have more surface area, and thus, more drag, meaning, they will have slowed down more by the time they reach their target. I'd suggest getting these calculations done (by someone who knows their shit* and can back it up) before proclaiming 8mm bbs unsafe.



*A friend of mine recently got his Master's Degree in Physics. I'll see if I can get him to give us some answers.

[dr.feelgood]

Although a larger bb may have slightly higher drag, the drag of a perfectly smooth sphere is fairly negligible*. What is felt when impacted by the bb is the transfer of momentum, and momentum (p) = mass (m) * velocity (v), p=mv. If V stays constant, and M is increased then the momentum would also increase. I haven't been to any games where there have been any 8mm guns (lately), so naturally I haven't noticed a problem. However if 8mm guns are being held to the 330 fps standard, whilst using a .28 g projectile, this would be the same as people using .28 6mm bbs so sneak under the chronograph for cqc. I am aware of someone who was using .28s when being tested for cqc, this was a long time ago, and was able to get a 390 gun to clock at 330.

* I am not a physic major, and I also didn't sleep at a holiday inn last night. But if we are talking CQC specifically (where I personally have the most concern of 8mm shotguns shooting hotter than I care for), then the engagement distances would be short enough the higher inertia of the heavier rounds would easily makeup for the increased drag.

[Junto]

I wasn't really moving to proclaim them unsafe, but rather spark a debate, with decent reasoning, to make some sort of ruling for 8mm guns, rather than never talking about it.

[FishSlapRepublic]

Also being bigger the impact is spread out which should cause less damage.

[Nocte]

I wasn't really moving to proclaim them unsafe, but rather spark a debate, with decent reasoning, to make some sort of ruling for 8mm guns, rather than never talking about it.

LIIIIES

[Beran]

the 8mm angle has been considered. its done the same way as 6mm, with weight factored in. since .20g isn't made in 8mm caliber (it feels weird using that word in relation to airsoft) the rules are essentially as you posted them. its by energy, not actual fps.

[chapped]

It's all about mass.

1) a housefly travelling at 30 mph hits you in the face.
2) a Mack truck travelling at 30 mph hits you in the face.

Which hurts more?

[Darius137]

[chapped]

Well played sir!
Well played!

[Bigfoot]

Most 8MM guns don't chrono very high so they are safe for outdoor play. Barrett was able to get his shotgun below CQC limits by just using duster gas instead of propane.

[Kendodude]

Most 8MM guns don't chrono very high so they are safe for outdoor play. Barrett was able to get his shotgun below CQC limits by just using duster gas instead of propane.

Somebody else used Duster around here other than me? O_O
OH MY GOD.

[Matt]

8mm BBs would have to follow the same rules for joule outputs, that's why we measure it by joules in addition to feet per second. However, I do agree that a separate set of numbers should be posted for 8mm so that we eliminate any confusion.