Enforced BB weight limit

[MalcyFett]

I’ve had a good few months away from Airsoft, on my return I’ve been advised that the usual sites my chums visit have BB weight limits now for outdoor sites.

 

Gunman, GZ and UCAP all saying max weight of .32g on HPA/AEG/GBB.

 

I generally use .32 anyway, but curious if this is now the norm for most sites.

[Hami]

First I’m hearing of it 

[Adolf Hamster]

It's a rule that has some logic behind it, ablbeit the lazy logic of a site that finds it easier to enforce an unenforceable rule than take the steps to ensure proper chrono practice.

 

Tl:dr is hpa/gbbr has a tendancy to joule creep, ie it can fire kosher joule-based owchie on 0.2g but significantly more than the allowable joule-based owchie on heavier rounds, so a (theoretically unsuspecting) player can pass chrono with flying colours and with no more effort than loading their preferred heavyweight ammo be dishing out unnessecary zingers to their fellow humans.

[Rogerborg]

It's not generally accepted yet, but I'm fine with it. Above about 0.4g you have to mix in so much metal and minerals that it becomes hard to argue that we're slinging "plastic".

[Galvatron]

UCAP doesn't surprise me and I think it's reasonable.

 

With a weight cap, it saves having to enforce an MED in the CQB areas of their mixed outdoor and indoor sites. At least that's what I assume the rationale is.

[GiantKiwi]

It's actually fairly common up here.

 

Which would be fine, except its not founded in logic or understanding of physics.

[Rogerborg]

6 hours ago, GiantKiwi said:

Which would be fine, except its not founded in logic or understanding of physics.

 

Why don't we shoot each other with steel BBs?

[Anonymoose]

20 minutes ago, Rogerborg said:

 

Why don't we shoot each other with steel BBs?

 

 

100% biodegradeable!

[Cannonfodder]

I've only ever seen it at cqb sites where shooting someone with a heavier bb is going to cause more pain.

 

 

19 hours ago, Galvatron said:

UCAP doesn't surprise me and I think it's reasonable.

 

With a weight cap, it saves having to enforce an MED in the CQB areas of their mixed outdoor and indoor sites. At least that's what I assume the rationale is.

That makes sense. Restricting certain weight bbs to some areas of the site would be a ball ache for players to stick to and almost impossible to enforce by staff.

 

Of course if the site doesn't have cqb areas then its a bit pointless imo. If it's done to try and prevent joule creep then surely its better to just chrono on whatever weight is used in game

Edited 12 hours ago by Cannonfodder

[Hatchet]

This thread needs more science.

 

Assuming rounds weighing 0.2g and 0.4g leave the gun with the same kinetic energy (joules), what's the difference in impact at point blank/10m/20m/30m? 

The heavier round can't *gain* any more energy (although it can lose it less quickly).

 

Brain hurts.  

[mightyjebus]

There are smarter people on here than me but as far as I remember from school:

 

Velocity and Mass are inversely proportional, so it takes a 0.4g bb twice as long as a 0.2g bb to get to it's maximum velocity. based on a 1J AEG then somewhere along the flight time the 02.2g BB will reach maximum velocity and at double that distance the 0.4g BB will do the same.

 

o.2g and 0.4g BB's will have different momentum on a static object (i.e. a person) and the Mass + velocity will be transferred as momentum to the solid object. If you increase the mass or velocity then the momentum transferred will be greater. 

 

Velocity and Mass are why you get Joules creep. If the BB hasn't fully accelerated by the time it goes through the chrono then you don't actually know the power the BB has. So more mass (0.4g BB) plus Joules creep = more momentum which translates as harder impact.

In CQB at close ranges the 0.4g BB will transfer the Mass, gained momentum and any velocity still to be used up as the BB was accelerating so you don't loose anything even if the BB hasn't got to full speed.

The momentum (impact) will vary on the static target depending on the angle that it was struck and the material is is made from (plate carrier good, exposed flesh bad).

[Hatchet]

But isn't joule creep the heavier bb continuing to receive acceleration force in the barrel after the point at which lighter BB would have already exited? (and this only when there is more acceleration i.e. cylinder capacity, left to give). At the point its *left* the barrel, it surely can't have any more acceleration force acting on it. It demonstrably can't be the case that if you chrono'd it 20m out it would have more energy than previously, right?

 

(Disclaimer, I don't know any of this stuff and have been drinking, so...)

[mightyjebus]

it depends on where the BB reaches maximum acceleration. If it's inside the barrel then the energy measured at the muzzle will be the maximum joules it can achieve. A heavier BB could still be accelerating as it leaves the muzzle and doesn't reach maximum velocity until xx distance (double that of a 0.2g BB). Another way to think of it is the BB has had the energy applied but it takes time (in our case distance) before the full effect takes place. Think of a rocket taking off, it doesn't go from zero to maximum right away, it slowly creeps forward and accelerates every meter it climbs until it's at full velocity. The rocket power is the same at 0 feet as it is at 1000 feet but the rocket is travelling at 2 different speeds at those 2 distances. (ignore the fact that the rocket is fighting gravity and we will be fine with this analogy).

 

I suspect that part of the reason for heavier BB's to travel further is that they are accelerating for longer so don't start to slow down as quickly as a lighter weight BB which reaches maximum acceleration quicker over a shorter distance, reducing the overall flight time compared to a heavier BB. Friction will affect the heavier BB more and gravity will also have some effect but it doesn't seem to be linear when comparing 0.2 and 0.4g BB's

 

One way to test this would be to line up a couple of chrono's and shoot some heavier weight BB's through them to see at what distance the BB peaks in joules.