[The Acer]

Here is the Mathmatic Proof that shows that using heavier bb hurts more

Lets say you have a 1 joule spring, same size bb, neglect friction and wind resistance, to keep this simple as possible


the formula of Kinetic Energy is as following
E = 1/2 * m * s ^2
E is in Joules
M is in KG
S is in m/s

two situations, .2g bb and .3g bb

With .2g bb
1 J = 1/2 * 0.0002 KG * s^2
s = 100m/s or 328fps

With .3g bb
1J = 1/2 * 0.0003 KG * s^2
s = 81.7m/s or 268fps


According to the Taylor Knockdown Formula
TKO value = m * s * caliper / k
m is in G
s is in m/s
caliper is in mm
k is constant, 3507

With .2g bb
TKO = .2 * 100 * 6 / 3507
TKO = 0.0342

With .3g bb
TKO = .3 * 81.7 * 6 / 3507
TKO = 0.0419

As you can see the heavier bb has a bigger TKO value, hense more "penitration power" or would just hurt more.

or instead of Taylor Knockdown Value, you can use Momentum formula

P = M * V
P is the momentum
M is mass in KG
V is in m/s

with .2g bb
P = .0002kg * 100m/s
P = .02 kg m/s

with .3g bb
P = .0003kg * 81.6m/s
P = .02448 kg m/s

.3g has more momentum than the .2g, even though same amount of energy was applied


Hope this helps