IAS Problem: Calculation vs Testing

[PFSS]

I'm building a bowazon and am getting a discrepancy between calculated and tested rates of fire.

I am using a Faith Grand Matron Bow with a level 15 Fanaticism aura and my IAS gear is:

Test 1: Laying of Hands + Highlords = 40% IAS
Test 2: Laying of Hands + Highlords + Guillaume's Face with 15% IAS Jewel = 55% IAS

Based of the Amazon Tables by Kijya these will give:

Test 1 = 9 Frame Attack
Test 2 = 8 Frame Attack.

I wanted to make sure I was reaching the next breakpoint and that I understood the tables correctly. To carry out the tests I went to the Blood Moor and held down the attack button for a timed two minutes for each gear setup. To count the arrows fired I started with a full quiver (350) and subtracted the arrows remaining after two minutes of constant firing on 'normal attack'.

Test 1 = 72 Arrows Remaining = 278 Arrows Fired in 120 seconds
Test 2 = 40 Arrows Remaining = 310 Arrows Fired in 120 seconds

As I understand there are 25 Frames/Second which gives:

Test 1 = 120*25/278 = 10.79 Frames/Attack
Test 2 = 120*25/310 = 9.68 Frames/Attack

Which is very strange - the attacks are both a fair bit slower than would be expected and are not even an exact number of frames. Even allowing for a few arrows extra or less due to error in timing the Frames/Attack will not be an integer.

Is my computer just running the game at the wrong frame rate? Or am I missing something here?

Thanks in advance.

[Kijya]

Are you sure about the test setup you are listing?

I mimicked your 9 fpa test using:

Shael WF = 40 IAS (other ias sources removed)
Faith merc (lvl 15 aura)


Used normal attack straight for 2 minutes and got 16 arrows left from starting with a full stack:

120 * 25 / (350 - 16) = 8.982035928


I threw on 15 more IAS with my ias jeweled griffons and then my arrow stack ran out at about 1:52 = 112 seconds

112 * 25 / 350 = 8 ... suspiciously precise but that's what I got ....



My guess is that you where keeping an extra set of arrows in your inventory somewhere that you had overlooked, once your first stack ran out that one was equiped and messed up your test.