You're right, Smolt! I ran some tests with a 5 LBS and a 10 LBS weight and realised a tiny bit of friction can cause some discrepancy, and also the position of the lever as the weight pushed it down.
Test 1
5 LBS on pin B with pulley system: 109 LBS
I noticed that if I tapped the lever, the weight would fall even more (friction)
New reading: 148 LBS
Test 2
10 LBS on pin B with pulley system: 265 LBS
Same thing; I tapped the lever, the weight would fall even more (friction)
New reading: 300 LBS
I did a few more readings with the ''lever tap'' and it would be a consistent 145-152 LBS readings with a 5 LBS, and exactly DOUBLE on the 10 LBS weight.
Mechanical Advantage: 30-ish
As the lever was pushed down by the weight, the angle got more pronounced (greater than 30 degrees). Now I see that the MA will vary a bit depending on the lever position.
Thanks for clarifying, smolt! I am now a little scared of my press
Now I need to figure out a way to avoid destroying my mould lid...