Model BOM & IDW vs Model Total Weight

[darrell.badger]

I have an interesting twist on the BOM that I just can't get to the heart of:
The IAM assembly weight (from iProperties) is 23861.242 lbsmass.
However, by hand calculations the weight should be closer to 26,000 lbs based on prior assemblies.

When I go to the Bill Of Materials dialog for the assembly and export the list to excel (with some minor processing) I get a BOM weight of 25954.334 lbmass.
I have checked item by item and wt by wt the IDW BOM and the IAM BOM to each other and they are exactly the same.

I have checked to be sure that the IAM BOM is referencing the same Level of Detail.

I am at a complete loss as to how Inventor can report two different weights (by over 2000 lbs from the exact same model.

[darrell.badger]

To update everyone, there were two issues:
1) I did not check the BOM's consistently and the designer hid two line items. After correcting for this the two BOM's matched.

2) I found that my designer made several sub-assemblies within the upper assembly and set each sub-assembly to Phantom. Generally not a big deal. The sub-assemblies were made up of several layers of different materials in a rectangular shape with cutouts for piping, doors and structure. The actual parts were full sized what he did was subtract material in the sub-assembly from each part. By setting the assembly to phantom both BOM's ignored the final weight of the sub-assembly and listed the full weights of the parts without the cutouts. However, the upper assembly took the full weight of the sub-assembly including cutouts.

Unfortunately, this assembly is installed in another higher level assembly and that drawing listed a lower weight not matching the assembly weight.