Down Fill-Weight Variances?

[Trail Runner]

Apologies if this has been asked & answered before but I couldn't find the info I was seeking. I'm in the market for my first under quilt and have narrowed down my choices to 3 different manufacturers. In comparing the ¾-length 40F quilts I'm interested in I've noticed that there is a significant difference (as much as 50%) in the fill-weight being used by the three. Each are using 850 Goose Down. There are slight differences in the size of the quilts but not enough to account for the variance. Why the variance and what I am I missing?

Thanks

[gmcttr]

Links to the specific UQs would let us take a look at them to find the differences.

[Trail Runner]

It turns out one of them was using 800 Goose Down but the other 2 are where the big variance is. Here are the links:

HG Phoenix 40

UGQ Zeppelin 40

HG is using 4oz of 850 Down (see specs tab) compared to UGQ using 6oz of 850 Down. The Zeppelin is 2" wider & 3" longer but surely that can't account for the variance.

[gmcttr]

By my calculations, and I could be wrong, the larger dimensions account for about 9% of the difference.

What we don't know, are the height of the HG baffles and the % "overfill" each maker uses. Either of these could account for the difference. There is no industry standard for what amount of loft constitutes a 40* UQ so each maker uses their own preference/judgement.

Also there is a major construction difference between the two UQs that could account for a difference in fill weight as well.

The HG Phoenix has taller baffles in the torso area than in the leg area, concentrating the fill where it is needed the most while saving weight and compressed size.

UGQ Zeppelin appears to have uniform baffle height with the same amount of loft in the leg and torso areas.

[Trail Runner]

Thanks gmcttr, that makes sense. I was mistakenly operating under the assumption that there was a specific formula equating the amount of fill to the R value or temp rating.

[gmcttr]

I think the closer correlation would be between R value and loft and construction details can allow or restrict loft.

[Boston]

Hammock Gear uses Argon fabric, which is ~25% lighter than the illume Underground Quilts uses. That with the other factor's listed account's for most of the weight difference.