Ok, already i have asked couple times in the general support section about shipping calculation but of no use.
Now i will say it as a bug.
When using usps shipping module
and if i add a product of weight 33lb L-22 W-22 H-16 and then if i estimate i get correct value both from nop commerce and usps rate calucator. eg. 24.02 usd
When i set the quantity of the product to 2 and update the cart and again estimate the shipping cost, now it is still the same price as it used to be for 1 product.
The nopcommerece team should rectify this issue, not until next release.
It would be great if they post a small snippet to include class file that will solve the problem.
Now i am not using USPS rather using order by total for now, which is totally meaningless but i donot have a choice I have to launch the site and i am willing to take the losses.
Thanks for anyone who helps this issue.