Boomer686 - A bit earlier in the thread....
CBSA collects taxes owing, plus a fee for processing the package. The processing fee will be $8 or $5, depending on whether the order was travelling priority or not - they charge more for for clearing a priority order.
Brownells will charge for USPS Priority air shipping, plus an export fee for preparing the SED paperwork.
Some US manufacturers are not registered with the US DOS for export. If they are not registered, Brownells cannot export any of their products. If you ask Brownells export department, they will email you the current list of registered manufacturers. Many of the goods in Brownells catalogue are exportable, many are not, because of this.
If you want to place a higher value order, or order controlled goods, subject to an export permit, Brownells will work with you. Many other US businesses will not.
I place "split" orders back to back. I use a fax, and give the orders separate PO numbers. I run the value of gun parts as close to the limit as I can, then add any other items I need.