My understanding is Registered mail is just an add-on service which can be added to 3 day Priority mail and not nearly as expensive as Priority Express. Someone correct me if I am wrong, but I've recently been doing some shipping calculations since I'm selling some of my rifles.
I checked a price from here to Dallas, express was $75, priority registered was $66. Definitely a little cheaper, probably depends where you're shipping and what.
Yeah, mailing to or from AK bites. What I'm trying to figure out is the correct packing tape to use. That linked thread in the OP mentions some gummy tape. Looking through the postal regs, I found this:
3.10 Tape and Tape Size
A strong packaging or paper tape (not cellophane or masking tape) may be used for the closure or reinforcement of packages. Paper tape must be at least 60-pound basis weight kraft. The adhesives on gummed tapes must be adequately activated before application and firmly applied with the tape extending at least 3 inches over the adjoining side of the box. Except for pressure-sensitive filament tape, tapes used for closure and reinforcement should be at least 2 inches wide. Nonreinforced plastic tapes must be at least as strong in the cross direction as in the machine (long) direction.
But it might just be easier to go buy whatever tape they like at the post office.
