I'm not a lawyer, but looking carefully at the final bill it seems that if you lawfully possessed newly illegal weapons before the enactment you can in fact take them to an off of state range
Line 165-167
(a) prohibitions - except as provided in subsection (b) or (c) of this section, it is unlawful for a person to do any of the following:
(1) transport a weapon into the state
Line 204
(c) exceptions
Line 216
(3) a prison who lawfully possessed, or completed the purchase of an assault weapon prior to [effective date of this act], may possess and transport the assault weapon on or after [effective date of this act] only under the following circumstances:
Line 221
b. While on the premises of a shooting range
Line 225
d. While transporting the assault weapon between any of these places set forth in this paragraph (c) (3) of this section...... if the person places the assault weapon in secure storage
To me that reads if you are in lawful possession, and you drive from your home in delaware to, for instance, TSS in PA with it secured in your vehicle, then right back to your home in delaware, with no stops in between, you'd be fine to do so
It also seems like you could go from your residence to another's residence, even outside of the state, as long as you have permission from the other person to do so. So if you have a buddy with lots of land in PA that you might want to shoot on you'd be fine in that instance as well
Again, I'm not a lawyer and it's a lot to decipher, but to me that's what it looks like
Of course, that all accounts for states like PA to not have its own bans in place, like delaware's other border into Maryland