Have a look at MTOW-s:
Gulfstream 550 - 41 277 kg.
Gulfstream 500 - 38 601 kg.
Gulfstream 450 - 33 521 kg.
Gulfstream 350 - 32 160 kg.
Compare Falcon 7X - 31 299 kg.
No wonder Falcon has less range than G550: it has much less weight. I suspect that Falcon 7X does more with the same fuel than G350 can. G350 range is 3800 nm, cabin length 13,7 m. Slightly longer than 7X, but narrower.
Bombardier Global Express XRS - 44 452 kg.
Bombardier Global 5000 - 41 957 kg.
Bombardier Challenger 605 - 21 683 kg.
Bombardier Challenger 850 - 24 041 kg.
Challengers have a rather limited range. Challenger 850 has large cabin (no wonder - airliner!) and therefore short range for weight, while Challenger 605 also has maximum range of just 4045 nm.