I must honestly say that I do not know why the barrel is longer. My only guess would be that that round may need to burn more powder for optimum performance.

I'm wanting to get NEF's .223 with a bull barrell and survivor stock, then send it in to get a Muzzleloader barrell, 30-06 barrell, 12 guage rifled slug and 12 guage barrell with interchangable chokes. This would be, IMHO, an awesome collection.