They also produced the Shikari in 44 rem mag so it must be stronger than the trap door rifle. I know the 44 is not a high preassure bottleneck round but is more so than the 18,000 to 20,000psi rounds loaded for the trap door.

FWIW, Buffalo Bore offers a 500gr jacketed bullet cartridge with a MV of 1625fps, according to their website, is suitable for use in a handi rifle. My motive for reviving this thread is I want to work up a load for a 1600fps, 500gr hornady RNSP load for my NEF SB2 handi. I've got a few recommendations so far, just wondering if anyone has any thoughts on this quest? thanks



http://www.buffalobore.com/ammunition/default.htm#4570



BTW, H&R does offer the .450 Marlin accessory barrel for the Ultra Rifle on their list.



http://www.hr1871.com/barrelAcc/index.htm