On an SB2 Handi frame, the 445 Supermag would be a better option than the 44mag, 300gr at ~2000fps is doable in the Supermag and doesn't require an expensive rebore, the chamber can be hand reamed with a rented reamer, the hardest part would be waiting for Starline to make brass!
The 265gr FTX would be a prime candidate IMO.
Tim
http://stevespages.com/page8d.htmhttp://www.hornady.com/store/44-Cal-.430-265-gr-FTX-for-444-Marlin/Trajectory for Custom .430 Hornady 265gr FTX at 2100 Feet per Second
At an Elevation Angle of: 0 degrees
Ballistic Coefficients of: 0.225 0.225 0.225 0.225 0.225
Velocity Boundaries (Feet per Second) of: 2100 2100 2100 2100
Wind Direction is: 0.0 o'clock and a Wind Velocity of: 0.0 Miles per hour
Wind Components are (Miles per Hour): DownRange: 0.0 Cross Range: 0.0 Vertical: 0.0
Altitude: 0 Feet Humidity: 70 Percent Pressure: 29.53 in/Hg
Temperature: 59 F
Data Printed in English Units
Range Velocity Energy Momentum Drop Bullet Path Wind Drift Time of Flight
(Yards) (Ft/Sec) (Ft/Lbs) (Lb-Sec) (inches) (inches) (inches) (Seconds)
0 2100.0 2594.5 2.47 -0.18 1.13 23430.58 0.000000000
50 1929.0 2189.2 2.27 -1.04 2.86 0.0 0.074531190
100 1767.1 1837.2 2.08 -4.43 4.88 0.0 0.155783768
150 1615.6 1535.5 1.90 -10.6 4.11 0.0 0.244579356
200 1475.8 1281.4 1.74 -20.11 0.0 0.0 0.341757629
250 1350.0 1072.2 1.59 -33.62 -8.11 0.0 0.448088003
300 1240.3 905.1 1.46 -51.91 -20.99 0.0 0.564111556