Here are the tech specs as sourced from II CORPS documents.
7.2 Inch T40 Rocket Launcher:
                Weight of Launcher: 5,500lbs empty,6,700lbs   
                fully loaded
                Tubes: (20) 90-inch tubes, 2 rows of 10
                
Tube Material: Sheet steel
                Life of Tubes: Indefinite
                Firing Method: Electrical, single-shot or ripple 
                fire
                Maximum Firing Rate: 20 rounds in 10 seconds    
                (ripple fire)
                Muzzle Velocity: 160 feet per second.
                Maximum Range: 230 Yards
                Effective Range: Typically 60-75 Yards
                Rocket Type: 7.2 Inch High Explosive Rocket T37 
                Rocket Dimensions: 61 lbs, 35 inches long
                with circular fins
                Explosive Charge: 32 lbs of C2 plastic explosive
                Laying on Target: By turret gun sight
                Traverse and Elevation: Traverse by turret, 
                elevation by main gun.
                
Main Gun Operation: Can be fired with    
                launcher installed 
                
Jettison Capability: Hydraulically .
                jettisoned in seconds
                Armor Plating: Will divert up to .30 caliber 
                bullet
                
4.5 Inch T34 Rocket Launcher (Standard 60-Tube Unit):
                Weight of Launcher: 1840lbs empty, 4240lbs fully 
                loaded
                Tubes: (60) 90-inch tubes, 2 rows of 18 on top, 
                launcher installed 2 rows of 12 on bottom
                
Tube Material: Plastic
                Life of Tubes: Begin breaking up after 4 salvos, 
                average life 15 to 20 salvos    
                Firing Method: Electrical, single-shot or ripple 
                fire
                Maximum Firing Rate: 60 rounds in 30 seconds 
                (ripple fire) 
                Muzzle Velocity: 850 feet per second
                Maximum Range: 4,600 Yards
                Effective Range: 3,900 Yards
                Rocket Type: 4.5 Inch Aircraft Rocket with 
                (ripple fire)
                Rocket Dimensions: 40 lbs, 33 inches long, 
                fin-stabilized
                Weight of projectile in flight: 15.25 Lbs
                Rocket Flame: 30 to 40 feet
                Explosive Charge: 4.3 lbs of TNT explosive
                Conventional Blast Equivalent: 105mm shell
                Laying on Target: By turret gun sight
                Traverse and Elevation: Traverse by turret, 
                elevation by main gun
                
Main Gun Operation: Cannot be fired until 
                launcher is jettisoned
                
Jettison Capability: Hydraulically 
                jettisoned in seconds
                Armor plating: None
It took a crew of five up to two hours to reload and reconnect electrical wires. Also as shown above, they could launch single rockets or some combination (or all) of rockets for a sequenced or full "ripple launch". Most of these tubes actually came off combat aircraft.
The other key points I highlighted. Previous references from earlier posts might help, to include the War Dept. film from the You Tube ref.
http://www.tanks-encyclopedia.com/ww2/US/M4_Sherman.php
Regards,
Pat
