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Description

Time to put some meat into the pistol!

I created a loading mechanism based upon a gas-operated lever-action rifle. That gave me enough room for a proper barrel within a small package.

A notable feature of the official cartridge design is that it is both cylindrical and has three rings around it. That makes it potentially suitable for a different approach for the chambers that helps to cut down the entire length of the weapon even further: when the breech closes the cartridge is shoved backwards into the deep cavity of the breech, encasing the whole cartridge except for the front rim which sits inside the actual barrel and is kept in place by two fixing hooks. With all three rings having the same diameter and the cartridge using the high/low pressure system to propell the rocket out of the barrel, the main body of the cartridge only needs to be relatively thick-walled to withstand the pressure on its own, with the middle ring supporting it by diverting parts of the load to the breech wall. For RL comparison: a 40 mm grenade cartridge has a chamber pressure inside the high-pressure chamber of 241.4 MPa but only 20.6 MPa inside the low-pressure chamber behind the actual projectile. Using a halfway strong brass for the cartridge (Rp02 of 480 N/mm²), that would mean a wall thickness of 0.4 mm would be just enough to withstand the chamber pressure - take 0.6 mm and add the effect of the supporting ring in the middle,and your margin of safety is more than enough to prevent the case from rupturing when the round is fired.

Description

Time to put some meat into the pistol!

I created a loading mechanism based upon a gas-operated lever-action rifle. That gave me enough room for a proper barrel within a small package.

A notable feature of the official cartridge design is that it is both cylindrical and has three rings around it. That makes it potentially suitable for a different approach for the chambers that helps to cut down the entire length of the weapon even further: when the breech closes the cartridge is shoved backwards into the deep cavity of the breech, encasing the whole cartridge except for the front rim which sits inside the actual barrel and is kept in place by two fixing hooks. With all three rings having the same diameter and the cartridge using the high/low pressure system to propell the rocket out of the barrel, the main body of the cartridge only needs to be relatively thick-walled to withstand the pressure on its own, with the middle ring supporting it by diverting parts of the load to the breech wall. For RL comparison: a 40 mm grenade cartridge has a chamber pressure inside the high-pressure chamber of 241.4 MPa but only 20.6 MPa inside the low-pressure chamber behind the actual projectile. Using a halfway strong brass for the cartridge (Rp02 of 480 N/mm²), that would mean a wall thickness of 0.4 mm would be just enough to withstand the chamber pressure - take 0.6 mm and add the effect of the supporting ring in the middle,and your margin of safety is more than enough to prevent the case from rupturing when the round is fired.