I did some calculations using published figures for Hi-Force 44 (4% Ag, 96% Sn): Shear Strength = 14000 psi to 28000 psi. Assuming a 12 ga gun, 2.5", 2.75" and 3" barrel shank lengths, and .800 in. diam., AND shear strength of only 2000 psi, I calculate the following max. loads to shear the joint:

2.5 in., Area = 6.28 in^2, load = 12500 lbs
2.75 in., Area = 6.91 in^2, load = 13800 lbs
3.00 in., Area = 7.54 in^2, load = 15078 lbs

If I assume a shear strength of 14000 psi, I find the following:

2.5 in., Area = 6.28 in^2, load = 88000 lbs
2.75 in., Area = 6.91 in^2, load = 96800 lbs
3.00 in., Area = 7.54 in^2, load = 105600 lbs

My conclusion: a positive mechanical lock is probably unnecessary for a relatively mild cartridge.