Fluid end with clamped retention

A fluid end, comprising:

• a housing having a longitudinal axis and opposed front and rear surfaces joined by an outer intermediate surface;
• a bore formed within the housing and interconnecting the front and rear surfaces, the bore extending along the longitudinal axis of the housing;
• a retainer abutting the rear surface of the housing;
• a clamp surrounding and engaging at least a portion of the retainer and at least a portion of the housing and securing the retainer and the housing together, the clamp comprising:
• an inner clamp surrounded by an outer clamp;
• a reciprocating plunger disposed within the bore and the retainer;
• and
• a packing seal installed within the housing and engaging an outer surface of the plunger.