A jarring device, comprising: a housing; a mandrel received within the housing and movable relative thereto; a pressure chamber defined between the housing and the mandrel and filled with a hydraulic fluid; and a hydraulic lock piston arranged about the mandrel and radially interposing the housing and the mandrel, the hydraulic lock piston including: a pressure piston (214a,b) having a first end exposed to the pressure chamber; a second end; first and second fluid flowpaths (506a,b) defined in the pressure piston (214a,b) and extending axially between the first and second ends (504a,b); a cap arranged at the second end and defining a first exit aperture aligned with the first fluid flowpath and a second exit aperture aligned with the second fluid flowpath, wherein the cap provides one or more cap lobes (522a,b) and the second exit aperture extends axially through one of the one or more cap lobes (522a,b); a valve plate arranged adjacent the cap and providing one or more valve lobes (404a,b) that intermesh with the one or more cap lobes (522a,b); and a bearing ring that mates with the valve plate when assembled on the mandrel, wherein, when the mandrel moves in a first direction relative to the housing, the hydraulic fluid is metered through the first fluid flowpath and the second fluid flowpath is occluded, and wherein, when the mandrel moves in a second direction relative to the housing and opposite the first direction, the hydraulic fluid is metered through the second fluid flowpath and the first fluid flowpath is occluded. a housing; a mandrel received within the housing and movable relative thereto; a pressure chamber defined between the housing and the mandrel and filled with a hydraulic fluid; and a hydraulic lock piston arranged about the mandrel and radially interposing the housing and the mandrel, the hydraulic lock piston including: a pressure piston (214a,b) having a first end exposed to the pressure chamber; a second end; first and second fluid flowpaths (506a,b) defined in the pressure piston (214a,b) and extending axially between the first and second ends (504a,b); a cap arranged at the second end and defining a first exit aperture aligned with the first fluid flowpath and a second exit aperture aligned with the second fluid flowpath, wherein the cap provides one or more cap lobes (522a,b) and the second exit aperture extends axially through one of the one or more cap lobes (522a,b); a valve plate arranged adjacent the cap and providing one or more valve lobes (404a,b) that intermesh with the one or more cap lobes (522a,b); and a bearing ring that mates with the valve plate when assembled on the mandrel, wherein, when the mandrel moves in a first direction relative to the housing, the hydraulic fluid is metered through the first fluid flowpath and the second fluid flowpath is occluded, and wherein, when the mandrel moves in a second direction relative to the housing and opposite the first direction, the hydraulic fluid is metered through the second fluid flowpath and the first fluid flowpath is occluded. a pressure piston (214a,b) having a first end exposed to the pressure chamber; a second end; first and second fluid flowpaths (506a,b) defined in the pressure piston (214a,b) and extending axially between the first and second ends (504a,b); a cap arranged at the second end and defining a first exit aperture aligned with the first fluid flowpath and a second exit aperture aligned with the second fluid flowpath, wherein the cap provides one or more cap lobes (522a,b) and the second exit aperture extends axially through one of the one or more cap lobes (522a,b); a valve plate arranged adjacent the cap and providing one or more valve lobes (404a,b) that intermesh with the one or more cap lobes (522a,b); and a bearing ring that mates with the valve plate when assembled on the mandrel, wherein, when the mandrel moves in a first direction relative to the housing, the hydraulic fluid is metered through the first fluid flowpath and the second fluid flowpath is occluded, and wherein, when the mandrel moves in a second direction relative to the housing and opposite the first direction, the hydraulic fluid is metered through the second fluid flowpath and the first fluid flowpath is occluded.