API 16C requires that drilling riser choke and kill systems (P-lines) meet the requirements of NACE MR0175/ISO15156-2. This means a maximum material hardness of 22HRC. Further NACE/ISO15156-2 allows downhole casing tubing and tubular components made of AISI 41xx steels quenched and tempered in tubular form to have a hardness of 26HRC but each heat should be qualified by Sulfide Stress Cracking (SSC) testing in accordance with NACE/ISO15156-2 Clause B.1 using the UT test. Aker Drilling Riser experienced hardness over 22HRC in production of AISI 4130 Q&T choke and kill lines. This article describes Capcis HSE OTI 95-635 full pipe ring sour corrosion tests on high hardness AISI4130 Q&T P-line pipe and weldments. The pipes were loaded by squeezing up to a Hoop stress in the outer surface of 552MPa (SMYS). Test solution was NACE TM0177 solution A with H2S partial pressure of 0.01 0.1 and 1.0 bar respectively. Pipes and welds (weld cap and heat affected zone) with hardness that ranged from 230HV10 to 357HV10 did not show any signs of hydrogen induced sulfide stress cracking after the 30 days exposure. Test procedure and an overview of actual pipe and HAZ hardness variations will be presented. The test results suggest that the present NACE/ISO15156 hardness limits for AISI 4130 Q&T pipe and welds may be too conservative.