I have got just over 100 shots through my New Knight Mountaineer .45 Cal 1:20 Twist, I have been keeping a close eye on this Lehigh Vent Liner for wear, This 17-4 Stainless Liner has NOT budged! It was right at .030 when i got it, and it has stayed there for over 100 Shots of BIG Lead, and Fairly heavy Powder Charges. As some of you know, BIG Lead, and Big Powder Charges (400 Grain Bullets and Heavier, Pushed by 80 Grains of Powder) Will Tell on a Weak Flash Hole in a HURRY, If the Material is not REALLY Durable it will FAIL quickly under these Conditions. This Lehigh Vent Liner is HANGING ON STRONG!! I will definitely be getting some more of these to keep on hand. Kudos to Lehigh Defense

COPIED AND PASTED FROM LEHIGH

The vent liner is produced from 17-4 stainless through hardened to Rc38 - 48 and then gas carbonitited to achieve a surface hardness of Rc60. This high surface hardness reduces wear from flame erosion extending the useful life of the vent liner. Replacement is recommended when the flash hole erodes to 0.038 or if velocity loss is recognized.We advise a drop of oil, or preferred, a quality lithium or molybdenum disulfide grease be used on the vent liner threads upon installing into the breech plug body. The vent liner fits all Lehigh and Savage MLII breech plugs using removable vent liners.