1. If the weapon is dismantled by the purchaser or by third parties further than described in this user's instruction, and if, as a result of inappropriate handling or incomplete reassembly,damage or malfunctions are caused, as a result of which the safety devices are rendered ineffective, the the purchaser shall forfeit any clam to guarantee against damages thereby incurred to persons or property.
2. Any change to the basic construction of the weapon, in particular by the circumvention of the safety devices, is strictly prohibited for safety devices, is strictly prohibited for safety reason, and precludes the use of the weapon.
Based on Magnuson-Moss Warranty Act, GLOCK Inc. offers no express warranty on its product line. However, GLOCK Inc. recognize its obligation concerning implied warranty. GLOCK Inc. products will be serviced for a period of one year from date of retail purchase, for defect in materials or workmanship, at no charge to the purchaser. Be sure to retain your slip as proof of purchase date when making a claim.
Could they deny a warranty claim on the barrel? Probably. Would they? Unlikely. As for the rest of the gun, if it's unaltered, then the warranty will, most likely, remain intact. People that have sent their guns in for work, with aftermarket parts in them, have said they've gotten the gun back returned to stock; some got their aftermarket parts back in a bag with the gun, others did not.
They guarantee the barrels for 40k rounds. That's straight from the mouth of an armorer at Glock corporate. Removing the finish has no affect on function, and there are very few things that can go wrong with a barrel; most of which are going to be immediately evident, not show up 10k rounds later.