When you buy a new Glock pistol, and field strip it for the first time (before shooting it), you may notice a copper colored grease on the slide rails. If you wonder what this is (and I did) it is loctite C5A anti-seize. This is a factory anti-seize co0mpound that serves a couple of purposes. The first is for those that buy a new gun and do not clean and lube it before shooting it (pretty much a no-no). Being a grease, the anti-seize compound is better for long term storage than an oil because oils tend to migrate and evaporate while a grease will stay in place longer.
The other reason they use the anti-seize rather than a straight grease is that it is slightly abrasive and can help the frame and slide mate together. This isn’t all that noticeable but the manual that comes with your new glock clearly says:
CLEANING THE FIELD STRIPPED PISTOL
SLIDE.The slide rail cuts should be cleaned of dirt and debris by using a clean patch on the end of a
toothbrush-type cleaning tool. Note that the copper colored lubricant found on portions of the slide of
brand new GLOCK pistols should not be removed, as it will help to provide long-term lubrication of the
slide. The breech face and the area under the extractor claw should be held muzzle down and cleaned
with a toothbrush-type cleaning tool, and should both be absolutely dry and free of any dirt or debris after
cleaning. All other exposed areas of the slide should be checked for cleanliness, and wiped or brushed
They do teach in the Glock armorer school that cleaning off the anti-seize and replacing it with a proper lubrication job is fine, just as it is still okay to just leave it on the gun and shoot it as it comes from the box.
I cleaned mine off, so I don’t know how long it would last until it was removed by wear, but I have been told it only lasts about 200 rounds.
I will tell you that it is not the best gun lube on the market, but it stays put, and if your going to store a gun more that you shoot it, and expect it to fire without being cleaned first (again – not the best option, but nightstand guns come to mind), then this may be an option.
Additionally, this works pretty well on removable shotgun choke tubes, as it is designed to protects mating parts and provides a shield against high temperatures seizing and galling.
Loctite C5-A Copper Based Anti-Seize, exclusive formula suspends copper and graphite in a high quality grease. Protects metal parts from rust, corrosion, galling, and seizing at temperatures to 1800F (982C).