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Old 07-20-2009, 01:08 PM
Spotteddog Spotteddog is offline
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Join Date: Aug 2005
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Thumbs up How long do Tritium sights "last"?

Every so often, I see someone ask the question. Sometimes it can't be answered because a gun has been either sold/traded/stolen during the time frame it would have taken to determine just "how long" they do last? In other cases, it may be because the sights haven't been owned long enough to have reached their operational life span. In my case, I have three examples that are now (1)11 and (2)12 years old. For those that don't know what they are, they're a glass vial filled with Tritium gas (an isotope of Cesium, IIRC?) that glows 24/7 without exposure to light sources. In advertising and warranty info manufacturers typically warranty them for between 10 and 13 years. The 4 sets I have (3 old, 1 new) are now able to be compared for brightness. Life span being expressed is called "half life". It's the amount of time the isotope takes to decay to 50% of it's original value. The 3 old sets are all Meprolite S&W revolver adjustable sight sets. The "new" is a set of newly purchased Novak's with Trijicon vials on an M&P9c.
Exactly as listed at the end of 10-13 years in warranty info, the old sight set vials are one half the brightness of the new unit. This was checked in a totally dark room, after 15 minutes of vision acclimation with all 4 weapons lined up beside one another. They're still usable, just not as bright as one may like.
So now, I'm off to order new Meprolite sets for the S&W revolvers wearing them around here.
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