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You'll have to be more specific about the barrel. There are fixed sighted guns, (tapered barrels,) bull barrels, longer barrels & shorter ones.
If your gun has a screw on front sight,,, then a replacement is fairly easy.
What type do you have & what type do you desire?
Black on black sights can be difficult to pick up under adverse conditions. I've installed inserts like this on front sights going back to the Smith & Wesson revolver days when LEO's carried model 19's & 27's in .357 Magnum.
Steel or plastic.
The plastic one comes standard on the "Camper" model Buck Mark. http://www.midwestgunworks.com/page/mgwi/prod/buckmark-front-sight/B5152607
The "Standard" Buck Mark front sight is made of steel. It's slightly shorter in height compared to the plastic one. http://www.midwestgunworks.com/page/mgwi/prod/buckmark-front-sight/B5152689
I've used both without issue. That's a plastic one on the 22/45 above (I like the plastic, because it never gets shiny).
Here is the steel version on some of my Buck Marks:
...and found a photo with the steel Buck Mark sight on my 4" 22/45:
Personally, I like the MKIII front sight. Here's one that I put a white dot on (currently on my buddy's 6" Pac-Lite upper):
Since, I'm posting photos, the HiViz Ruger Mark II/III and Browning Buckmark front sight probably deserves some exposure: