the pins, if its a pinned one are uni-directional. meaning they only come out one way. smith and wesson is the only one that makes some ar15 drilled the opposite on the front sight base. if you look at each side you will notice one end of the pin is slightly larger than the other.
it takes some effort to knock them loose at times. just makes sure your fully supporting the barrel as you dont want to bend it trying to knock the pins loose.
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