No matter what you do, it won't look the part.
That, alone, can be grounds for disqualifying it, if you get a judge that wants to be a jerk.
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CASS/SASS/WEASS/WASA/SASA/COWS/WETF rules drive me nuts.
Among other complaints, "No receiver sights" is purely a cosmetic rule. No basis in history or tradition, just movies and false nostalgia. Receiver sights predate the majority of the rifle models being used in matches today, as well as the cartridges of choice.
I guess it shouldn't bug me, though. The point is not the shooting. Rather, it is all about dancing around in costume, while pretending to have a purpose.
"NO RECEIVER SIGHTS OR FEATHERED COWBOY HATS!!!"
--> Steps up to the firing line in a costume sewn in India, wearing Taiwanese shoes, carrying a Chinese-made smart phone, with a Brazilian-made, 2021 production Rossi 1892 in .357 Mag, shooting smokeless Serbian ammo with an Italian headstamp, at targets twelve feet away (made in Vietnam), to pretend to be an "Old West" cowboy.