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Bofors casing thread size question ~

Gspragge said:
Can any one tell me what the primer thread size is in the base of a standard casing.
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The larger Bofors No 18 Mk1 & 2 primers seems to use 1.18" x 14 so try 7/8" BSPP tap. (Brit.Std Para pipe).
Small No 12 primer uses a 5/8" x 18 conduit tap. (same as 2pr Vickers & Tank).
A 5/8 x 18 UNF will work but does remove some metal as 60 degree threads and not 55 degrees.
Primer still screws in ok BUT best to try it first on some brass if you cannot find a conduit tap.
These are my thoughts and I have used both taps on my damaged primer threads. Your choice??
 
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