All,
I've just received two SMLE bolt heads. Both are marked M261 and have an S stamp as well (S for spares?....and are long length....0.640"). They are of the malleable cast iron type (I think....not the more modern looking silverish type with the M stamp) and have the 0.020 chamfer only on the left edge of the bolt face. I think these are WW1 era bolt heads and were replacement parts (S stamped).

Here's the question:
What is the extractor screw thread supposed to be on these bolt heads? None of my standard (BA5?) cheesehead extractor screws from other SMLE or No1 bolt heads or new ones from the spares box will thread into these two boltheads...they bind up after a thread or so of engagement. Are these boltheads supposed to have 5BA threads for the extractor screw? As an aside, I gently tried a standard 4/40 screw and it theaded (loose engagement) and did tighten up. Do I simply need to chase the threads with a 5BA tap or are the threads different and I need a different extractor screw?
Thanks!
GC
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