Jo, correct me if I am wrong, but I'd assume that the HRC manual is based around an SE/SP model, so I'd imagine the part number HRC quotes is for a head matched to an SE/SP barrel.

The R model has a slightly different barrel, so wouldn't a safer option be to use the R model rear head, just in case?

No right or wrong I think, but something that just struck me looking at my manual.

Andy.
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