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I would like to tighten up the headspace on an SMLE I have, ideally I need to fit a slightly longer bolt head and that made me think about the 'S' marked SMLE bolt heads, has anyone ever come across one?

I don't recall ever having seen one but I have a box full of bolt heads at home that hasn't been rummaged through.

I believe the "S" bolt heads were over size so that they could be fitted for head space by polishing.

Away from my references at present so that is the best I can do.

'S' marked bolt heads are Spares and are oversize and need to be polished down to size to ensure correct head space. SMLE bolt heads were each individually fitted to a rifle and there fore do not come in a different sizes like the No4.
Your rifle has had it bolt head replaced at sometime, possibly by the unit armourer after re-barreling which is why it has an S on it.

Steve, I have a standard bolt head and need to fit a slightly longer one, hence asking about the S marked bolt heads.

ovenpaa wrote:Steve, I have a standard bolt head and need to fit a slightly longer one, hence asking about the S marked bolt heads.

My mistake, thought you had an S fitted. To adjust you headspace you will need to measure your bolt head and then find one that is longer or if you have a S bolt head polish it down to achieve the headspace that you require but you knew that already. Fultons have probably got a bucket of bolt head, if you ask Colin or Robert they may be able to find an S marked one for you. You could also try EFD for one.

The bolt head must also fit correctly for index - the angle by which it rotates past the main locking rib should be no more than about 5o. New bolt heads tend to increase this angle as the wear in, so the overwhelmingly best option is simply to go through a bucket of used bolt heads and find one that both indexes and meets the headspace requirement (and the manufacturer, if you are restoring something collectible!).

Of course the rifle has to be re-proofed after the new bolt head is fitted.

Just out of interest my SMLE bolt head is stamped with a 'U'. What does that stand for anyone?

farmer7 wrote:Just out of interest my SMLE bolt head is stamped with a 'U'. What does that stand for anyone?

According to my book on Smellies the U stands for (also "M" sometimes) on the bolt head "Difference in specification" and refers to the dimension of the bolt-head, not to anything else.

Basically when your rifle was first put together they used parts that were on hand.

Blu

IIRC the U and the M just referred to the steel type used. There were at least two approved variations to the original materials design spec.