I've finally got round to getting some "metal" pencils!
Ignore the first pencil, I got it years ago and just happens to be in the photo.
The 3 middle pencils are made by Ohto and are aparently all metal except for the plastic tube that holds the spare leads and which connects the click button to the clutch. The barrel is made from aluminium and I guess brass and steel for the bits at the lead sleeve and clutch.
The bottom one is a Rotring 600 which has a brass barrel. Comes in silver or black. The silver is supposedly some sort of plating and is harder wearing whereas the black version is maybe a type of paint and wears off more easily.
The Ohto are:
Promecha 505P £6
This is very light and has a fixed lead sleeve. On my pencil, the lead advance button is loose on the barrel and rattles (fixed with a bit of sellotape), and the lead sleeve is slightly bent (straight but at at an angle to the pencil). The click has a light action and gives a clear and distinct click.
Promecha 1005P £8
This is much heavier and has a "retractable" lead sleeve. The lead sleeve is actually fixed and doesn't move, it's actually the rotating knurled grip that screws up and down the barrel that covers the lead sleeve.
I think this is better than a retractable lead sleeve that moves in and out. Retractable lead sleeves can have wobble at the tip and is an additional complication.
Again, the lead advance button is loose and rattles (fixed with a bit of sellotape). The action is heavier and slightly mushy.
The point of balance is towards the bottom writing end and the grip makes the pencil wider to hold. But the knurling is very smooth and doesn't provide much grip.
Super Promecha 1505P £10
Similar to the Promecha 1005P, about the same weight but has an adjustment to vary the length of lead advanced per click.
I think the click button, lead indicator and clip has a better looking design, the type of clip that just clips onto the pencil looks a bit crap to me.
However there's some downsides compared to the Promecha 1005P. The grip rides on very shallow males threads on the barrel, they're only about 0.2mm deep.
The pencil with the brass threads is the cheaper Promecha 1005P.
The grip is also a loose fit, a bit of tape on the threads removes the wobble and makes it smoother to turn.
And the cutouts for the lead advance adjusting wheel weakens the barrel quite a lot.
The click button is also loose and rattles, on 4 out of 6 examples.
Rotring 600 silver, about £21* (black is usually cheaper)
This feels much more solid. The click feels better with more distinct "click". But the point of balance is at the middle of the barrel and the knurled area is more grippy but narrow and further down, with the pencil at an angle for normal writing your thumb would not be on the knurling. I think I prefer a bottom heavy pencil.
The click button is a very loose fit with a huge gap between it and the barrel. It only rattles a bit though, as I think there's less side to side movement of the spare lead tube inside the barrel. Needs 2 layers of tape to get rid of the gap.
The lead sleeve is fixed, but a Bic Round Stic cap fits and matches perfectly to protect it when not in use.
It's also expensive, double of the Ohto Super Promecha 1505P. Although I paid £16.50.
The box saids "full metal ... pencil" but it has plastic part(s) inside. And made in Japan.
*the price varies quite a bit, black is £17.50 currently on Amazon.