So following on from Robert's modern made Britannia update,

http://www.airgunbbs.com/showthread....ia-2021-update

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Bear in mind most surviving Britannia's are doing around 7.5ftlbs. you could maybe get it higher with a stronger spring and fettling but it would probably be a bugger to cock and the trigger would get heavier as the spring got stronger, and adjusting the trigger lighter would just reduce sear engagement etc.

I have a used Britannia which I've given a bit of a tune, (new spring, sleeved transfer port, piston sleeve and fitted spring guide) which is doing 6.8 ftlbs but cocks and shoots beautifuly.

I'm not convinced by old or second hand reports of Britannia's doing '10-12ftlbs' and have yet to hear of these powers being measured on a modern chrono.


Before he got his chrono he adjusted the pressure in the gas ram to be as high as possible, whilst keeping it comfortable to cock it.
He assumed it would be quite powerful.
My Britannia has a stroke length of 75mm and a 28mm cylinder and a swept volume of 46181mm2,
His new one has a stroke length of 85mm, has a 27mm cylinder and a swept volume of 48667mm2 so very similar.

When he finally got his Chrono working it turned out it was doing 7.5ftlbs!
He did say it shot very smoothly with hardly any recoil at all.

I was surprised by this but also reassured that Fred Cox knew what he was doing. Maybe that is the maximum it will comfortably do, with the amount of leverage the barrel and cocking lever will give dictating how powerfull the spring or gas ram can be.

I think slow-runners fantastic Zealandia designs with the cylinder at the rear, but with a two stroke cocking system allowing for a stronger spring, is where the Britannia may have evolved to, if it hadn't gone down the swanny in 1908.

Needless to say I have passed on the Zealandia design ideas to Robert as requested. fingers crossed he gives it a go but that's probably asking a bit much!

interesting stuff, and many thanks to Robert for sharing.

Matt