Bonehill britania springs...?

[Shed tuner]

just stripped mine...

There is an inner spring, which sits on a flared section of the guide, and passes into the body of the piston
There is an outer spring, actually comprised of two springs, with a 3/4" spacer collar, which bears upon the rear of the piston and the end of the guide.

The piston itself is mostly machined away by virtue of large slots.

Is this arrangement original ?

[Shed tuner]

So just overhauled this quickly, as it's new to me...

- the breach seal was toast, so I made a new seal with a couple of hole punches, a big hammer, and an old leather belt. Job done, perfect thickness
- piston head was also toast, so I made a nylon o-ringed head for it. There's still over 1/2" of clearance from the cocking link, so I will probably replace this with a diana 28mm parachute seal, which will gain another 1/4" of stroke, for more power and a softer cycle Or even a BSA standard type leather seal.
- the spring arrangement (1 skinny and 2 short/fat) was just silly, so I found a suitable skinny spring and did away with the lot. This new spring was a medium wind, 3.0mm wire, and gave about 1.5" of preload. Cocking effort was moderate, but not silly low, so seemed about right.
- just did a general moly relube in all the obvious places, and re-assembled

After a dozen or so shots, it was behaving quite nicely. Fast firing cycle, just a fraction harsh, but nothing unpleasant. Just for curiosity I checked the power - 5.5 FP on low power, and 7.5 on high. I'd expect that to come down a smite as there's a little combustion, but if I want more power I'll change to the seal as described above.

Overall very pleased, and impressed with this baby.

Only big decision I have left is whether to refinish it or not - it's on that line between whether it's too tatty as is or will it be devalued by a refinish... most likely I'll leave it as is and just enjoy it. Nothing like renovating and enjoying shooting a 110+ year old gun

[Benelli B76]

Jon, I have only stripped one of these to make a new PU piston seal for it and it had a standard type single spring setup with its normal piston. I found this pic on the net which must be similar to your Brittania.

Baz

[micky2]

Yes they should have just one spring, l would leave it as is and not restore it as l don't think it adds value and it takes away it's history. is it the 1st or 2nd pattern ?. see Hillers book if you have it. whats the se/no.
Mick.

[Shed tuner]

yeah, I found that same pic.. but here's the thing - why have that step half way along the guide and just waste all that cylinder / spring room ?

Mine looks like that, but with the additional outer springs.

Need to check hilliers book, didn't even realise there were two variants (ignoring rearsight changes).
I think I will probably leave unrestored/

[Josie & John]

Definitely one mainspring originally Jon

Kind regards,

John

[Shed tuner]

thaniks - so the question remains - why the flare halfway up the guide, that wastes all that spring room ?

[draitzer]

The flange halfway up the rod is the spring stop. If it weren't there, you'd need a spring about twice as long (and consequently much thicker wire) to get the force required.

Don R.

[Shed tuner]

The flange halfway up the rod is the spring stop. If it weren't there, you'd need a spring about twice as long (and consequently much thicker wire) to get the force required.

Don R.

yes and no.... you'd certainly need a spring about twice as long, but why thicker wire so long as it;s properly supported by the guide ? A longer spring creates a more uniform acceleration, a shorter one far more acceleration at the beginning of the stroke than at the end. This is largely why FAC designed guns with a lot of spring room, when properly converted to 12 Fp (e.g. sleaved down HW80s and Pro Elites) shoot so nicely.

And if they wanted to use a shorter spring, why not have a shorter cylinder, and save some weight ?

/starts searching the bay for a bonehill rear guide/end cap that I can machine to take a better suited spring...

[greenwayjames]

The stop on the rod for the spring to sit on is how they were as others have said. Probably not worth Bonehill changing from the original guns he imported form Germany and rebadged as Britannias. Perhaps they knew more over 100 years ago than we think we know now

[draitzer]

yes and no.... you'd certainly need a spring about twice as long, but why thicker wire so long as it;s properly supported by the guide ? A longer spring creates a more uniform acceleration, a shorter one far more acceleration at the beginning of the stroke than at the end. This is largely why FAC designed guns with a lot of spring room, when properly converted to 12 Fp (e.g. sleaved down HW80s and Pro Elites) shoot so nicely.

And if they wanted to use a shorter spring, why not have a shorter cylinder, and save some weight ?

/starts searching the bay for a bonehill rear guide/end cap that I can machine to take a better suited spring...

If you kept the same number of coils in your twice-as-long spring, then wire diameter would remain as is. I was expecting the coil spacing would be kept as-is, which would give twice the coil count, hence lower spring rate and the need for thicker wire. By the way, in some cases at least, shorter springs are favored for a less traumatic shot cycle - e.g., in the U.S., Jim Maccari's FWB 124 kits have considerably shorter springs than original and get rave reviews.

Don R.

[Shed tuner]

If you kept the same number of coils in your twice-as-long spring, then wire diameter would remain as is. I was expecting the coil spacing would be kept as-is, which would give twice the coil count, hence lower spring rate and the need for thicker wire. By the way, in some cases at least, shorter springs are favored for a less traumatic shot cycle - e.g., in the U.S., Jim Maccari's FWB 124 kits have considerably shorter springs than original and get rave reviews.

Don R.

Ahh, sure, then yes, of course... or a narrower diameter, or whatever else to increase the stiffness.

Short vs long depends on preload really - Jim did an excellent article in AGW a few months back on this - not sure if you get it in the US ?

Peronally I'm not a fan of the shorter spring kits in the FWB, but Jim's seals can be quite good.