FWB Sledge vs Giss question?

[Drew451]

Slighty ironic but definately not surprising that the Diana Airking uses the FWB type system .

[dvd]

Slighty ironic but definately not surprising that the Diana Airking uses the FWB type system .

It's probably more to do with producing a recoiling recoilless gun as cheaply as possible. I'm not saying the Air king is cheaply made, just that producing the Giss recoilless mechanism would be very expensive in comparison.

[Geezer]

It's probably more to do with producing a recoiling recoilless gun as cheaply as possible. I'm not saying the Air king is cheaply made, just that producing the Giss recoilless mechanism would be very expensive in comparison.

Especially for a rifle that produces 20 ft-lbs in unrestricted form.

[Garvin]

It's probably more to do with producing a recoiling recoilless gun as cheaply as possible. I'm not saying the Air king is cheaply made, just that producing the Giss recoilless mechanism would be very expensive in comparison.

I think the genius of the Giss Dianas was that their recoilless design was potentially very expensive but they kept the costs down by making a huge quantity of them - in the case of the pistols by having both a fairly cheap budget model (mod 6) and a top-end match model (mod 10) - all with interchangeable parts. Which makes it all the more surprising that Diana dropped the ball so badly when it came to launching the model 75 Giss rifle.

[T 20]

Especially for a rifle that produces 20 ft-lbs in unrestricted form.

25

[Drew451]

It's probably more to do with producing a recoiling recoilless gun as cheaply as possible. I'm not saying the Air king is cheaply made, just that producing the Giss recoilless mechanism would be very expensive in comparison.

Its certainly due to the cost factor. Also the fact that a similarly powered Giss rifle would have to be very long indeed.

[Drew451]

I think the genius of the Giss Dianas was that their recoilless design was potentially very expensive but they kept the costs down by making a huge quantity of them - in the case of the pistols by having both a fairly cheap budget model (mod 6) and a top-end match model (mod 10) - all with interchangeable parts. Which makes it all the more surprising that Diana dropped the ball so badly when it came to launching the model 75 Giss rifle.

The 75 did arrive very late. Although the Anschutz LG380 was later still and is much more scarce.
It would have been interesting if the 75 arrived in the early '70s alongside a range of sidelever Giss pistols.

[Geezer]

25

I think M&G’s official figure is nineteen-point-something in .22”, less in .177”.

Given that the 48/52 comfortably hits or exceeds twenty in “export” form, it makes me wonder whether Diana with the 54 are the first maker ever known to understate an airgun’s power, or whether they’ve done something to the 54s to make them a bit less powerful because that works best with the sledge?

Similarly, I wonder about how well the sledge would work if you properly de-tuned the action to make 11.a bit. I assume that U.K. spec factory models just rely on a TP restrictor, giving an inefficient action with plenty of surplus energy to work the slidey thing. What would happen if you increased the efficiency of the action to generate sub-12 m/e (short-stroke, sleeving, etc), while decreasing its total energy? Would the slidey thing still work properly?

[Geezer]

Its certainly due to the cost factor. Also the fact that a similarly powered Giss rifle would have to be very long indeed.

I don’t think the Giss system would be practical at 12, let alone 20. As you know, Giss only uses the forward piston to propel the pellet. More powerful twin-piston designs (Whiscombe, Park) use both.

[T 20]

I think M&G’s official figure is nineteen-point-something in .22”, less in .177”.

Given that the 48/52 comfortably hits or exceeds twenty in “export” form, it makes me wonder whether Diana with the 54 are the first maker ever known to understate an airgun’s power, or whether they’ve done something to the 54s to make them a bit less powerful because that works best with the sledge?

Similarly, I wonder about how well the sledge would work if you properly de-tuned the action to make 11.a bit. I assume that U.K. spec factory models just rely on a TP restrictor, giving an inefficient action with plenty of surplus energy to work the slidey thing. What would happen if you increased the efficiency of the action to generate sub-12 m/e (short-stroke, sleeving, etc), while decreasing its total energy? Would the slidey thing still work properly?

IIRC Bigtoe did some experiments many moons ago and found that the 54 sledge still worked with a reduced piston stroke and he also found the sledge system moved by a reduced amount.

From a power point of view, from what I can gather the early D54 T01 has a longer stroke than the later D54 so could explain the 25ftlbs I recorded from a 54 T01 --- or maybe it was a made on a Monday morning gun.



All the best Mick

[T 20]

I don’t think the Giss system would be practical at 12, let alone 20. As you know, Giss only uses the forward piston to propel the pellet. More powerful twin-piston designs (Whiscombe, Park) use both.

The original Giss patent had the Pistons travelling towards each other, this is said to be where John Whiscombe got his inspiration from. :-

image.jpg



All the best Mick

[airgunwerks]

I have shot and rebuilt literally hundreds of both over the last 39 years and a serviced Feinwerkbau will always outshoot the 75 in a experts hands, if either is neglected the FWB will survive but if the 75 is shot with bad seals the teeth on the rear of the pistons will break off and you may end up with a door stop. Build quality on the Feinwerkbau is superior in every aspect.

[dvd]

I have shot and rebuilt literally hundreds of both over the last 39 years and a serviced Feinwerkbau will always outshoot the 75 in a experts hands, if either is neglected the FWB will survive but if the 75 is shot with bad seals the teeth on the rear of the pistons will break off and you may end up with a door stop. Build quality on the Feinwerkbau is superior in every aspect.

That's true since serviceability and simplicity are very important when competing at the top level.That, and having a production facility focussed on precision airguns, goes a long way to convincing users that they have the best product to compete with.
My FWB 300 buzzes slightly and I could easily fix that but it's accuracy is still astounding, so I leave that alone because it's not too detrimental to the gun. That's the effect of simplicity in design.
I agree that the Achilles's heel of the 75 is the seal, when that goes out of spec, the timing goes off and the idler gears become loaded, leading to unbalanced forces and problems.
Having said that, one of the best party tricks I love to do with the Diana 75 is to stack 5 flathead pellets on top of each other on the action and pull the trigger. They stay put
There's nothing like a well fettled Giss action subduing a springer.
Perhaps the other closest and more equitable competitor to the FWB 300 is the Anschutz 380, which also utilises the sliding action mechanism, but inside a fixed action. That is another marvel of engineering.

[Ian Cartmell]

I’m currently shooting a 300s and 65 in a 66 stock out to 25 yds.
Both scoped although the results with a diopter are almost as good.
The 65 just edges it in my hands for consistent grouping, zero recoil as opposed to the very slight nudge of the 300.
Over 10 metres or 6yd bell with a diopter I once again find the 65 to be more consistently accurate in my hands
This is only my findings but the 300 is my favourite to shoot.

[DrGunn]

IIRC Bigtoe did some experiments many moons ago and found that the 54 sledge still worked with a reduced piston stroke and he also found the sledge system moved by a reduced amount.

The sledge system works by allowing the centre of mass of the gun to remain stationary during the firing cycle - the heavy action moves backwards a short distance as the lighter piston moves forward a greater distance. Either making the piston lighter or reducing the stroke will reduce the sledge travel.