HW77/97 barrel length

Discussion in 'Piston & Spring' started by Cooper_dan, May 30, 2018.

  1. Cooper_dan

    Cooper_dan Active Member

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    I'm very much a newbie when it comes to Weihrauch's but I do fancy a blue laminate one.
    Choices are the HW97k blue laminate that we get in the UK, or get one from Germany where they seem to do all options in the blue laminate stock. There is also a cost saving from Germany, even with the cost of a new spring. So the choices are:

    97k = 300mm barrel
    97 long = 385mm
    77k = 370mm
    77 long = 470mm

    Has anyone had experience with all the barrel lengths? How much difference do they make?
    (p.s I'm not fussed about weight. The heavier the better with me)

    Thanks!
     
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  2. skires

    skires Well-Known Member

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    Hi Dan

    I'm not sure if this is what you are asking ...

    There was an opinion a few years back re barrel lengths on HW underlevers. The preferred length for target shooters running 0.177 guns at the usual 780 fps ( Exact ) was a length around that 385mm. The original 97's had that slightly longer barrel than the more recent UK 97k.

    Tony Wall ( Sandwell Field Sports ... a Marmite story in the airgun springer world ) started selling a 97 that was aimed at 0.177 target shooters ( Probably HFT ). He was labelling it and selling it as a super rifle that was specifically made by SFS. It was actually an earlier style, longer barrel, 97 action that he bought in from Germany, and then tuned and sold for decent money.

    The 'not fussed about weight' thing ... I don't think it's about weight as much as balance and feeling right on aim. I've had mostly the 77K with the 370mm barrels. I've removed the front latch and fitted heavy steel silencer units ( like the Venom ). That, for me adds far too much weight to the front end of the rifle and I feel one then has to add plenty of weight at the back of the stock to get the balance right again. Some people like that overall addition to weight. I'm not convinced that it really helps all that much compared to having a rifle that may be a tad lighter but the shooter feels it handles better.

    The rest is down to stock preference. The 77 is designed for iron sights and has that lower cheek. The 97 stock was then designed for scope only use. Some prefer the 77 low cheek stock and use a chin on cheek piece contact. You are obviously going to keep it in the original stock as you are specifically talking about liking the blue laminate. What are you going to use it for? If it's HFT then any standard stock will have too shallow a fore end unless you shoot hand slightly up the peg.

    Looks wise ... that's your preference. Do you like the slender look of the 77 stock? Do you like your springers to be short and very carbine like, with the under lever ending at the same point as the end of the 'silencer' or front latch?

    Practical wise ... If it's for scope use I'd go for the longer ( original length ) 385mm barrelled HW97 from Germany.
     
  3. oyster

    oyster Member

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    Hi, I would echo Skire's summary as above, I have had almost all the variants and can advise my personal favourite (currently) is the HW97K with the green laminate stock, similar but different shade to the centenary model. I have realised that even the various coloured laminates, as well as the many beech stocks, all have a slightly different handling. That green one is one of the heaviest and holds the action well. The HW77 has a longer lock time due to its barrel length so requires a more subtle deliberate hold when firing. In .22 it will have the softer firing cycle than the HW97 if it is set up properly.
     
  4. Adam

    Adam Active Member

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    Difference is negligible, fraction of a millisecond.
     
  5. hmangphilly

    hmangphilly Not quite a full phil

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    Frillisecond
     
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  6. Nomads HFT

    Nomads HFT Active Member

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    Around 0.3 milliseconds (HW97 long/short barrel) to 0.4 milliseconds (HW77 long/short), in a total time to pellet exit in the order of 11 milliseconds.
     
  7. RobF

    RobF Administrator Staff Member

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    Blink of an eye 50ms

    Human reaction time 500ms

    Conscious decision time delay behind subconscious decision time 1000 - 7000ms
     
  8. skires

    skires Well-Known Member

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    7000ms is 7 seconds.
     
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  9. Nomads HFT

    Nomads HFT Active Member

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    Recent research suggests that the brain stops processing information from the eyes throughout the entirety of the blink process of 100ms to 150ms, Rob. That's relevant to target shooting, because blink and you miss in the region of 20 to 30 yards of a pellet's flight, and may explain why on some occasions we fail to see a pellet in flight, but do see it on others.

    https://phys.org/news/2005-07-brain.html
     
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  10. RobF

    RobF Administrator Staff Member

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    Also interesting is the brain doesn’t process as the eye moves. You can test this, look straight in the mirror at one of your eyes. Now look at the other one. Not only do you not see a blur as your eyes move across but you also will miss most of the movement of your eyes in the reflection. You only see the image once the movement is over.
     
  11. Sake-San

    Sake-San La Vieille Alliance

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    Reverting to the op, do the longer barrels not make power easier (less spring effort required)?.
    A potential consideration for tuning flexibility, especially for those embracing the current vogue of soft & fluffy tunes.... just a thought.
     
  12. Nomads HFT

    Nomads HFT Active Member

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    I didn't know that, Rob. Every day's a school day on here.

    An interesting question. Gerald Cardew measured pellet acceleration only as far as 5" up the barrel, John Bowkett and David Robson independently measured pellets accelerating the full length of 16" barrels, and all three measurements are sound, so why the discrepancy? Cardew's measurements were with a very short piston stroke, low swept volume rifle, so had little time to accelerate and too little air, while John and David's results were with longer stroke rifles with more swept volume, giving a longer acceleration period.

    Problem is, both John and David's tests were in .22", and I am not aware of anyone conducting the same test with .177", so it's by no means certain that a .177" pellet will gain from a longer barrel (unless anyone knows different).
     
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  13. RobF

    RobF Administrator Staff Member

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    We were going to take a rifle with a 16" barrel and simply cut an inch off and chrono... it's on the list..
     
  14. Nomads HFT

    Nomads HFT Active Member

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    That would answer this particular question nicely, Rob.

    On my list is to get hold of a 16" .177" barrel machined to fit a TX200, to cut it by increments, measuring the muzzle velocity of a range of pellets as I go, but at each length using two cylinder/piston/spring/preload combinations that give different piston strokes.

    It would be nice, to say the least, to be able to map pellet position against piston position for a range of pellets and piston strokes.
     
  15. Cooper_dan

    Cooper_dan Active Member

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    This is the crux of it really.
    Swapping my 25mm dia, 84mm stroke internals from my TXHC to TX mk3 increases muzzle energy by about 0.5 ft-lb

    If the benefit continues up to the full length 77 I could be very interested. Softer firing cycle and more weight = win-win
    I think I can get a 25mm HW97 piston to go in it too. I'm a big fan of OEM parts done well
     
  16. Cooper_dan

    Cooper_dan Active Member

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    I'm wondering if it would be possible to build a simulation model that would approximate this. I've got the use of some very good mechanical/hydraulic/pneumatic simulation software. Would just need some measured values to correlate the model. Possibly the TX mk3 and HC using the same internals with just the barrel length as a variable
     
  17. Nomads HFT

    Nomads HFT Active Member

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    Plenty of people already have, Dan. The first simulation model I'm aware of was in 1985 by a chap by the name D. M. Owens, then a year or so later by a dozen post graduate engineers during their induction year at a huge multinational company that afforded them unlimited computer and laboratory time both sides of the Atlantic.

    Many more have joined in in recent years, but all have lacked essential data. As a 'for instance', until I measured pellet start pressure three years ago, the only available data was somewhere between 250-400psi, so models at the time for any pellets that had lower or higher start pressure (JSB and RWS respectively) were flawed and, to make the predicted muzzle energy match the measured energy, 'factors' had to be introduced, which an unkind or mischievous person might call 'fudges'. :D

    There's still a lot we don't know. If I could map pellet acceleration against piston position and a model could be 'factored' to match that, it would be more accurate, but only for that rifle in that state of tune with that pellet.
     
  18. Adam

    Adam Active Member

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    On the one hand, there is 50% more volume in the same length of .22 barrel vs .177, which should imply there's more than enough air to keep accelerating the .177 pellet through a long barrel. On the other hand the same pressure can exert 33% less force on the reduced area of the .177. On the third hand, the .177 pellet is around half the mass of the .22 pellet. :)

    I used have a CO2 powered Umarex Smith and Wesson 586 replica with a 6" barrel. I had a .22 conversion made from an offcut of Crosman barrel. Accepted wisdom says the .22 is more efficient than .177 so you would expect power to increase. It didn't, it actually went down slightly. I put this down to the valve size, the gas tube diameter and the hammer weight and spring were optimised to be reasonably efficient for .177 and to give a decent shot count, and simply didn't release enough gas to drive the .22 pellet at the same energy.
     
  19. MickyFinn

    MickyFinn I❤HFT

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    Dan my full length 77 is definitely softer (even now its a 26mm piston) than the 3 97k (in various states of tune) + 77k i have.
     
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  20. hmangphilly

    hmangphilly Not quite a full phil

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    He makes it all up .

    You do know that don't you Jim ?
     

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