Fpe increase from 4inchs of barrel on a theoben rapid

Discussion in 'General Airgun Chat' started by 211anthony, Oct 9, 2013.

  1. 211anthony

    211anthony New Member

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    What increase of fps or fpe could I expect from 16 to 20inchs on my theoben rapid and when replaced and detuned back to under 12fpe what shot count increase would I expect?
     
  2. Conor

    Conor Never been banned from sales Staff Member

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    Ardboe, Co.Tyrone.
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    Back Hill Ballistics; DFTC; Nelson FTC
    You can achieve 1ft/lb per inch of barrel so potentially 4ft/lb increase.
    Shots per charge depends on caliber but perhaps 25 shots at a guess.
     
  3. 211anthony

    211anthony New Member

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    .22 cal and thanks for the reply
     
  4. Tench

    Tench WHFTA World Champion 2016.

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    There is no hard and fast rule that can be applied to all PCP's, it comes down to the exhaust valve duration of your particular rifle. For example, if your exhaust valve is still open when the pellet leaves the barrel you would see a big benefit in power or shot count from using a longer barrel, or if your valve is closed long before the pellet left then you may even see a reduction in power and shot count from a longer barrel, i have witnessed both scenarios. The likely hood of seeing a significant shot count increase changing from a 16" to a 20" barrelled .22 at 12 ft/lb is slim.

    Simon.
     
  5. 211anthony

    211anthony New Member

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    Thanks not worth the money by the sounds if it! Thanks for the replies.
    Anthony
     
  6. Rhys

    Rhys Member

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    Are you trying to run this sub 12 ft lbs or is it FAC?
    Set up wise, i am running a TTR1 with a 14 inch barrel, reg set at 1500psi not the manufactures recommended pressure which is higher, (.177) and i can achieve way over 100+ shots before i even hit the 100 bar reg pressure even from a 280cc bottle.
    Rapids are really easy to set up right, but a few more details, i.e model, reg'd or un regged, internal set up etc and it can be run correctly in no time at all.
    Actually just noticed you are in Cardiff, if you fancy a trip to Llanelli at any point, i can set it up with you if that helps?

    Regards,
    Rhys
     
  7. 211anthony

    211anthony New Member

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    Thanks for the offer mate but it's already been tuned and fettled ;)
    Custom carbon sleeve and silencer
    Cs800 mfr stock with 280cc bottle
    Bushnell 5-15x40 scopes
    ;) just thought I'd be greedy and get a bigger barrel for more shots because I had to change the bottle from a 400cc to fit my new stock which iv just sanded and oiled with rapid oil and I'm very proud how it's turned out :):)
     
  8. Rhys

    Rhys Member

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    No probs,
    As said above, more gain to be had off balancing the reg and hammer set up...plus it won't be 100 miles long!
     
  9. Charlts

    Charlts Getting dusty

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    If you change the barrel it'll need doing again, bolt on bits with exception of bigger buddy bottles won't gain you any shots.
     

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