Page 3 of 4 FirstFirst 1234 LastLast
Results 31 to 45 of 58

Thread: I don't believe a TP smaller than 3.0mm ever works in a 12FP springer....

  1. #31
    Join Date
    Apr 2002
    Location
    Near Wimbledon, SW London, or Lusaka, Zambia
    Posts
    26,322
    Quote Originally Posted by T 20 View Post
    The first British built Magnum springer of the 1970s, the Webley Vulcan, had a 2.5mm transfer port.

    I've used 2.5mm ports on a number of guns without problems.
    as you know I'm not saying it doesn't work, just that it's not optimal...
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  2. #32
    Join Date
    Apr 2002
    Location
    Near Wimbledon, SW London, or Lusaka, Zambia
    Posts
    26,322
    Quote Originally Posted by look no hands View Post
    How do you us one inside the cylinder?

    Pete
    I have an extension socket with a holder for it. Plenty long enough
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  3. #33
    look no hands's Avatar
    look no hands is offline Even better looking than a HW35
    Join Date
    Apr 2003
    Location
    Coventry, even closer to Tony L.
    Posts
    11,979
    Quote Originally Posted by Shed tuner View Post
    I have an extension socket with a holder for it. Plenty long enough
    Oh you lucky lucky bas****

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

  4. #34
    look no hands's Avatar
    look no hands is offline Even better looking than a HW35
    Join Date
    Apr 2003
    Location
    Coventry, even closer to Tony L.
    Posts
    11,979
    Well I've been playing around with one of my BSA Challengers today and thought I'd measure the transfer port whilst the barrel was off, well the length is 13mm and diameter is 3.3mm, I bought some extra long drills the other day ranging from 3mm to 4mm., so it would be interesting to see how efficient those measurements are for that rifle.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

  5. #35
    harvey_s's Avatar
    harvey_s is offline Lost love child of David Niven and Victoria Beckham
    Join Date
    Apr 2008
    Location
    Norwich
    Posts
    9,319
    No mention of calibre...does it not influence the optimum size of TP required?

  6. #36
    look no hands's Avatar
    look no hands is offline Even better looking than a HW35
    Join Date
    Apr 2003
    Location
    Coventry, even closer to Tony L.
    Posts
    11,979
    Quote Originally Posted by harvey_s View Post
    No mention of calibre...does it not influence the optimum size of TP required?
    Sorry .22 with a 10" barrel.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

  7. #37
    Join Date
    Apr 2012
    Location
    Bristol
    Posts
    6,259
    Get yourself a cheap pin vice and hammer a long steel rod up the back end. Make sure you wrap the widest part in tape so it doesn't scratch the inside of the cylinder.

  8. #38
    Join Date
    Jun 2011
    Location
    Hatfield Broad Oak, Essex/Herts CM22
    Posts
    3,967
    Been out of the game for a long time now and can’t find any of my old notes on 77k with a 25mm piston. What’s the best starting place for these? 3.6mm springs to mind but I don’t trust my memory lol. .22 if that maters...

  9. #39
    harvey_s's Avatar
    harvey_s is offline Lost love child of David Niven and Victoria Beckham
    Join Date
    Apr 2008
    Location
    Norwich
    Posts
    9,319
    Quote Originally Posted by look no hands View Post
    Sorry .22 with a 10" barrel.

    Pete
    I wasn't referring to your post specifically just the OP's theory in general.

  10. #40
    look no hands's Avatar
    look no hands is offline Even better looking than a HW35
    Join Date
    Apr 2003
    Location
    Coventry, even closer to Tony L.
    Posts
    11,979
    Quote Originally Posted by harvey_s View Post
    I wasn't referring to your post specifically just the OP's theory in general.
    Oops!

    And there's me thinking you cared

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

  11. #41
    Join Date
    Apr 2002
    Location
    Near Wimbledon, SW London, or Lusaka, Zambia
    Posts
    26,322
    Quote Originally Posted by brucegill View Post
    Been out of the game for a long time now and can’t find any of my old notes on 77k with a 25mm piston. What’s the best starting place for these? 3.6mm springs to mind but I don’t trust my memory lol. .22 if that maters...
    holy revival - bruce is back from the dead - long time mate, how are you ?

    Start with 3.4 and test
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  12. #42
    Join Date
    Jun 2011
    Location
    Hatfield Broad Oak, Essex/Herts CM22
    Posts
    3,967
    Quote Originally Posted by Shed tuner View Post
    holy revival - bruce is back from the dead - long time mate, how are you ?

    Start with 3.4 and test
    thanks Jon, nice to be back 3.4mm it is.....

  13. #43
    Garry's Avatar
    Garry is offline I scrolled the page up too fast and it fell off
    Join Date
    Jul 2008
    Location
    Birmingham
    Posts
    8,889
    I know nothing about this subject as my following question will indicate

    I'm assuming the transfer port is directly behind the pellet, so why aren't the ports the same size as the pellet calibre?

  14. #44
    Join Date
    Apr 2002
    Location
    Near Wimbledon, SW London, or Lusaka, Zambia
    Posts
    26,322
    Quote Originally Posted by Garry View Post
    I know nothing about this subject as my following question will indicate

    I'm assuming the transfer port is directly behind the pellet, so why aren't the ports the same size as the pellet calibre?
    'cos that'll be too big
    Interestingly the old pre-wat BSA underlevers were made like this, as the loading tap was reamed through. They benefit massively from being sleaved down to 3mm or so - more power, less harsh..

    Another practical reason is to stop your pellets falling back into the cylinder through them
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  15. #45
    Join Date
    Jul 2000
    Location
    Tremar
    Posts
    14,239
    Any void space has to be filled with the air that the piston is compressing, so a port larger than necessary will also reduce the maximum potential pressure.

    A while back I made a number of screw-in ports for a chap who was experimenting with a Walther rifle. The screw-in ports started out as brass grub screws that would screw into a tapped 'port', and they were all primarily drilled 2.0mm. Then with a taper reamer I opened them out, one by one, from 2.1mm in 0.1mm increments up to 3.0mm which was the largest he wanted. I reamed them back to front, if you follow me, so that the hole in the port diverged marginally, as this ought to give a better flow characteristic than a port that got smaller.

    I made the taper reamer from silver steel and the taper was chosen so that I could easily judge the bore size by the depth the reamer had entered.

    I think a taper reamer is a better way to go than a twist drill; it would be remarkable if a twist drill was that accurate, as any imperfection in the grind will make it cut oversize.
    www.shebbearshooters.co.uk. Ask for Rich and try the coffee

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •