ScopesAndAmmo.com Store Logo

+ Reply to Thread
Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: QB78 Hammer Mods

Hybrid View

  1. #1
    Senior Member remtom1200's Avatar
    Join Date
    Tue Jan 3 2012
    Posts
    323

    QB78 Hammer Mods

    There is something missing....a mod I feel has to be done to my QB78 pcp converted spike driver. The hammer bounce has annoyed me since I turned up the heat on this rig, and hearing wasted air exit the barrel after the pellet has left is saddening. My AT44 has such a nice crisp snap to it which is hard for me to figure out what I could do different to the QB as I dont remember any debounce system in that setup on that hatsan. Now I call it the hammer stop, which is the steel dough-nut the hammer slams into after driving the valve pin foward, The AT44 has a brass dough-nut? This is just an idea with no evidence of it making a difference on the QB but if you tap two steel ball peen hammers together face to face they bounce with little effort or force. Tap a pall peen hammer and a brass hammer together?.... you get bored and go mix another drink . Does machining a brass hammer stop sound like an experiment to try in the QB to anyone or has this already been done?
    For every mile of road, there's two miles of ditch

  2. #2
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    I think you will find that unless you REALLY have the hammer spring tension dialed up, the hammer in a QB isn't hitting the valve retaining collar (that you are calling a hammer stop).... The hammer bounce is a combination of the balance of the two springs and the air pressure, and the hammer weight.... Have you tried dialing back the hammer spring preload while shooting through a Chrony?.... It is quite possible you have too much hammer strike, and reducing it may well increase your shot count, reduce the hammer bounce, while not losing any velocity at all.... This is assuming you are running a regulated setup.... What pressure are you running?....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  3. #3
    Senior Member remtom1200's Avatar
    Join Date
    Tue Jan 3 2012
    Posts
    323
    I agree, have to add a chrony to the list of tools I need(want).
    For every mile of road, there's two miles of ditch

  4. #4
    Senior Member remtom1200's Avatar
    Join Date
    Tue Jan 3 2012
    Posts
    323
    I am running an unregulated setup, with valve mods and a velocity adjuster. Im using 1200psi to propel 23 full power shots with jsb exact 18gr(3000-1800psi) which is good for me. The bounce wasnt an issue until I started shooting the AT44 which revealed the QB's waste air out the muzzle. My curiousity is what makes the AT44 not bounce. I havnt changed out the transfer port for a smaller one yet on the QB.
    For every mile of road, there's two miles of ditch

  5. #5
    Oh Bob Please
    Barrel harmonics? Is there not enough to think about with just the parts and pieces I can see? Is there something more than cosmetics, and a place to mount the site post, on the Crosman 2300 "muzzle break?" Please tell me that the harmonica (Sp intentional) issue only gets heard from at high pressures beyond my co2 levels!!!!!

  6. #6
    Senior Member SeanMP's Avatar
    Join Date
    Thu Dec 22 2011
    Location
    Just south of "Out There"
    Posts
    911
    Sadly the Harmonica can be heard even on my 500fps match rifle. Tuning harmonics is for me one of the most interesting aspects of airguns...rifles in general actually
    Sean

  7. #7
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    You're doing something wayyyyyyyyy different than I have ever done with a QB.... I've never used over 2000 psi.... so you must be using quite a bit stronger hammer spring to allow those pressures.... You say "full power" shots.... what is the velocity string looking like?.... What is the volume of your air tube?....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  8. #8
    Senior Member remtom1200's Avatar
    Join Date
    Tue Jan 3 2012
    Posts
    323
    I have the 3000psi pcp conversion tube from Eric, I do not have a chrono at my disposal so I spend alot more time with poa and poi with a given number of shots to determine "full power" to drop off, as well as using chairgun. This has enabled me to tune for accuracy the long way around but has proved to be a good method with the tools I had. There is a correction to my type of pellet.....premier hollow points 14.3gr in the QB, the jsb's are what I use in the AT44. Bob, have you converted a QB with one of the kits Eric sells? I kinda keep an eye out for your tunings as I've learned alot.
    For every mile of road, there's two miles of ditch

  9. #9
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    YA, I tune to the "Q" above middle "Z"....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  10. #10
    Moderator rsterne's Avatar
    Join Date
    Wed Dec 7 2011
    Location
    Coalmont, BC
    Posts
    1,266
    Nope, I've never used a CrMoly tube on a QB.... I use a 13CI tank regulated to 1600 psi.... My current .22 cal does 40 shots at 35 FPE (928 fps with JSB 18.1 gr).... but if I dial it down to 900 fps I get 60 shots....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

+ Reply to Thread

Similar Threads

  1. Hatsan .25 cal AT44S-10 Long Mods
    By rsterne in forum Co2 and Pre-Charged Pneumatic (PCP) guns.
    Replies: 39
    Last Post: Aug 27 2018, 01:07 PM
  2. New to Forums, Airguns and Crosman Mods
    By Poor-man Plinker in forum Introduce Yourself
    Replies: 4
    Last Post: Aug 08 2012, 09:42 AM
  3. Hammer's M4-177 (finally!!!!)
    By Hammer Sandwich in forum Airgun Picture Gallery
    Replies: 8
    Last Post: Jul 14 2012, 03:51 PM
  4. I'm Hammer Sandwich....and I am stupid
    By Hammer Sandwich in forum Tavern Talk
    Replies: 8
    Last Post: Apr 06 2012, 12:17 PM
  5. Regulated HPA and Hammer Strike
    By rsterne in forum Co2 and Pre-Charged Pneumatic (PCP) guns.
    Replies: 3
    Last Post: Mar 24 2012, 07:56 PM

Posting Permissions

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