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Breach Block Inspection & General Maintenance after 1 Year (>4,000 pellets)

Home Forums BullPups Vulcan Breach Block Inspection & General Maintenance after 1 Year (>4,000 pellets)

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    Recently tore down the breach block for preventative maintenance and inspection after over 4,000 pellets over the last year.

    This is on a generation two 22 gauge with free floating hammer configuration. The hammer and spring configuration may differ if yours is a different generation or caliber. My spring does NOT travel all the way forward during firing. It stops against the breach block and the hammer flies forward free of the spring. Mine also has a DIY hammer spring damper and Delrin spring guide. I believe the 25 gauge and 22 gauge from generation 3 onward, omit the spring guide completely. Instead, the rear of the hammer has a short circular hub onto which the spring engages. The spring travels with the hammer all the way to the valve pin on later generation guns. The design change reduced the incidence of things hanging up and varying strike force.

    Since writing this, I have changed to the newer generation style hammer and spring. The newer hammer and spring configuration is quieter because no spring guide slaps against the breach block.

    The newer hammer and spring configuration are also needed to use a degassing tool provide for Vulcans that do not have a degassing valve on their firing valve assemblies. The spring guide configuration would interfere with the degassing tool.

    Inspection today was largely pleasing.

    There were a couple wear points and loosening bolts after a year of use. All were easily addressed. Some wear areas may be worth addressing early to reduce ongoing wear. I had already switched nearly the entire breach block to Dri-slide way back at the beginning when I noticed that the factory oil was not preventing wear of the brass elements, especially the pellet probe.

    To enable inspection and cleaning, I completely removed the hammer and pellet probes. That let me inspect them and the barrels in which they ride. The barrels surfaces were cleaned then re-lubricated with a thin coat of Dri-slide. (moly dry lube)

    Hammer, pellet probe, spring, spring guide were all cleaned, polished if needed and lubricated lightly wth dry slide. All parts were allowed to dry completely before reassembly.

    1. When the gun was new, it had a factory brass spring guide. That was spalling as it impacted with the breach block with each shot. Replaced that brass guide with a Delrin guide nearly a year ago. No further wear material has accumulated in the hammer spring chamber.

    2. Pellet probe body was factory lubricated with oil. The entire barrel housing of the pellet probe had been awash with lots of brass swarf. None was seen at this time despite thousands of cocking actions. The key was switching to Dri-slide instead of oil. Removing and inspecting the entire pellet probe revealed some minor wear, but nothing severe. There were no visible brass rubbings inside the guide barrel.

    3. Clip holding the cocking plate and part of the trigger mechanism had loosened out about 0.5 mm. The clip is easily pressed back into position provided you provide counter pressure on opposite end of pin.

    4. Bolts for cocking extensions of hammer and pellet probe were slightly loose.

    5. There was significant notching of the pellet probe cocking extension. That part suffers high pressure wear and slides against the cocking plate. Examination of the cocking plate mating surface revealed surpassing roughness where it engages the round cocking extension. Some was nearly as rough as a file. I wish I had checked that when the gun was new. On the other hand, it was amazing that 4,000 cocking cycles had not cut further into the pellet probe’s cocking extension.

    To reduce future wear, I completely removed the cocking plate. Took just a few minutes to smooth & polished its engagement edge surfaces to near mirror finish with a fine Dremel sanding drum and pollishing wheels. I also polished the worn portions of the round cocking extension. During reassembly, the cocking extension was rotated to present a fresh surface to the cocking plate. Just smooth the surfaces, don’t remove too much metal.

    I think it worthwhile to check the smoothness of a new gun’s cocking plate engagement surfaces and smooth them before they can wear into the cocking extensions.

    6. Hammer had very minor scratching. Engagement point of hammer with sear was minimally marked. After repolishing with flitz, the hammer was smooth, shiny and the minor marking at the sear engagement was gone. Basically, the sear isn’t wearing out its contact point on the hammer.
    Don’t be confused by my hammer’s silver appearance. The hammer was originally black. I polished it to full shiny silver when gun was new.

    7. Since the cocking rod was already out, I polished it to mirror smoothness.

    8. Cocking rod is connected to pellet probe via two bolts. Those were slightly loose. It is best to have the probe advanced forward into the barrel when tightening its two bolts. Otherwise, alignment may be slightly off. I would advance the pellet probe with both bolts loose and then successively tighten each much like tightening scope ring bolts.

    9. New foam dampers made from earplugs were installed for the hammer spring and cocking return spring. The old ones were actually still in good shape.

    Overall, I am very pleased with how little wear has occurred. None of nasty, brass wear happening early in the guns’s life (when the pellet probe was factory oil lubricated) has recurred. The only point of major wear was due to roughness of the cocking plate’s edge (especially near its hooked end). That is easily fixed and worth checking even on a new gun.

    The only unexpected change over time was slight loosing of the pin clips. When those are loose, the cocking lever has more lateral wobble. There is a thin washer between the cocking plate and breach block. When the pin clip is pressed in properly, the cocking lever remains largely out of contact with the breach block surface.

    Dri-slide has done an incredible job for reducing wear of the brass pellet probe. No amount of lube could have prevented the rough edge surfaces of the cocking plate from causing wear. Mine had portions nearly as rough as a file. I’m pretty sure, things will wear more slowly now that the mating surfaces are smooth.

    I used a tiny amount of moly grease along the high pressure contact edges of the cocking plate. Everything else is just Dri-slide lubricated.

    BTW, the slight silvery appearance near the bolt holes is some residual anti-seize


    Nice write up Guykuo. I think I’ll do the same to mine today.


    Guykuo, This is awesome, thank you for sharing! :4: :4:


    What do you suggest for a maintenance schedule (overall)? I’ve only had my Gen4 for a few months, but have already ran around 1200 pellets through it.


    I don’t have a fixed schedule for the Vulcan. It holds up remarkably well over a lot of shots. You don’t want to overdo maintenance and cause more problems than you prevent. Mostly I just listen and feel for any changes in the mechanism.

    Roughly, I have been doing…

    500 pellets – (sooner if pellet probe advance feels harder).
    Re-lube barrel o-ring with silicone grease. Check cocking lever bolts

    1000 pellets –
    Lube fill probe o-rings with silicon grease. Just the barest amount!
    Tighten cocking bolt (if not using lever kit)

    2000 pellets –
    Clean barrel.
    Replace barrel o-ring if gun fails “tissue paper” test over breach.
    Check cocking rod bolts in upper breach block for tightness. Upper breach is accessed without need to pull action out of stock.
    Repeat shot string to test for increased variability in FPS. Shot string also useful to verify continued proper function of regulator.
    If FPS is stable, no need to pull the action. If you note unusual changes in the shot string, pull the action to access hammer and spring. Check hammer is moving freely. Clean the hammer, spring, spring guide and hammer barrel. Re-lube with dry-slide if needed. Don’t forget to clean and lube the INSIDE of the spring guide (If gun has a spring guide)
    Lube amidships barrel & cocking rod slider with moly paste.
    Check 2 stock bolts

    4000 pellets –
    Pull action out of stock for this service.
    Check pin clips of cocking plate are tight.
    Clean hammer and pellet probe barrels. Lubricate mounting barrels with dri-slide.
    Check body of hammer is free of nicks, especially at hammer/trigger mechanism engagement point at front of hammer body.
    Re-polish hammer and pellet probe body if needed.
    Check cocking plate edges and round cocking extensions for wear. Polish as needed. Lubricate high pressure sliding areas of cocking mechanism with moly paste.
    Check that hammer spring has not taken a permanent bend.
    Bump test breach to verify trigger is still stable.
    Readjust trigger if needed to not fire when breach is impacted with mallet.
    Check safety is smooth and functioning. Readjust and re-lube safety slide. Polish safety slide if gritty.
    Check 8 bolts at bottom of trigger blade assembly
    Check 2 bolts holding picatinny rail

    8000 pellets –
    Tighten Allen bolt at shroud midpoint if shroud has any palpable play.
    Remove and clean shroud baffles. Replace o-rings in shroud if no longer pliable.

    4 years –
    Full tear down and replace o-rings throughout. Service air regulator internals.

    Don’t take this as gospel. It’s just what I’m doing or planning to do. The Vulcan doesn’t have a lot of things that wear out quickly. It is mostly just keeping things tightened, lubricated, and clean. The only big wear item I have found was the rough edges of the cocking plate. Address that early and you’ll save quite a bit of wear on the pellet probe’s cocking extension.


    This should be a sticky.

    quote :

    Re-lube barrel o-ring with silicone grease

    Are you talking about an o-ring within the ID of the barrel at the breach end? I’m looking at the schematics, but can’t tell if there is one present. If so, what’s the best method for doing this? Q-tip (de-fuzzed) with silicone on it?


    Yes, it is inside the barrel’s breach end, about 3 mm inset. That is what seals the probe with the barrel when you advance the bolt. That o-ring has both the pellet and pellet probe slide past it every cycle. Just a little silicone lube on a q-tip will keep it sealing properly and forward cocking action smoother. Bend the end of the q-tip 90 degrees to make application easier.

    I use Trident “Pure Silicone Grease.” The 2 oz jar will last a very long time since you use such a tiny amount at time.

    BTW, if you feel any notchiness during the rearward portion of the cocking cycle, check the cocking rod bolts ASAP. If those bolts are loose, the pellet probe cants and rubs against its housing barrel.


    Fantastic! Thanks for the information. For giggles (and to support my addiction to diving) I work part-time at a dive shop. So, I’ve pretty much got a lifetime supply of Trident.

    I was thinking about using PFPE (Perfluoropolyether) combined with PTFE (polytetrafluoroethylene) instead of Trident. It’s what I use when rebuilding regulators. We use it because it doesn’t react with oxygen, solvents, or just about anything, and obviously o-ring safe. It’s an excellent lubricant, but it costs an arm, a leg, and both of your kidneys. The brand is called “Christo-Lube”.


    While we are at it….

    The Picatinny rail’s bolt holes are pretty large compared to the diameter of the two mounting bolts. Despite the beveled bolt heads, the left/right angle of the rail can vary during mounting due to the hole tolerance. 5 mil brass shim is just the right thickness to occupy the slack. Cut a piece long enough to fill entire length of bolt hole. Curl brass into cylinder shape & press into the bolt holes. Mounting bolt will stay centered and no longer wiggle.


    EDIT: Copied from another thread to make this mod information more readily accessible..

    I was asked to outline how to eliminate all the ping noises including (the firing valve ringing)

    Here they are in order of importance.

    1. Firing Valve Spring and Retaining Disc
    This is a medium pitched “twoong” that last about 1/4 second after firing. It is as loud as the main spring twang, but from within the rear of the air cylinder and thus difficult to locate its source until now.

    Strking the firing valve makes the spring and its retaining disc ring with surprising loudness. This is easily demonstrated when the valve assembly is off the air cylinder. Just rap the firing valve pin with your fingernail and you will hear the spring and the spacer ring loudly.

    Damp this with a simple, arrow shaped, damper pushed into the center hold of the retaining disc.
    Once, more that old silicone iPod cover was used as the raw material. Cut to a shape as shown in this image. The shape holds it in place.

    2. Hammer Spring Damper
    This is the relatively low pitched “Pong” noise of the hammer spring. Of the three ping noises, sources this is the 2nd loudest. Newer Vulcans have a silastic tube on the spring to tame this noise. Here on the forum, a rubber grommet is often used. Personally, I use a foam earplug that has had a hole punched through it as my damper. It works very well.

    To install, you must remove the hammer and hammer spring completely. Feed the hammer and spring through foam to install. Be sure to position the foam so it does not come into contact with the small cocking return spring.

    While you are in that portion of the gun, you can also damp the vibrations of the small cocking return spring by pulling a bit of foam into the center of that spring. Look carefully inside that spring in this image and you can just make out the gray foam.

    3. Regulator Air Chamber Spacer
    This is the aluminum tube that creates the regulated air chamber between the firing valve assembly and regulator. Ringing from this is higher pitched “ting.” It is not as loud as the hammer spring “pong,” but very noticeable.

    The classic approach is to lathe grooves for o-rings near each end of the spacer. O-rings then damp the spacer’s ringing. I don’t have a lathe, but instead put 1.5 layers of electrical tape around the spacer. The tape will need to be slit to make it narrow enough. Two layers will be too thick.

    EDIT: Omit the silastic washer in my picture. It ends up entirely inside of the spacer tubing due to the high compression force between the spacer and regulator. It isn’t needed with the 1.5 layers of electrical tape in place.

    What doesn’t work…..
    “Air Tube De-Pinger”
    Your read about these on the internet. People stuff rolled up tubing, fancy baffles, or a bottle brush into their air cylinder to break up the traveling wave. That does nothing on a Vulcan. The shock wave from the firing valve is blocked by the regulator. No noise producing wave bounced back at for in the air cylinder. I tried a bottle brush. Had zero effect. Don’t add such a “de-pinger” to a Vulcan. It just reduces your air cylinder usable volume.

    Now that I have all three major ping noises tamed (and my bottle brush “de-pinger” removed), my Vulcan is finally free of the pinging that annoys with each shot.


    I just wanted to tell you how much I appreciate your knowledge, and your willingness to share it.



    I try to give back to the forum. I was a newbie a very short time ago, but the Vulcan has been a pleasure to use and work on. Evgeny’s amazing customer service and easy to understand design combined with highly accurate repeatability make the Vulcan a winner.

    Here is mine after changing to the current configuration hammer and spring. Omission of the spring guide also makes the firing noise quieter. No slap of the guide against the breach body, just the hammer hitting the valve pin.



    Sticky Sticky Sticky!!!

    Vulcan is here to stay and this info is hard to come by just from searching.



    greetings, please can you re upload these pictures. can’t see the images may be its just me. thanks


    We can thank Photobucket for making a lot of images go poof.
    PITB in the but editing the old posts to point at new uploads.

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