ADvertise hereTitan ReloadingStainLess Steel MediaInline Fabrication
Graf & SonsRotoMetals2Lee Precision

Results 1 to 12 of 12

Thread: temperature sensitivity

  1. #1
    Boolit Master
    Join Date
    May 2017
    Posts
    713

    temperature sensitivity

    Since I have seen youtube videos promoting the "fine art" of dieseling an airgun as a good safe way to increase performance, I am curious as to how much temperature an airgun pellet can take before it simply liquefies in the barrel.

  2. #2
    Boolit Master

    Join Date
    Feb 2008
    Location
    Bozoland Mt.
    Posts
    1,305
    A proper answer to you question requires a number, sorry I don't have one.

    But getting lead hot enough to melt also takes time, and barrel time is pretty short.

    Accuracy should fall off due to the skirt getting hot and soft before the pellet liquefies.
    To lazy to chase arrows.
    Clodhopper

  3. #3
    Boolit Master

    Join Date
    Mar 2013
    Location
    Northwest Ohio
    Posts
    7,518
    Theres also the fine line between swelling the skirt to seal and blowing it out and loosing accuracy. Dieseling may increase velocity but also may deform the skirt causing accuracy issues. A pellets skirt is a pretty delicate thing in reality. Some form their skirts over a mandel to make a better seal and load with the same tool. It does make a small difference in the target grade guns sometimes. I would also suspect "dieseling" on an air gun could be hard on it.

  4. #4
    Boolit Master rsterne's Avatar
    Join Date
    May 2013
    Location
    Coalmont, BC
    Posts
    200
    Dieseling is VERY hard on the airgun, and if taken to the extreme can break the spring.... Damage to the piston seal is also typical.... There is also virtually no consistency in the velocity using such a practice intentionally.... I don't think you could generate enough heat for a sufficiently long period of time to melt the pellet, however....

    Bob

  5. #5
    Boolit Master
    Join Date
    Dec 2009
    Posts
    4,396
    I wonder if a non flammable gas injected into the cylinder would be heated enough by compression to expand rapidly increasing velocity over that of simple atmospheric air.

    A commercial spring piston diesel gun used ether supplied in glass capsules from veterinary supply stores.
    After WW2 some German gunsmiths altered airguns to diesel using wood alcohol injected into the cylinder by a perfume bottle sprayer.

  6. #6
    Boolit Master rsterne's Avatar
    Join Date
    May 2013
    Location
    Coalmont, BC
    Posts
    200
    Any non-flammable gas should act just like air.... compress it suddenly it gets hot and raises the pressure further (Adiabatic compression).... If you used a liquid (some have suggested water being flashed to steam) the energy required to "boil" it removes energy from the system....

    BSF built a Springer just after WW2 that used a measured volume of Ether injected into the compression chamber to boost the velocity through combustion.... few of them remain....

    Bob

  7. #7
    Boolit Master
    Join Date
    Apr 2010
    Posts
    794
    there is no gain to dieseling your air rifle..... sort of like un regulated nitrous oxide getting dumped into your engine at various times. Unless you can control the action you only gain some peak cylinder pressure.
    Lead needs to be 621'F to melt. just to add diesel'n your pellet guns the pellet is that last of your worries for the added heat and stress.

  8. #8
    Boolit Master
    Join Date
    Apr 2009
    Location
    What the world calls "Global Warming", we in Arizona call "Summer Time."
    Posts
    1,562
    I think that in the long run it's cheaper to just by a 22 rim fire than to go through the process of eventual or inevitably damaging to your air gun but on the other hand, if someone found a safe repeatable recipe for dieseling an air gun it might make it worth while. There are so many variables that can effect the outcome of each shot that I doubt such a recipe could be found.

    HollowPoint

  9. #9
    Boolit Master
    Join Date
    Dec 2009
    Posts
    4,396
    I'm sure there are modern synthetic materials that could be used for piston cups and seals that would withstand any possible abuse of dieseling.

    A battery powered pre heater for both combustion chamber and fuel reservoir would improve consistency of shot to shot velocity.

    A liquid fueled diesel airgun would be immune to restrictions on ammunition and market driven shortages like the recent .22 RF droughts.

    Hobbyist could then spend a lot of their spare time working up custom fuel blends and adjusting charges just as they now do in firearms reloading.

    I'm wondering if the model airplane fuels have been tried in this application. Even if a battery driven glow plug were needed for reliable ignition.

    I suspect that the larger the bore of cylinder as well as barrel the more consistent the velocities would be.

  10. #10
    Boolit Master
    Join Date
    Apr 2009
    Location
    What the world calls "Global Warming", we in Arizona call "Summer Time."
    Posts
    1,562
    In my mind I picture a small dab of liquid propellant that quickly solidifies after being applied and stays in place inside the skirt on the flat at the base of the pellet. Like maybe a pinhead sized dab of the smallest sized gun powder granules mixed with some type of adhesive that would give one enough time to apply the mix before it dried in place.

    It would have to be something that could be repeatedly applied in the same amount every time for consistency; and something that would be ignited with the pressure produced by the air gun being used.

    HollowPoint

  11. #11
    Boolit Master

    Join Date
    Feb 2008
    Location
    Bozoland Mt.
    Posts
    1,305
    Expanding on Multigunner's comments and ideas, what if the compression chamber was .500, and the piston was the back half of an AR-15 bolt?
    Had a small spark plug mounted in the firing pin hole. Then a linear magneto that stroked as the piston rushed forward.
    The thing should run on 50:1 two stroke fuel.
    wear safety glasses
    To lazy to chase arrows.
    Clodhopper

  12. #12
    Boolit Master
    Join Date
    Dec 2009
    Posts
    4,396
    Quote Originally Posted by HollowPoint View Post
    In my mind I picture a small dab of liquid propellant that quickly solidifies after being applied and stays in place inside the skirt on the flat at the base of the pellet. Like maybe a pinhead sized dab of the smallest sized gun powder granules mixed with some type of adhesive that would give one enough time to apply the mix before it dried in place.

    It would have to be something that could be repeatedly applied in the same amount every time for consistency; and something that would be ignited with the pressure produced by the air gun being used.

    HollowPoint
    This would be much like the homemade rocket ball projectiles some have experimented with for the old daisy diesel firing rifles. They stopped manufacturing the rocket ball pellets just as I had decided to buy one that had been on the shelf at a auto parts/hardware shop and was marked down.

    If I'd known that these would also fire regular .22 pellets at over 300 FPS I'd have gone ahead and bought it any way.

    The daisy used lead slugs with a solid propellant bonded to the base.
    The home made version uses a common gun powder formed by first dissolving in a solvent then allowed to set after filling the pellet base.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check