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Thread: Seating off the lands

  1. #16
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    quickload has a generic 7200 psi add for seating at the lands vs off.

    Quote Originally Posted by Lou Murdica View Post
    great reply KEN
    just to add the difference between in the lands and out, adds about 4000 to 6000 PSI to your load and changes the spike in the ramp up
    in the case.

  2. #17
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    Quote Originally Posted by K Hope View Post
    Lacking on both counts but do have a few theory's:

    Pressure and bullet motion in relation to time and location:

    Itís the primer output that drives a stress wave / powder compression through the powder to the bullet. A shower of hot particles and gases start the bullet into the engraving process largely by a passive medium push. With no ullage the powder acts similar to an imcompressible fluid transmitting the primer force to the bullet with no significant chamber pressure mid case forward. This initial bullet movement reduces the amount of brass / bullet surface contact and the amount of tension or grip.

    After the primer push at some point between engravement, and obturation, gas pressure is in short supply with somewhat of a pressure plateau or static load; bullet movement lacking. Shortly, significant gases and pressure build in the case from the rear to the base of the bullet and then the same at the neck. Pressure builds from the rear expanding the neck as it moves forward until obturation.

    The brass not only has to withstand high internal pressures but, it also undergoes deformations in order to seal the chamber; case material properties e.g. strength and ductility consistency maintain the required level of tension.

    Initial bullet movement and Initial Burn Rate have to match every time. Any pressure changes through case volume uniformity (e.g. compressibility % and Temperature) or neck tension (e.g. sizing, maintaining and detaching) and when blow by starts (seating depth) make a big difference as to the peak pressure value. (time and position)

    Burn Rates are about how long pressure stays high along with velocity but, Initial Burn Rates and Initial Bullet Motion (Impulsive Force) are more about where the bullet is located in relation to peak.

    Not mentioning vibration..........

    BR

    Ken
    Wonder if the Pressure Trace II system would provide detailed enough traces to show the difference between seating depths. How would you describe what happens if the bullet is seated with a hard jam?
    Last edited by adamsgt; 08-23-2019 at 10:32 PM.

  3. #18
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    Quote Originally Posted by adamsgt View Post
    How would you describe what happens if the bullet is seated with a hard jam?
    I do not believe there is any one, fit all answer to your question and is dependent on the specific cartridge. Eg Compressed loads versus ullage, bullet design and distance of travel to obturation.

    I defer to others more qualified to answer your question than I am.

    I shot a bit with a couple of brothers from VT. Two top notch shooters; one was a strong believer in hard jam and spent a lot of time with his dies and in setting his loaded rounds straight. The other brother was a strong believer that more powder was the answer when he lost his tune. I tried both these methods but never had much luck. That being said these guys had years of experience and were using select bullets and blended powders. It certainly worked for them but for me it was like living on the edge.

    BR

    Ken

  4. #19
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    ullage
    why do you insist on using this tern in the metallic cartridge world ?

    meaning: the space in a closed container of liquid that is not filled by the liquid:
    from the liguid world, as in cask filling.

    we have always used % full

  5. #20
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    Quote Originally Posted by retired View Post
    ullage
    why do you insist on using this tern in the metallic cartridge world ?

    meaning: the space in a closed container of liquid that is not filled by the liquid:
    from the liguid world, as in cask filling.

    we have always used % full
    Ullage is a common term used in IB best describing free volume; it facilitates visualizing powder orientation within case that can produce changes in pressure and velocity.
    Check it out on Google; here is an example:

    https://ndiastorage.blob.core.usgovc...Lusto19293.pdf

    BR

    Ken

  6. #21
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    please try again.
    the term was so uncommon/unknown it had to be defined at the very start of the article.
    that does not sound like "common" to me.

    Quote Originally Posted by K Hope View Post
    Ullage is a common term used in IB best describing free volume; it facilitates visualizing powder orientation within case that can produce changes in pressure and velocity.
    Check it out on Google; here is an example:

    https://ndiastorage.blob.core.usgovc...Lusto19293.pdf

    BR

    Ken

  7. #22
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    Quote Originally Posted by K Hope View Post
    I do not believe there is any one, fit all answer to your question and is dependent on the specific cartridge. Eg Compressed loads versus ullage, bullet design and distance of travel to obturation.

    I defer to others more qualified to answer your question than I am.

    I shot a bit with a couple of brothers from VT. Two top notch shooters; one was a strong believer in hard jam and spent a lot of time with his dies and in setting his loaded rounds straight. The other brother was a strong believer that more powder was the answer when he lost his tune. I tried both these methods but never had much luck. That being said these guys had years of experience and were using select bullets and blended powders. It certainly worked for them but for me it was like living on the edge.

    BR

    Ken
    LOL!!

    Both "strong believer" and "years of experience between them" could qualify as the understatement of the year

    And may I add that the elder brother..... the one who liked to tip the bottle to regain his groove, was #2 in Group BR HOF for a loooong time..... and simultaneously in the Top 10 for Score.....

  8. #23
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    BTW I'ma get with retired on this one...... thems some perty fancy verbiages to say "the bullet starts and stops some, and we want it to do it the same each time"..... and I LIKE verbosity!



    LOL

  9. #24
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    Quote Originally Posted by alinwa View Post
    BTW I'ma get with retired on this one...... thems some perty fancy verbiages to say "the bullet starts and stops some, and we want it to do it the same each time"..... and I LIKE verbosity!



    LOL
    I am still recovering from jet lag and a 12 hour time change.......... I will try and do better next time.......

    BR

    Ken

  10. #25
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    Quote Originally Posted by K Hope View Post
    I am still recovering from jet lag and a 12 hour time change.......... I will try and do better next time.......

    BR

    Ken



    LOL


    please, allow me to comment without taking it as preaching you have the right to your way, I have the right to mine. It'd be pretty boring if we were all the same!

    That said, I'm a wordy guy and I still thought it was a liddle high falutin'........it's nice when everyone in the room can understand what's being said.


    I was in a pre-con meeting a couple days ago, Concrete, Excavation and Electrical Contractor, and this electrical engineer leads with "OK, since you deem this project time sensitive let me broach the salient subject, are you vendor agnostic? Open sourcing will significantly alleviate funneling and . . . . ."

    At this point the GC raised his hand and asked "If you mean "can we buy or supply our stuff as we see best" then YES! That's what we hired you for....next question?"

  11. #26
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    Quote Originally Posted by K Hope View Post
    Not mentioning vibration..........Ken
    Excellent hypothesis, Ken. Thanks for taking the time to post.

    Good shootin' -Al

  12. #27
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    Depends on one's

    Quote Originally Posted by retired View Post
    please try again.
    the term was so uncommon/unknown it had to be defined at the very start of the article.
    that does not sound like "common" to me.
    education level I'd guess. I've always loved language and words that exactly describe what one wishes to say so I have done my best to learn every word and it's meaning someone was kind enough to offer me.

    Pete

  13. #28
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    BTW, how many of you believe the powder "acts as an incompressible fluid?"

    It takes around 600 actual pounds to start the bullet, ie if you push it with a stick it takes a 600lb weight on the stick for it to engrave the bullet.

    If you push on the POWDER with a stick, does 600lb get transmitted forward? or does the powder compress/crumble some?

    IMO the powder simply decreases the gas space and the primer pressure goes thru it as though it were porous.

  14. #29
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    I lost my head; I almost responded to A.

  15. #30
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    i agree,
    but look at the meaning:

    meaning: the space in a closed container of liquid that is not filled by the :
    from the liquid world, as in cask filling.

    LIQUID

    it is being MIS-USED....

    Quote Originally Posted by Pete Wass View Post
    education level I'd guess. I've always loved language and words that exactly describe what one wishes to say so I have done my best to learn every word and it's meaning someone was kind enough to offer me.

    Pete

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