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Reloading PSI

Discussion in 'Shooting Related Threads' started by blkfin, Dec 7, 2008.

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  1. blkfin

    blkfin Member

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    I would like to know how to compare LUP to PSI if poosible. Also do the numbers have any relation to recoil. I'm trying to find a load for caps around 1200 FPS that is not at the high end of recoil. I am now shooting 17.9 grains clays,waa12 wad,win 209 primer and AA hulls. Shooting from the 26 it seems like the ( time to break takes forever). Just another head game or would a faster load help? I really do not want to buy more components if it will not help. I hope someone can shed some light on the subject. Thanks Mike K.
     
  2. KEYBEAR

    KEYBEAR Active Member

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    Speed Kills . For most powder to burn pressure needs to be around 9-to 10,000 lb. If I was thinking of shooting a faster shell I would just buy a flat to try first .
     
  3. Recoil Sissy

    Recoil Sissy Well-Known Member

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    blkfin:

    I wouldn't bet serious money on this but I seem to recall reading somewhere that you can add 1000 to an LUP value to get a rough approximation of PSI.

    From time to time ts.commers have raging debates about the relationship if any, between chamber pressure and recoil. I didn't confirm the reference but I believe some of Hodgdon's reloaders guides (it may be Alliant's) says no such relationship exists. No disrespect to those with contradictory views but I'm inclined to accept the opinion of industry professionals who earn their living working with such issues.

    Using the components you listed, Hodgdon calls for 18.2 grains for a 1200 fps load. That said, I would bet the farm neither you or anyone else can tell the difference in recoil or performance between shells loaded with 17.9 grains of Clays versus shells loaded with 18.2 grains.

    If you're determined to reload and see/feel a material difference, you're stuck with trying different components. My first choice would be a slower burning powder like Green Dot or International Clays.

    sissy
     
  4. hmb

    hmb Well-Known Member

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    Green Dot is the best powder for handicap loads. HMB
     
  5. Trap4

    Trap4 Member

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    Hmb--not really there are a lot of very good powders for handicap, there is not one best powder for anything. whatever works for you in your mind or your gun.

    Trap-4
     
  6. halfmile

    halfmile Well-Known Member

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    There is no exact conversion for PSI/LUP. There are approximations but the 2 do not follow the same linearity.

    best not to pursue it or you'll think about it next time you're on the line, and miss.

    HM
     
  7. phirel

    phirel TS Member

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    sissy- I think it was a guy named Sir Fig Newton who first demonstrated that there was not a direct relation between chamber pressure and recoil. He did this work prior to a brain injury caused by an apple falling on his head. The apple did have recoil caused by motion.

    Pat Ireland
     
  8. hmb

    hmb Well-Known Member

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    Sir Fig Newton was wrong. If you have no pressure, you have no recoil, if you have a small amount of pressure, you have a small amount of recoil, and if you have a large amount of pressure, you have a lot of recoil. That sounds like a relationship to me. HMB
     
  9. Trap4

    Trap4 Member

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    Htm--agree with you on the relation of pressure and recoil, sounds like the apple really affected fig newtons brain.

    Trap-4
     
  10. jhoward

    jhoward Member

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    Chamber pressure is not the biggest factor to consider when looking at recoil. I would not go so far as to say that there is no relation, but it is secondary to shot load and velocity. That is, given two 1oz loads both of which will run 1250fps, if one has a chamber pressure of 11,000psi and one has a pressure of 9,000psi, the 9,000 psi load should have less FELT recoil because it has a slower pressure curve.

    Given two different loads, one an 1 1/4oz at 1250 with a chamber pressure of 9,500 and the 11,000 psi 1oz load used above, the 1 1/4 load will have more recoil because of it's larger shot load despite having a lower chamber pressure.
     
  11. timb99

    timb99 Well-Known Member

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    Hmmm, this old argument again.

    I submit that if pressure affects recoil, my .410 loads at 11,500 psi should recoil a lot more than my 12 gauge handicap loads at 10,000 psi.

    But they don't.
     
  12. timb99

    timb99 Well-Known Member

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    "Sir Fig Newton was wrong."

    Now THAT'S funny.

    Actually, it was Sir Fig's smarter brother Isaac.

    If you're comparing a shell with Powder A against a shell with a little more Powder A, all other variables equal, of course you'll get more recoil. But its not because the pressure is higher. Its because the muzzle velocity is higher.

    If you're comparing Powder A against Powder B and all other variables equal (including muzzle velocity and ejecta weight) and one powder has a lower peak pressure than the other, there will not be a difference in recoil.

    Some will submit they can tell a difference in perceived, or "felt recoil" but I'd bet in a double blind, they'd be hard pressed to accurately tell the difference.
     
  13. Recoil Sissy

    Recoil Sissy Well-Known Member

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    blkfin:

    Like I said, we have these periodic debates... This time you stirred it up. Bad on blkfin!

    sissy

    PS: Everybody believes in something. I believe its time for another cup of coffee.
     
  14. phirel

    phirel TS Member

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    timb99- You got it right. How about a test question. How can you get the maximum chamber pressure with no recoil ? (first, think about a barrel obstruction then weld a plug in the barrel)

    hmb- High chamber pressure does not always result in higher velocity.

    Pat Ireland
     
  15. hmb

    hmb Well-Known Member

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    Pat,

    I did not mention velocity and I try to shoot guns that do not have a plug welded in the barrel. Please join us in the real world of recoil. HMB
     
  16. phirel

    phirel TS Member

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    HMB- It is the weight and velocity of the shot/wad/gasses that cause recoil. In general, higher chamber pressures do result in greater velocity and more recoil, but this is not always true. The chamber pressure does not directly produce recoil, only the motion of something forward will cause the gun to move back and bang into our heads.

    Pat Ireland
     
  17. Smity

    Smity Member

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    Gentlemen, I present to you Newton's three laws:

    First law: A particle not subjected to external forces remains at rest or moves with constant speed in a straight line.

    Second law: The acceleration of a particle is directly proportional to the resultant external force acting on the particle and is inversely proportional to the mass of the particle.

    Third law: If two particles interact, the force exerted by the first particle on the second particle (called the action force) is equal in magnitude and opposite in direction to the force exerted by the second particle on the first particle (called the reaction force).

    The shot, in order to move, must have a force applied to it. That force is the chamber pressure. Newton's first law.

    The more force, the faster the shot will accelerate. Newton's second law.

    The force that is applied to the shot (action force) is equal to the force that is applied to your shoulder in the form of recoil (reaction force). Newton's third law.

    F=MA Force equals mass x acceleration. If there is more chamber pressure, then there is more acceleration of the shot -- and more acceleration of the shotgun in the opposite direction.

    The reason that a 410 can have more chamber pressure and less recoil then a larger gauge is because the mass of the shot is less, therefore there is less Force applied in the opposite direction, resulting in felt recoil being less.

    If your shotgun has more mass, it will have less acceleration into your shoulder, therefore, less felt recoil.

    It is not the velocity of the shot that produces recoil, it is the change in velocity over time, also known as acceleration, multiplied by the mass of the shot.

    Bottom line, felt recoil (which is the shotgun accelerating into your shoulder) is directly proportional to chamber pressure, and is directly proportional to the mass of the shot, and is indirectly proportional to the mass of the shotgun.

    Hope this helps.

    Smity
     
  18. phirel

    phirel TS Member

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    Smity- You did well until you got to the last sentence. Chamber pressure is always reported as the peak pressure (pressure spike). It is possible to have a powder with a high pressure spike transfer less total force to the shot. It is not possible to use spike pressures as a measurement of total force applied to the shot.

    Certainly, chamber pressure is the force that accelerates the shot. This acceleration also causes recoil. From that, jumping to chamber pressure as an indicator of recoil may be erroneous. Maximum chamber pressure, the number that is published, occurs well prior to the acceleration of the shot. By the time the shot/wad has opened the crimp, chamber pressure is declining rapidly.

    Pat Ireland
     
  19. Quack Shot

    Quack Shot Active Member

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    Yawn!

    Neil Winston has some neat charts and graphs and this had been hashed out many times before.

    Pressure has little to do with recoil, unless it results in higher or lower velocities. Two loads at identical velocities with the same payload, but with different pressures will have nearly identical or identical recoil energies, given the weight of the gun is constant. Pressure is not a major factor in recoil unless it changes the velocity. I seriously doubt that someone could tell the difference in acceleration, since it's quite a small fraction of a second.

    Merry Christmas!
     
  20. Recoil Sissy

    Recoil Sissy Well-Known Member

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    Dangit blkfin, you got them started again...

    sissy : )
     
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