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Thread: Let's Blow Up Some Rifles, Boys...

  1. #1

    Let's Blow Up Some Rifles, Boys...

    I love having Saturday coffee with King Peter. We always find something to fight about and this time it was all about gun powder burn rates, pressure spikes and theory - and I think I got spanked. (Not that Pete would ever admit that he's wrong, may God rot his balls!)

    Agree or disagree with the following statements:

    A. You can never blow up a gun with an overly slow burning powder because any unburned powder will be pushed out the barrel and burn out there - and that would dispense with excess powder). For the record I am not sure I agree with that.

    B. Take two cartridges with roughly the same dimensions but different bores (eg. 243 vs 308): You will need a faster burning powder for the 308 than for the 243 because as the 308 travels down the bore, the volume increases and you need a faster burning powder to fill that volume. For the record, I disagree with that. I would think you need a faster burning powder in the smaller bore rifle because you want the combustion cycle to end just as the bullet leaves the barrel - and the smaller volume of the smaller bore would call for a faster burn rate. Of course when we brought up the powder burn rate chart on the cell, the 243 does seem to favour slower powders. That sticks in my craw because typically - don't the big boomer magnums burn smaller powder?

    I think Pete may be right but for the wrong reasons. He finished up his flubdubbery with the statement that optimal powder burn rate is a function of bore diameter. Are any of you boys up to speed on the physics of pressures vs. cartridge vs. powder selection?

  2. #2
    Boolit Buddy gnostic's Avatar
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    Normally, you can't get enough slow burning powder in the case, to blow up the gun.

  3. #3
    Boolit Master
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    A: is assanine and your friend is welcome to earn his Darwin award if he puts this to practice.

    B: well I'm still concerned about A:

  4. #4
    Boolit Master
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    Quote Originally Posted by gnostic View Post
    Normally, you can't get enough slow burning powder in the case, to blow up the gun.
    Load up a rifle case with pistol h110 powder, I'll hold your beer and watch.

  5. #5
    Boolit Master Hick's Avatar
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    What you do is take a relatively large case-- like 30-06. Fill it about 50% with a slow burning powder, then seat the heaviest bullet you have. Then, put it in your rifle horizontally-- so that the powder lies flat all along the length. In this position, the primer fire can reach almost all the powder at the same instant. So-- instead of burning from the primer toward the bullet, it all lights up at the same time. That can blow up your rifle. I can't guarantee it will wreck your rifle, but I wouldn't try it in mine.
    Hick: Iron sights!

  6. #6
    Boolit Buddy Jedman's Avatar
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    Kinda hard to give you a clear answer on either.
    For A - To many variables to say never, but in general what gnostic said is true.

    For B - Again really you have to be comparing apples to apples, If you compare a 243 Win to a 358 Win both the same basic case but you could be shooting a lightweight bullet in the 243 ( 58 gr. ) and a heavyweight bullet in the 358 (250 gr. ) and use the same powder for both and get near the highest velocity at a safe pressure in both. But if your talking 100 gr. bullet in the 243 you will need a slower burn rate powder than the 358 to get maximum velocity at a safe pressure.
    About as clear as mud.

    Jedman

  7. #7
    Boolit Master


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    On B, efficiency is NOT performance. Drag racers will gladly burn twice the fuel for another 0.1 second off their quarter mile. And powder blown out of the barrel may be inefficient, but it may also be the load that produces the best performance within safe pressure limits.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  8. #8
    Boolit Master uscra112's Avatar
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    The ballistic engineering explanation of the S.E.E. phenomenon is this: Load a slow burning, hard-to-light powder into a large case, behind a strongly constructed jacketed or solid bullet. The primer fires, and drives the bullet into the throat, where it stops. It is now a bore obstruction. Millisecond or two later that slow powder finally lights, the bullet doesn't move, and pressure goes thru the roof. BOOM! This was actually observed with an instrumented gun by a lab in Europe while working up a load for a large case 6.5 mm cartridge with a long "cruise missile" style bullet. Put to rest all the old wive's tales about powders detonating and such.

    So yes, it's possible. Not with cast lead, however.
    flectere si nequeo superos, acheronta movebo

  9. #9
    Boolit Master GhostHawk's Avatar
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    As far as I know A is only true for black powder. I would not try it with smokeless.

  10. #10
    Boolit Buddy
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    Don't know about A but in a straight walled case I could see that being so.

    As for B, "overbore" cartridges, meaning large case body to bullet diameter ratio, are more efficient with a slower powder.
    The 243 fits into this category and the ballistics of the cartridge bear this out.
    This is generally true with standard cartridges when using heavy for caliber bullets as well.

    The theory is that the pressure curve is more gradual with a slow powder so the energy expended on the bullet's acceleration happens throughout the travel down the bore.
    This is why pistols use smaller charges of faster powders as the opportunity for acceleration is hampered by the barrel's short length.

  11. #11
    Boolit Master Skipper's Avatar
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    I would think you need a faster burning powder in the smaller bore rifle because you want the combustion cycle to end just as the bullet leaves the barrel
    Just for info, the powder is consumed in about 3.5-4" of the barrel. It's all gas expansion after that.
    Some people try to turn back their "odometers." Not me. I want people to know why I look this way. I've traveled a long way and some of the roads weren't paved.

  12. #12
    Boolit Grand Master

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    Try the slow powders in some semi auto and see what happens, To slow a powder in the garand will bend the op rod as it changes the port pressures. Even the AR15 starts doing strange things with slow powders. While they may not "blow up" the gun, damage is damage

  13. #13
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    Quote Originally Posted by uscra112 View Post
    The ballistic engineering explanation of the S.E.E. phenomenon is this: Load a slow burning, hard-to-light powder into a large case, behind a strongly constructed jacketed or solid bullet. The primer fires, and drives the bullet into the throat, where it stops. It is now a bore obstruction. Millisecond or two later that slow powder finally lights, the bullet doesn't move, and pressure goes thru the roof. BOOM! This was actually observed with an instrumented gun by a lab in Europe while working up a load for a large case 6.5 mm cartridge with a long "cruise missile" style bullet. Put to rest all the old wive's tales about powders detonating and such.

    So yes, it's possible. Not with cast lead, however.
    This is not the definition of SEE, nor is it just possible "Not with cast lead".

    SEE is the transition of burn rate from deflagration to detonation. While it may coincide with the description above, it doesn't have to, it is a chemical property of the energetic material (propellant), usually involving double base propellants containing 1,2,3-trinitroxypropane.

    Think of it this way. Throw genuine dynamite (diatomaceous earth + nitrogyclerine) in a fire, it burns real good. Hit it with a blasting cap, it explodes. That is the difference between deflagration and detonation, and the difference between a good powder burn and SEE. Many think of smokeless powder as exploding because its burn rate seems fast to us humans, but it is an order of magnitude slower propagation rate than detonation. In a gun chamber smokeless powder burns faster than in open air due to higher pressure, but still not fast enough to call it detonation (unless SEE occurs).
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  14. #14
    Boolit Master uscra112's Avatar
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    Quote Originally Posted by HangFireW8 View Post
    This is not the definition of SEE, nor is it just possible "Not with cast lead".

    SEE is the transition of burn rate from deflagration to detonation. While it may coincide with the description above, it doesn't have to, it is a chemical property of the energetic material (propellant), usually involving double base propellants containing 1,2,3-trinitroxypropane.

    Think of it this way. Throw genuine dynamite (diatomaceous earth + nitrogyclerine) in a fire, it burns real good. Hit it with a blasting cap, it explodes. That is the difference between deflagration and detonation, and the difference between a good powder burn and SEE. Many think of smokeless powder as exploding because its burn rate seems fast to us humans, but it is an order of magnitude slower propagation rate than detonation. In a gun chamber smokeless powder burns faster than in open air due to higher pressure, but still not fast enough to call it detonation (unless SEE occurs).

    I "SEE" that science and engineering proofs still haven't penetrated the whole population. Do you also believe in AGW?
    flectere si nequeo superos, acheronta movebo

  15. #15
    Quote Originally Posted by Mica_Hiebert View Post
    Load up a rifle case with pistol h110 powder, I'll hold your beer and watch.
    can i watch too? like 100 or so yards away.....
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  16. #16
    Boolit Buddy gnostic's Avatar
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    Quote Originally Posted by Mica_Hiebert View Post
    Load up a rifle case with pistol h110 powder, I'll hold your beer and watch.
    H110 isn't a slow burning powder for a rifle....
    Last edited by gnostic; 04-08-2018 at 04:16 PM.

  17. #17
    Boolit Master
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    A,, never said never! "In general "kind of rules can lead to BAD things . Documented handguns blown up with reduced loads of 296/h110. If he's talking 4064 In a 375 winchester then I can go along. Never said never, and ect

    B , he's right for the wrong reasons. A larger bore cartridge with the same ish powder capacity will generally, with similar bullet type and sectional density, generate lower peek pressures with the same powder. Again see my thoughts on "A",
    There exist test equipment and pressure tested results too keep the excitement level down.
    True that the larger bore gives a quicker increase in combustion area, and as long as it's a fun conversation over a beer, interesting. Not a good idea to use generalizations to select powders, some powders do NOT follow the rules. H110 being one of those, and NOT a slow rifle powder.
    Last edited by rking22; 04-08-2018 at 05:19 PM.
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  18. #18
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    help: AGW???
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  19. #19
    Boolit Grand Master


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    Quote Originally Posted by uscra112 View Post
    The ballistic engineering explanation of the S.E.E. phenomenon is this: Load a slow burning, hard-to-light powder into a large case, behind a strongly constructed jacketed or solid bullet. The primer fires, and drives the bullet into the throat, where it stops. It is now a bore obstruction. Millisecond or two later that slow powder finally lights, the bullet doesn't move, and pressure goes thru the roof. BOOM! This was actually observed with an instrumented gun by a lab in Europe while working up a load for a large case 6.5 mm cartridge with a long "cruise missile" style bullet. Put to rest all the old wive's tales about powders detonating and such.

    So yes, it's possible. Not with cast lead, however.
    This is the correct definition of S.E.E. There is not "detonation" of the powder. The powder burns faster than the bullet can get moving again with the pressure rising to catastrophic levels. The brass case, the barrel and or the action can no longer retain the pressure and it lets go.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
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  20. #20
    Boolit Master


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    Quote Originally Posted by Larry Gibson View Post
    This is the correct definition of S.E.E. There is not "detonation" of the powder. The powder burns faster than the bullet can get moving again with the pressure rising to catastrophic levels. The brass case, the barrel and or the action can no longer retain the pressure and it lets go.
    The ballisticians I worked with at Ballistics Research Lab, APG disagree with you.

    So does the data I reduced for them.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

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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