node help
- Thread starter muzz
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Ridgerunner665
Handloader
- Oct 28, 2008
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I'm glad you asked this muzz...it gives me the chance to tell you something I've been wanting to say for a few days now...and please do not take this as any sort of attack on you because it is not...it is just something that I believe I need to say because I'm pretty sure I'm right and can back it up with some facts if you will allow me to...
That load is way over pressure...likely up near 70,000 psi...regardless of any signs of pressure on the brass or primers.
OK...with that said...my next post will try to illustrate the node concept.
That load is way over pressure...likely up near 70,000 psi...regardless of any signs of pressure on the brass or primers.
OK...with that said...my next post will try to illustrate the node concept.
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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Code:
Cartridge : .280 Ack Imp
Bullet : .284, 150, Nosler Accubond LR 58734 G7
Useable Case Capaci: 65.334 grain H2O = 4.242 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Alliant Reloder-26
Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !
Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms
-20.0 82 53.04 2479 2047 29997 10798 94.3 1.566
-18.0 84 54.37 2548 2163 32231 11128 95.6 1.524
-16.0 86 55.69 2618 2282 34649 11432 96.8 1.482
-14.0 88 57.02 2687 2405 37267 11709 97.7 1.439
-12.0 90 58.34 2756 2531 40108 11955 98.6 1.390
-10.0 92 59.67 2826 2659 43190 12169 99.2 1.342
-08.0 94 61.00 2894 2790 46539 12349 99.7 1.296
-06.0 96 62.32 2963 2923 50183 12492 99.9 1.252
-04.0 98 63.65 3030 3058 54155 12597 100.0 1.209
-02.0 100 64.97 3097 3195 58489 12683 100.0 1.168 ! Near Maximum !
+00.0 102 66.30 3164 3334 63228 12764 100.0 1.128 ! Near Maximum !
+02.0 104 67.63 3229 3474 68411 12840 100.0 1.090 !DANGEROUS LOAD-DO NOT USE!
+04.0 106 68.95 3295 3616 74040 12911 100.0 1.054 !DANGEROUS LOAD-DO NOT USE!
+06.0 109 70.28 3360 3760 80178 12975 100.0 1.018 !DANGEROUS LOAD-DO NOT USE!
+08.0 111 71.60 3425 3907 86888 13034 100.0 0.984 !DANGEROUS LOAD-DO NOT USE!
+10.0 113 72.93 3489 4056 94238 13085 100.0 0.951 !DANGEROUS LOAD-DO NOT USE!
Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 102 66.30 3301 3629 79958 12210 100.0 1.032 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 102 66.30 2950 2898 48741 13201 98.0 1.259OK..if that formatted right (copied and pasted from DrMike's post)...see the "B time" up there? That is the last set of numbers (example 1.556)...That means barrel time...the time it takes the bullet to travel down the barrel in milliseconds (ms)...the "nodes" are the barrel times that coincide with the barrel vibrations being at the chamber end of the barrel while the bullet exits the muzzle...letting the bullet exit at a time when barrel is vibrating the least, or...when the muzzle is moving the least because of vibration and torque.
Here is a list of barrel times by barrel length... http://www.the-long-family.com/OBT%20Table.pdf
The theory explained... http://www.the-long-family.com/OBT_paper.htm
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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Your load is on the fast end of node 4 of a 24" barrel (1.10 ms)...and I don't believe you can get much over 3,120 - 3,150 fps from a 24" barreled 280 Ackley with a 150 grain bullet within normal pressure (65,000 psi) with any current powder...physics won't allow it.
On the QL above...forget the powder charge for this explanation...just look at the velocity, pressure, and barrel time...lets go with 3,229 fps...barrel time is something around 1.09 I think (going from memory as I type this)...the pressure is over 68,000 psi....your load is slightly faster (3,234 fps), that means the pressure is slightly higher (appx. 70,000 psi)
And even getting that 3,120 - 3,150 fps will require running it hard...right on 65,000 psi...brass life will suffer.
Running some Ackley rounds at 68-70,000 psi may not be a huge safety issue...PO Ackley did it for years...his theory was if the bolt stayed in the rifle upon firing then all was well...I'm not so fond of that idea myself though...barrels are expensive, brass is expensive too...and running rounds at increased pressure just shortens the life of both.
If I'm wrong on that load being way over pressure...then I apologize...and will admit to being wrong when somebody proves to me that I am....again, hope I didn't ruffle any feathers...but I felt it needed to be said (others have given subtle hints)
On the QL above...forget the powder charge for this explanation...just look at the velocity, pressure, and barrel time...lets go with 3,229 fps...barrel time is something around 1.09 I think (going from memory as I type this)...the pressure is over 68,000 psi....your load is slightly faster (3,234 fps), that means the pressure is slightly higher (appx. 70,000 psi)
And even getting that 3,120 - 3,150 fps will require running it hard...right on 65,000 psi...brass life will suffer.
Running some Ackley rounds at 68-70,000 psi may not be a huge safety issue...PO Ackley did it for years...his theory was if the bolt stayed in the rifle upon firing then all was well...I'm not so fond of that idea myself though...barrels are expensive, brass is expensive too...and running rounds at increased pressure just shortens the life of both.
If I'm wrong on that load being way over pressure...then I apologize...and will admit to being wrong when somebody proves to me that I am....again, hope I didn't ruffle any feathers...but I felt it needed to be said (others have given subtle hints)
- Thread starter
- #5
No feathers ruffled here. If the others would just say something instead of "hint" that would be better. I mean I am here to learn and be helped if someone sees it fit.
Here is the QL for close to where I am running in my rifle.
-04.0 98 63.65 3030 3058 54155 12597 100.0 1.209
now if I am reading this right the 54155 is the pressure with just a tad bit more powder then I am loading.
So where is the 70,000 plus pressure coming from?
Here is the QL for close to where I am running in my rifle.
-04.0 98 63.65 3030 3058 54155 12597 100.0 1.209
now if I am reading this right the 54155 is the pressure with just a tad bit more powder then I am loading.
So where is the 70,000 plus pressure coming from?
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
- 298
First off...these guys don't wanna be smart asses...they're all very nice and knowledgable folks...don't hold it against them...some folks just don't wanna offend, thats all (I think...not speaking for them, just about them)
OK...Forget the powder charge above...just look at the speed and pressure...the closest to your load is 3,229 fps, use that one.
OK...Forget the powder charge above...just look at the speed and pressure...the closest to your load is 3,229 fps, use that one.
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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If you can measure the actual case capacity of brass fired in your rifle...we can give you an accurate projection that will match...I'll need DrMike's help for that though because I don't have the new QL update yet...or i can give you examples using your case capacity with what appears to be similar powder as far as pressure/velocity goes...that being Norma MRP (see my thread)
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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They key is...and this is ALWAYS true...
Speed isn't free...it takes pressure to produce it.
Speed isn't free...it takes pressure to produce it.
- Thread starter
- #9
DrMike
Ballistician
- Nov 8, 2006
- 37,312
- 5,976
muzz":1tu2czid said:
Let a container of water set overnight (it deoxygenates the water, allowing it to reach homeostatic oxygen tension). Tare a case fired in your rifle (leaving the spent primer in place). With the zeroed case, use a pipette to add deoxygenated water until you form a convex meniscus. The weight of the water is taken as case capacity overfill. This will allow you to generate the required numbers.
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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You'll need a fired case that hasn't been resized or deprimed, a cup of water, a powder scale, and a dropper bottle or syringe without a needle...
Let a cup of water sit out overnight...this is so all the tiny bubbles can make their way out of it...some say that isn't necessary, but I'm thorough, lol.
Weigh the empty unsized and still primed fired case...use the dropper/syringe to fill the case with water....overfill it actually, but not enough that it spills down the sides (wipe off any that does spill down the sides)...just enough that the surface tension of the water makes it rounded on the top, over the case mouth...this is overflow capacity, as is used by QuickLoad...weigh the filled case.
Subtract the empty weight from the filled weight and there you have your overflow case capacity.
The good doctor beat me to it...
Let a cup of water sit out overnight...this is so all the tiny bubbles can make their way out of it...some say that isn't necessary, but I'm thorough, lol.
Weigh the empty unsized and still primed fired case...use the dropper/syringe to fill the case with water....overfill it actually, but not enough that it spills down the sides (wipe off any that does spill down the sides)...just enough that the surface tension of the water makes it rounded on the top, over the case mouth...this is overflow capacity, as is used by QuickLoad...weigh the filled case.
Subtract the empty weight from the filled weight and there you have your overflow case capacity.
The good doctor beat me to it...
- Thread starter
- #12
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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The Ackley won't show pressure signs until you're way over pressure...this has always been said of Ackley rounds, PO himself has always been accused of running some of them at 70,000 psi.
The fact is...the Ackley rounds will give 50-100 fps over standard rounds on the 30-06 case...the 280 Ackley will match most 7mm Rem Mag factory loads which have a lower SAAMI pressure limit (61,000 psi)...if you start beating the Rem mag by any noticeable amount...physics dictate that you're way beyond 65,000 psi.
Elevation has no relevant effect on internal ballistics...
My 280 Ackley won't show any noticeable pressure signs until above 67,000 psi...I fired loads that I know were over pressure while figuring this out and matching QL to my powder....even with a full 70,000 psi, bolt lift was fine, primers looked fine, only a slight ejector mark...the straight walls and sharp shoulders of the Ackley case just don't let brass flow the way we're used to with conventional rounds.
The fact is...the Ackley rounds will give 50-100 fps over standard rounds on the 30-06 case...the 280 Ackley will match most 7mm Rem Mag factory loads which have a lower SAAMI pressure limit (61,000 psi)...if you start beating the Rem mag by any noticeable amount...physics dictate that you're way beyond 65,000 psi.
Elevation has no relevant effect on internal ballistics...
My 280 Ackley won't show any noticeable pressure signs until above 67,000 psi...I fired loads that I know were over pressure while figuring this out and matching QL to my powder....even with a full 70,000 psi, bolt lift was fine, primers looked fine, only a slight ejector mark...the straight walls and sharp shoulders of the Ackley case just don't let brass flow the way we're used to with conventional rounds.
- Thread starter
- #14
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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72.2 grains...
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- #16
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
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It'll be later tonight... I'm on company time right now.
- Thread starter
- #18
- Thread starter
- #19
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
- 298
You could measure a few more cases for a better average if you want.
