node help

[Ridgerunner665]

ES and SD that low has nothing to do with nodes...

There is a point where it becomes important to understand exactly what is required of a load... For 1,200 yards and beyond.... Starting to get into the difference between accuracy and precision.

If a slightly slower load still has the low ES and SD and is more accurate... Then go with the load that is on the node... But if ES and SD suffer stay where you're at... The ES and SD is very important for an extreme long range load, sometimes more important than accuracy...

Nodes make small groups.... But other factors come into play at long ranges.... Things that don't really matter at 600 yards are very important at 1,200 (you already know this)

Someone here posted a load for their 280 Ackley the other day... Nice small group about .5 MOA... But the SD was something like 25 fps I think.... A perfectly good load for anything less than about 800 yards, but beyond that the varying velocity causes the trajectory to fluctuate too much for hunting use... Enough to cause misses on pie plate sized targets.

Its not all about the nodes....

 

[Ridgerunner665]

Cole,
I just realized I ran that other QL without changing the case capacity..its not accurate...sorry about that, hadn't been awake long enough yet.

This one is accurate and gives a good show of why your load is working so well for you...it is on the node at 1.224 ms and with an ES and SD that low it can't miss unless you make it :wink: ...

Ba adjusted only slightly...from .5130 to .5190...H4350 is one of the very few powders that is generally pretty accurate within QL...thats how I caught my mistake, didn't seem right to adjust H4350 that much....your load isn't hot at all...perfect in very way IMO.

Cartridge          : .260 Rem
Bullet             : .264, 139, Lapua Scenar GB458 6018 G7
Useable Case Capaci: 47.553 grain H2O = 3.088 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Hodgdon H4350 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.468% 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

-04.7   95    40.70   2631    2137   50321   9086     97.9    1.304
-04.2   95    40.90   2643    2156   51036   9124     98.0    1.296
-03.7   96    41.10   2655    2176   51760   9161     98.1    1.287  ! Near Maximum !
-03.3   96    41.30   2667    2195   52495   9198     98.3    1.279  ! Near Maximum !
-02.8   97    41.50   2679    2215   53241   9234     98.4    1.271  ! Near Maximum !
-02.3   97    41.70   2691    2235   53997   9269     98.5    1.263  ! Near Maximum !
-01.9   98    41.90   2703    2255   54763   9304     98.6    1.255  ! Near Maximum !
-01.4   98    42.10   2715    2275   55541   9338     98.7    1.247  ! Near Maximum !
-00.9   99    42.30   2727    2295   56330   9371     98.8    1.239  ! Near Maximum !
-00.5   99    42.50   2739    2315   57130   9404     98.9    1.231  ! Near Maximum !
+00.0  100    42.70   2750    2335   57942   9436     99.0    1.224  ! Near Maximum !
+00.5  100    42.90   2762    2355   58765   9467     99.1    1.216  ! Near Maximum !
+00.9  100    43.10   2774    2375   59600   9498     99.2    1.208  !DANGEROUS LOAD-DO NOT USE!
+01.4  101    43.30   2786    2395   60448   9528     99.3    1.201  !DANGEROUS LOAD-DO NOT USE!
+01.9  101    43.50   2798    2416   61307   9557     99.3    1.193  !DANGEROUS LOAD-DO NOT USE!
+02.3  102    43.70   2809    2436   62179   9586     99.4    1.186  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 5% relative to nominal value:
+Ba    100    42.70   2809    2436   62959   9345     99.9    1.181  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 5% relative to nominal value:
-Ba    100    42.70   2681    2219   52978   9416     97.1    1.272  ! Near Maximum !

 

[longrangehunter]

So Lynn,

That Ba number is rather close to the 1.2282 number for node 5, and the 1.3084 node 6, which be the 42.7 and 40.7 data from your page that are safe. Yet the 4th node is off the page at 1.1016 which would be in the 44-44.5 range if I'm reading the OBT correctly?

Since I had started out with the 42.5 and the 42.7 I assume I was very close to this OBT method for doing this the old school method? At least that's the way it seems since I've never used what you're showing me?

Thanks Lynn

 

[Ridgerunner665]

You are correct....

 

[longrangehunter]

Thank you for your help Lynn. Some very interesting data that should make finding a accurate load a lot easier from the sound of it. I'd be interested in seeing how well this works for my own 280 AI and some Nosler brass with the 168 Berger classic hunters I have. Yet I already have two good loads with the 150 NBT and the 175 Partition, and I'm not sure burning more powder down my barrel testing another load would really make much of a difference. Both those bullets have already taken countless heads of game.

 

[MAinAR]

Someone here posted a load for their 280 Ackley the other day... Nice small group about .5 MOA... But the SD was something like 25 fps I think.... A perfectly good load for anything less than about 800 yards, but beyond that the varying velocity causes the trajectory to fluctuate too much for hunting use... Enough to cause misses on pie plate sized targets.

That was me.

I agree, it not all about the nodes but beg to differ about 25fps ES being unsuitable for longer than 800 yds on a pie plate.

First the 140AB is not going to accomplish the feat of staying on the plate at a 1,000yds on most days anyway, but ES won't be the culprit, the lower BC and the wind is a much bigger issue from my shooting experience when you go "down town".

Having shot a lot of 1000yd setups I judge ES's at well under 1% of velocity to be acceptable for most situations, if extremely accurate and consistent.

Even with a lowly bc of high .4's like the .284 140AB a velocity change of 25fps = 4 inches at 1,000.

50fps difference being 8" but is still on the plate if your hold is perfect and the wind calm. Hardly a miss the plate scenario (but I, no doubt, would prolly miss it as have proven many times LOL).

And regardless of bullet BC the 50fps change will pretty much hang 8" vertical on target at 1,000 because of the difference in MV i.e. the 140 started at 3250 will change vertically from the 50fps speed change the same as a 168LRAB started off at 2950 - 3000 (these from the 27" 280 AI). Again tho is about 8" vertical with either.

Just talking ES in the 280 AI gun. Different animal completely when we discuss real long range guns i.e. guns capable of launching .65+ bc bullets at 3200 + fps, then it starts getting real with vertical dispersions at 50fps es's at under 6.5"

JMHO from launching them.

 

[Ridgerunner665]

I didn't say 25 fps ES....I said 25 fps SD.... Or, roughly translated... 50 fps ES.

A 25 fps ES isn't too bad... I like single digit SD's though.

The load I was referring was using a 168 ABLR.... Might have been JD338's load.

 

[salmonchaser]

Lynn, been following along here with great interest.
The first thing I learned was letting the water sit over night added a full grain in case capacity. I went from 101.75 to 102.9
It will be interesting what kind of difference that will make.
When I had the Jarrett built I specified a 26 inch barrel, a cleaning rod and witness Mark indicates the barrel is 25.25 inches, the node chart shows that will make a difference.
The question I have now regarding nodes, does a muzzle break affect the node figure? When looking at nodes do I use a 27 inch or 25. For ballistics I would use 25 I would think.

 

[Ridgerunner665]

I'm no help when it comes to muzzle brakes....

Barrel length is the length of the entire barrel, this includes the tenon.... Not just the rifled part.

 

[salmonchaser]

I measured to the bolt face, the brake issue has me wondering. The bullet is no longer controlled by the rifling but I wonder if the mass of the brake affects harmonics. Time to experiment.

 

[truck driver]

I do believe I read some where that the point of impact changes when you remove a muzzle brake after sighting in so it would likely change the vibration or harmonics of a barrel how much I wouldn't know.

 

[Dwh7271]

I would agree.
The harmonics would flow to the end of the metal before rebounding.metal would be brake also.

 

[MAinAR]

I didn't say 25 fps ES....I said 25 fps SD.... Or, roughly translated... 50 fps ES.

A 25 fps ES isn't too bad... I like single digit SD's though.

The load I was referring was using a 168 ABLR.... Might have been JD338's load.

I misread and apologize, sure didn't intend issue with it, thank you.

 

[Ridgerunner665]

No problem and no issue... Just clarifying.

 

[muzz]

So my rifle has a muzzlebrake, Should the total length be added to load work up?

I thought it was just barrel length that is rifled that should be considered the barrel.

 

[Wyo7200]

Go by the length of the barrel. Since the brake has no effect on the bullet (constricting or expanding as the shockwave travels back and forth over the bullet) as the bullet passes, the last point of possible contact is the end of the barrel. As previously mentioned Poi will shift, just like when you add a suppressor. Your nodes will possibly be slightly wider due to the dampening, of the wave, but it will still constrict and expand over the bullet.

From Chris longs page:

"What does this stress wave do? Remember that stress is the amount of force or pressure applied to a material, which usually results in the material moving, bending, or displacing. This is called strain. So, the pressure stress from the gasses in the chamber causes a resulting strain in the barrel. Because the stress is applied very rapidly, the some of the stress launches down the barrel as a wave, causing a proportional strain to the barrel as it passes. This strain is initially a slight enlargement of the bore, followed by a slight constriction, eventually dropping off to no change in the bore diameter at all.

As this pulse travels to and fro, it passes by itself, and in the process constructively and destructively adds to itself, all in some predictable way. The shape of the pulse is driven by the pressure/time profile from the propellant burn, and the mechanical properties of the barrel. The theory nicely provides an explanation why very small changes in load parameters could result in large changes in dispersion. If the muzzle diameter is changing very rapidly at a particular time after shot initiation, and if the bullet exits at this time, then very small changes in the load will result in small changes in the exit time, but large changes in the exit direction since the muzzle diameter is always different. Think of this as a dynamic variation of the muzzle crown shape. It is well known that the crown is perhaps the most critical part of the barrel as regards accuracy. So, this theory or model can explain the sensitivity to the load, and explain observation #2 above."

 

[Silentstalker]

I am trying to wrap my head around this thread. I am wondering if someone could tell me more about my rifle/load?

.270 Win.
24" barrel
Win brass
Win primer
150 gr. BT
57 gr. of H4831
Average water capacity of 6 fired cases is 70.78 (pic attached to see if I did it correctly)
My average velocity over a chrony is 2875 fps.

 

[Dwh7271]

Here you go SS.

Cartridge : .270 Win. (SAAMI)
Bullet : .277, 150, Nosler BalTip 27150
Useable Case Capaci: 62.569 grain H2O = 4.063 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4831 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.375% 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

-03.7 98 54.86 2767 2550 50326 11181 96.2 1.273
-03.4 98 55.08 2778 2571 50949 11224 96.3 1.265
-03.0 99 55.29 2789 2591 51576 11267 96.5 1.258
-02.6 99 55.50 2800 2612 52216 11309 96.6 1.251
-02.2 99 55.72 2811 2632 52863 11350 96.8 1.244
-01.9 100 55.93 2822 2653 53518 11391 96.9 1.237
-01.5 100 56.15 2833 2674 54180 11431 97.0 1.230
-01.1 101 56.36 2844 2695 54851 11471 97.2 1.223
-00.7 101 56.57 2856 2716 55529 11510 97.3 1.217 ! Near Maximum !
-00.4 101 56.79 2867 2737 56215 11549 97.4 1.210 ! Near Maximum !
+00.0 102 57.00 2878 2758 56909 11587 97.6 1.203 ! Near Maximum !
+00.4 102 57.21 2889 2779 57612 11625 97.7 1.196 ! Near Maximum !
+00.7 102 57.43 2900 2801 58322 11662 97.8 1.190 ! Near Maximum !
+01.1 103 57.64 2911 2822 59042 11698 97.9 1.183 ! Near Maximum !
+01.5 103 57.85 2922 2843 59772 11734 98.0 1.176 ! Near Maximum !
+01.9 104 58.07 2933 2865 60511 11769 98.1 1.170 ! Near Maximum !

Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 5% relative to nominal value:
+Ba 102 57.00 2952 2902 62315 11600 99.3 1.157 ! Near Maximum !
Data for burning rate decreased by 5% relative to nominal value:
-Ba 102 57.00 2792 2597 51543 11430 94.8 1.256

I'm assuming the barrel is free floated.
Based on 24", Node 5 is at 1.228 plus or minus 2%. Minus the 2% puts the low end of the node at 1.2034 which is exactly where your load is. (yours is at the zero line on the QL above)
What I did to QuickLoad was tweak the Ba (burn rate) to match the average velocity you were experiencing at a given powder charge. From there you get this calc. It's still a little loose as COAL will have a little to do with it and we don't have that.

 

[Wyo7200]

I am trying to wrap my head around this thread. I am wondering if someone could tell me more about my rifle/load?

.270 Win.
24" barrel
Win brass
Win primer
150 gr. BT
57 gr. of H4831
Average water capacity of 6 fired cases is 70.78 (pic attached to see if I did it correctly)
My average velocity over a chrony is 2875 fps.

What is your cases OAL?

If you havent already, take a read through Chris Long's site. http://www.the-long-family.com/optimal barrel time.htm

and take a look at the "nodes": http://www.the-long-family.com/OBT Table.pdf

I take a paper towel and try to remove as much of that convex meniscus of the water. I think its more accurate because you are not guessing if one case has more water (higher menuscus) than another case. If you weigh them with a leveled amount of water, your case capacity will go down, and your loads/ nodes below will be different.

For your rifle and load, I bolded the barrel times that land close to or on a node.
24" barrel nodes: 0.8160 0.8948 1.0221 1.1016 1.2282 1.3084 1.4343

Cartridge : .270 Win. (SAAMI)
Bullet : .277, 150, Nosler BalTip 27150
Useable Case Capaci: 62.569 grain H2O = 4.063 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4831 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0 92 51.30 2581 2219 40979 10390 93.2 1.401
-09.0 93 51.87 2611 2270 42328 10524 93.7 1.380
-08.0 94 52.44 2640 2322 43722 10655 94.2 1.359
-07.0 95 53.01 2670 2374 45166 10783 94.7 1.338
-06.0 96 53.58 2699 2426 46658 10908 95.2 1.318
-05.0 97 54.15 2728 2479 48205 11030 95.6 1.298
-04.0 98 54.72 2758 2533 49805 11148 96.0 1.279
-03.0 99 55.29 2787 2588 51459 11263 96.4 1.260
-02.0 100 55.86 2817 2643 53180 11374 96.8 1.241
-01.0 101 56.43 2846 2698 54955 11482 97.2 1.222
+00.0 102 57.00 2876 2755 56786 11585 97.5 1.204 ! Near Maximum !
+01.0 103 57.57 2905 2811 58676 11685 97.8 1.186 ! Near Maximum !
+02.0 104 58.14 2935 2869 60631 11780 98.1 1.169 ! Near Maximum !
+03.0 105 58.71 2964 2927 62656 11871 98.4 1.152 ! Near Maximum !
+04.0 106 59.28 2994 2985 64754 11957 98.7 1.135 !DANGEROUS LOAD-DO NOT USE!
+05.0 107 59.85 3023 3044 66928 12039 98.9 1.118 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 5% relative to nominal value:
+Ba 102 57.00 2950 2899 62185 11601 99.2 1.158 ! Near Maximum !
Data for burning rate decreased by 5% relative to nominal value:
-Ba 102 57.00 2791 2594 51429 11424 94.8 1.257

 

[Dwh7271]

Whoops Wyo7200, must have been typing when you replied
Sorry for the duplicate