Nodes!

[USAPatriot]

While I've read and understand the ideas behind the optimum velocity 'nodes' for a given bullet/barrel combination, I sure don't pretend to understand the math behind it.

My question is, has anyone taken the trouble to create a small but usable applet that handloaders can use? Generally there's going to be multiple nodes and while my copy of LFDW will tell me what it thinks is one of them, it won't tell me the second, third, fourth,if applicable) etc. Any help? -Rod-

 

[techshooter]

I have not seen an integrated application that combines the necessary internal ballistics modeling with the calculation of the optimum barrel times,OBT : bullet exit times relative to the initial pressure rise time at which the muzzle is the most "quiet" and has the least distortion arising from the pressure pulse induced shock waves). The only solution I am aware of is to use QuickLoad to model the internal ballistics of a load configuration, and matching the resulting calculated barrel time to one of a set of predicted optimum times. An Excel spreadsheet that performs the calculation for the OBT given the barrel length can be found here:

http://www.the-long-family.com/OBT%20tool.xls

If you do not have Excel, you can run the equations yourself on a calculator, although this is a bit cumbersome. They are found at the end of this web page:

http://www.the-long-family.com/OBT_paper.htm

QuickLoad is sold in the US by NECO, and can be found here:

http://www.neconos.com/

David Wilson has put together a nice outline on the load development calculations, which can be found here:

http://mywebpages.comcast.net/davidawilson/LongRange/LR_OBT_Load_Devlp.htm

I am sure that this is more than you wanted, but it seems to be the best way to get to a good starting load, with the best choice of powder and bullet for a given cartridge.

Hope that this helps! Please let me know if I can be of any further assistance with this method.

Cheers,

 

[USAPatriot]

Yeah, the shock wave theory,OBT Paper) plus a comment you made to me in the past is what got me thinking in this direction. I'm looking to get from point A to point B with minimal hassle and hazard. My math ability got left on the pavement in about 1972 so I'm unwilling to try and work the calculations myself.

I'm pretty sure that I have a copy of QL but...

EDIT: I guess I was wrong. I *had* a demo of QL. -Rod-

 

[techshooter]

Rod:

I have calculated the OBT values over a range of lengths and a reasonable set of nodes, and posted them on my site here:

http://www.the-long-family.com/OBT%20Table.pdf

I should have done this long ago. This way, you can simply use a table, and not mess with the equations.

As for QL, there is no substitute at this time, that I know of. I would be happy to run any combinations that you might be thinking about; just let me know.

Cheers,

 

[USAPatriot]

Hmmm. I'm going to have to go back and read the article because I have no clue how to implement the table. I'm curious as to how barrel stiffness,profile) affects the timing? Or is it simply the result of the bullet passage/pressure wave velocity regardless of profile? -Rod-

 

[techshooter]

Rod:

The optimum time is related only to the length of the barrel, and contour has no bearing on this optimum time.

The link above on David Wilson's page tells in detail how to use the OBT time,s) for your barrel together with QL to arrive at a good starting load.

Cheers,

 

[USAPatriot]

Techshooter,

As it turns out I don't have QL after all. It appears I had a demo version at one time. Here's a couple for you when/if you have a chance:

80gr,Berger FB)
70gr,Starke FB)

Both are for a 28" 6BR. Thanks! -Rod-

 

[techshooter]

Rod:

I ran the cases for the 70 and 80 grain bullets, as requested. I didn't have the 70 grain Starke in the database, so I used the 70 grain Hornady flat-base instead. It should make little or no difference in the results. I also assumed that the bullet shank was seated 0.250" into the neck for both bullets.

I apologize for the poor formatting, but the forum editor doesn't like all the whitespace in the original output.

I ran the case to meet the 1.189 mS OBT ext time, which should yield good performance for this 70 grain bullet:

Cartridge : 6 mm B.R. Norma
Bullet : .243, 70, BER MEF
Cartridge O.A.L. L6: 2.135 inch or 54.23 mm
Barrel Length : 28.0 inch or 711.2 mm

Predicted Data for Indicated Charges of the Following Powders.

Matching Barrel Time: 1.189 milliseconds

These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

10 loads produced a Loading Ratio below user-defined minimum of 80%. These powders have been skipped.

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Accurate XMR 4064 105.9 32.9 2.13 3352 99.5 48537 8272 1.189
IMR 3031 97.1 29.9 1.94 3306 99.7 44709 7856 1.190
Accurate No.2520 94.7 32.4 2.10 3302 98.5 46866 8089 1.189
Hodgdon H380 106.3 34.9 2.26 3299 92.9 45190 8792 1.189
Vihtavuori N550 104.7 35.1 2.28 3294 92.7 45354 8803 1.189
Alliant Reloder-15 99.7 32.1 2.08 3280 94.5 46246 8293 1.189
Hodgdon BL-C2 93.0 32.5 2.11 3280 96.8 46585 8199 1.189
Winchester 748 91.4 31.6 2.05 3280 97.4 45068 8102 1.189
Ramshot BigGame 104.7 33.9 2.19 3276 94.5 45055 8481 1.189
IMR 4831 113.4 36.4 2.36 3274 92.0 45427 8680 1.189
Accurate No.2460 93.4 31.7 2.05 3272 98.0 48246 7790 1.189
Vihtavuori N135 100.9 31.0 2.01 3262 99.9 46359 7413 1.189
Winchester 760 104.2 35.4 2.29 3258 88.5 45358 8625 1.189
Hodgdon H335 89.0 31.1 2.02 3258 98.1 45858 7859 1.189
Ramshot Hunter 106.4 36.4 2.36 3257 89.6 45401 8745 1.189
Ramshot TAC 92.4 31.2 2.02 3254 96.7 46237 7905 1.189
Alliant Reloder-10x 85.0 27.3 1.77 3252 100.0 47338 7006 1.189
Ramshot X-Terminator 87.4 29.2 1.89 3252 99.3 46522 7492 1.189
Accurate No.2230 90.4 31.0 2.01 3249 97.8 47866 7609 1.189
Accurate XMR 2015 95.7 28.8 1.86 3247 100.0 47985 7038 1.189
Hodgdon H322 88.9 28.6 1.85 3246 99.3 45394 7446 1.189
IMR 4895 97.7 30.7 1.99 3244 96.2 44317 7968 1.190
IMR 4350 108.3 34.4 2.23 3241 89.0 45269 8420 1.189
Vihtavuori N150 108.6 33.0 2.14 3239 97.7 46371 7798 1.189
Vihtavuori N140 98.9 31.2 2.02 3234 99.1 46355 7484 1.189
IMR 4320 97.1 31.8 2.06 3225 94.3 45157 7895 1.189
IMR 4064 98.8 31.1 2.01 3222 94.5 46419 7736 1.189
Alliant Reloder-12 91.8 30.1 1.95 3222 99.4 46371 7315 1.189
Alliant Reloder-19 115.3 36.7 2.38 3218 85.1 45886 8531 1.189
Hodgdon VARGET 95.7 30.9 2.00 3216 95.1 46056 7730 1.189
Vihtavuori N540 97.6 32.7 2.12 3214 95.4 47516 7807 1.189
Hodgdon H414 100.5 34.8 2.25 3207 85.2 47634 8099 1.189
Hodgdon Benchmark 92.0 29.3 1.90 3198 97.5 47028 7282 1.190
Accurate 2200 81.3 27.6 1.79 3197 98.2 46718 7120 1.189
Alliant Reloder- 7 80.1 25.2 1.63 3195 100.0 50568 6100 1.189 ! Near Maximum !
Vihtavuori N130 89.5 27.8 1.80 3190 100.0 47566 6618 1.189
Vihtavuori N133 93.7 28.8 1.87 3185 99.9 46669 6753 1.190
Hodgdon H4350 111.0 35.5 2.30 3175 83.6 46231 8069 1.189
Vihtavuori N165 119.7 38.5 2.50 3171 86.0 46717 8119 1.189
IMR 4198 84.9 25.2 1.64 3168 100.0 45584 6330 1.189
Hodgdon H4895 94.8 30.2 1.95 3168 95.6 47168 7221 1.189
Accurate No.2700 101.9 34.5 2.24 3154 88.4 48640 7465 1.189
Vihtavuori N120 84.1 25.6 1.66 3151 100.0 47806 5892 1.189
Hodgdon H4198 86.3 25.6 1.66 3147 99.1 46381 6535 1.189
Vihtavuori N160 115.3 37.0 2.40 3146 83.4 47109 7792 1.189
Hodgdon H4831 SC 118.3 38.5 2.49 3142 79.8 47139 8231 1.189
IMR 4227 80.4 23.3 1.51 3112 100.0 46615 5803 1.189

IMR3031 looks like a good candidate, at 29.9 grains. It is close to 100% burned, and yields nearly the best efficiency. There is not enough pressure to get the RL-15 to burn well for this exit time.

Here are the data for the 80 grain Berger:

Cartridge : 6 mm B.R. Norma
Bullet : .243, 80, BER
Cartridge O.A.L. L6: 2.212 inch or 56.18 mm
Barrel Length : 28.0 inch or 711.2 mm

Predicted Data for Indicated Charges of the Following Powders.

Matching Barrel Time: 1.189 milliseconds

These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

9 loads produced a Loading Ratio below user-defined minimum of 80%. These powders have been skipped.

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Accurate XMR 4064 106.1 33.0 2.14 3273 100.0 55552 8061 1.189 ! Near Maximum !
Hodgdon H380 106.6 35.0 2.27 3252 96.5 51471 8973 1.189 ! Near Maximum !
Vihtavuori N550 105.1 35.3 2.29 3248 96.4 51561 9014 1.189 ! Near Maximum !
Accurate No.2520 95.2 32.6 2.11 3234 99.9 53741 8003 1.189 ! Near Maximum !
IMR 4831 113.6 36.4 2.36 3232 95.9 51529 8881 1.189 ! Near Maximum !
IMR 3031 97.9 30.1 1.95 3231 100.0 51668 7672 1.189 ! Near Maximum !
Ramshot BigGame 105.3 34.1 2.21 3229 97.7 51151 8641 1.189 ! Near Maximum !
Alliant Reloder-15 100.4 32.3 2.09 3228 97.6 52706 8447 1.189 ! Near Maximum !
Winchester 760 104.7 35.5 2.30 3222 93.0 51221 8941 1.189 ! Near Maximum !
Ramshot Hunter 106.8 36.6 2.37 3222 94.0 51127 9053 1.189 ! Near Maximum !
Hodgdon BL-C2 93.7 32.7 2.12 3221 99.1 53189 8262 1.189 ! Near Maximum !
Winchester 748 92.1 31.9 2.07 3221 99.5 51596 8123 1.189 ! Near Maximum !
Accurate No.2460 94.0 31.9 2.07 3205 99.7 55025 7759 1.189 ! Near Maximum !
IMR 4350 108.8 34.6 2.24 3205 93.5 51107 8732 1.189 ! Near Maximum !
Hodgdon H335 89.8 31.4 2.04 3197 99.8 52562 7869 1.189 ! Near Maximum !
IMR 4895 98.7 31.1 2.01 3197 99.0 50355 8074 1.189 ! Near Maximum !
Ramshot TAC 93.3 31.5 2.04 3196 99.1 52759 7990 1.189 ! Near Maximum !
Alliant Reloder-19 115.8 36.8 2.39 3189 90.1 51546 8937 1.189 ! Near Maximum !
Vihtavuori N135 101.7 31.3 2.03 3185 100.0 53506 7228 1.189 ! Near Maximum !
Accurate No.2230 91.1 31.2 2.02 3184 99.6 54651 7598 1.189 ! Near Maximum !
Ramshot X-Terminator 88.5 29.6 1.92 3182 100.0 53275 7421 1.189 ! Near Maximum !
IMR 4320 98.0 32.0 2.08 3178 97.6 51306 8071 1.189 ! Near Maximum !
Vihtavuori N150 109.4 33.2 2.15 3178 99.6 53172 7805 1.189 ! Near Maximum !
Hodgdon H322 90.0 29.0 1.88 3176 100.0 52190 7364 1.189 ! Near Maximum !
IMR 4064 99.7 31.4 2.03 3171 97.6 52874 7900 1.189 ! Near Maximum !
Hodgdon H414 101.1 35.0 2.27 3169 89.8 53852 8463 1.189 ! Near Maximum !
Vihtavuori N140 100.0 31.5 2.04 3167 100.0 53225 7408 1.189 ! Near Maximum !
Alliant Reloder-10x 86.2 27.7 1.80 3167 100.0 54388 6897 1.189 ! Near Maximum !
Hodgdon VARGET 96.7 31.3 2.03 3165 98.0 52523 7899 1.189 ! Near Maximum !
Accurate XMR 2015 96.8 29.1 1.89 3164 100.0 55123 6897 1.189 ! Near Maximum !
Vihtavuori N540 98.5 33.1 2.14 3161 98.2 53973 7966 1.189 ! Near Maximum !
Alliant Reloder-12 93.0 30.5 1.98 3153 100.0 53198 7241 1.189 ! Near Maximum !
Hodgdon H4350 111.7 35.7 2.31 3146 88.7 52001 8488 1.189 ! Near Maximum !
Vihtavuori N165 120.0 38.6 2.50 3143 90.9 52463 8458 1.189 ! Near Maximum !
Hodgdon Benchmark 93.4 29.7 1.93 3140 99.5 53689 7362 1.189 ! Near Maximum !
Accurate 2200 82.6 28.0 1.81 3134 99.8 53323 7156 1.189 ! Near Maximum !
Hodgdon H4831 SC 118.6 38.6 2.50 3127 85.7 52569 8746 1.189 ! Near Maximum !
Vihtavuori N160 115.9 37.2 2.41 3117 88.4 53027 8175 1.189 ! Near Maximum !
Hodgdon H4895 96.2 30.6 1.98 3116 98.3 53628 7381 1.189 ! Near Maximum !
Vihtavuori N133 95.2 29.3 1.90 3113 100.0 53917 6647 1.188 ! Near Maximum !
Accurate No.2700 102.6 34.8 2.25 3112 92.6 55080 7740 1.189 ! Near Maximum !
Vihtavuori N130 90.9 28.3 1.83 3110 100.0 54691 6533 1.189 ! Near Maximum !
Alliant Reloder- 7 81.7 25.7 1.67 3097 100.0 58128 6072 1.189 !DANGEROUS LOAD-DO NOT USE!
IMR 4198 86.8 25.8 1.67 3089 100.0 52745 6281 1.189 ! Near Maximum !
Hodgdon H4198 88.0 26.2 1.69 3083 100.0 53104 6529 1.189 ! Near Maximum !
Vihtavuori N120 86.0 26.2 1.70 3061 100.0 55589 5875 1.189 ! Near Maximum !
IMR 4227 82.6 23.9 1.55 3033 100.0 53952 5809 1.188 ! Near Maximum !
Hodgdon H4227 81.4 23.5 1.52 3027 100.0 54498 5681 1.188 ! Near Maximum !

IMR3031 again looks like a good candidate, at 30.1 grains. It is 100% burned, and again yields nearly the best efficiency. Accurate 2520 at 32.6 grains would also be a good choice.

Keep in mind that these numbers are just predictions based on a nominal set of parameters for case volume, bullet seating depth, and other factors, and do not take into account the real world variations in bore size, bullet size, lot-to-lot powder burn rate variance, and other unknowns. I recommend that you start back by at least 1.5 grains, and work up carefully, very carefully. I have had very good results with QuickLoad, but there is no substitute for caution when trying out a new load combination.

Hope that this helps!

Cheers,

 

[USAPatriot]

Chris,

Thanks. That's a LOT more info than I expected to see. Pretty amazing. It's a shame that LFDW isn't that versatile, though it's a damned good program in it's own right.

Interesting about the burn times for 3031. It's one of my favorite powders, no doubt about it. And just this evening I was pondering whether or not it could be predicted whether a given powder pushing a given bullet down a barrel with a specific length would burn itself out short of the muzzle or outside the muzzle. Apparently so, huh? How did you arrive at that? That brings up other questions too that are outside the scope of this thread though. Great info that I'll be eager to test out. I'm hoping my backordered N135 will be arriving 'soon'. Sinclairs said they'd be getting it in in November. Time's about to run out on that particular clock. -Rod-

 

[techshooter]

Rod:

It's hard to see in all that data since the forum editor messed up the white space, but the percent completeness of the burn is one of the primary outputs from QuickLoad. I have taken the liberty of posting the QuickLoad output on my web site for you to look at, with the editing intact:

www.speakeasy.net/~cdlong/quickload_example_output.pdf

For the 70 grain bullet case, and you can see that the 3031 is 99.7% burnt at the muzzle.

QuickLoad is definitely one of the most useful addition to a serious reloader's toolkit, as it allows really solid selection of powders before even dropping one grain in a case, and saves a huge amount of range testing time.

Please, let me know if I can be of further help in any way. Good luck!

Cheers,

 

[USAPatriot]

Rod:

It's hard to see in all that data since the forum editor messed up the white space, but the percent completeness of the burn is one of the primary outputs from QuickLoad. I have taken the liberty of posting the QuickLoad output on my web site for you to look at, with the editing intact:

www.speakeasy.net/~cdlong/quickload_example_output.pdf

For the 70 grain bullet case, and you can see that the 3031 is 99.7% burnt at the muzzle.

QuickLoad is definitely one of the most useful addition to a serious reloader's toolkit, as it allows really solid selection of powders before even dropping one grain in a case, and saves a huge amount of range testing time.

Please, let me know if I can be of further help in any way. Good luck!

Cheers,

That's much easier to read, thanks. Does QL's output allow for alternating the lines with different background colors for easier reading?

It doesn't matter much though. It's price tag is far out of my reach these days. -Rod-

 

[techshooter]

Rod:

Unfortunately, no, it does not have the formatting flexibility. However, you can export the data directly in Excel, and manipulate it any way you want using the spreadsheet tools.

Cheers,

 

[USAPatriot]

Lynn,

Any data really that will narrow the field. I have LFDW and it does a good job of handing me data to work with but it's really not predictive software in the sense that Techshooter has been describing Quick Load.

By all means if you have something to add, feel free. I've been chasing the one-hole for 20 years and while the size continues to shrink, we both know it's never good enough and never will be. My record 5 shot group is .107. I'm looking to beat it of course -Rod-

 

[USAPatriot]

Techshooter,

Just out of curiosity,,and only if you just happen to have time to kill) do you have figures for a sub-sonic load for the above? Everything the same,6BR, 70's and 80's, 28"). Nah not 70's, how about just the 80's and Scenar 90's. If it's not worth your time, no problemo. Thanks! -Rod-

 

[GWN]

Techshooter,
When using the table for barrel length, would you measure to the end of an attached muzzle brake or just to muzzle of barrel?
Thanks,
George

 

[USAPatriot]

George,

I think techshooter would agree that you're only going to count the rifled section of barrel, not the brake and not the chamber. -Rod-

 

[techshooter]

Rod:

I have been without power since Thursday night - got hit by a big windstorm here in Seattle, and living out in the sticks means that we are the last to get lights back. We are on generator for a bit to keep the fridge and freezer cool, and us warm. I didn't see your request until now. I'll try and work on it and get back to you.

George:

Use the length as measured from the muzzle crown,without brake) to the bolt face. The length of the chamber is accounted for in the equations.

Cheers,

 

[USAPatriot]

Chris,

I thought as much. I know what it's like being last in line. I hope you're able to stay warm, anyway. No hurry on the data. -Rod-

 

[USAPatriot]

Bump

 

[techshooter]

Rod:

Sorry! - flat forgot your request - I got busy at work, and forgot all about it.

I don't think that a subsonic load is feasible with the 6BR. I can't get QL to provide a solution below 1000 FPS with realistic shot start pressures. Even 8 grains of Bullseye will push a 107 MatchKing at over 1600 FPS from that 28" barrel!

Interesting idea, in any case.

Cheers,