OCW, Ladder Loads, Accuracy Nodes with Velocity...Blew a fuse.

[Sticks]

All my shooting and reloading prior to 6.5 Grendel was good enough to insure consistency and accuracy to 100y...really never had anyplace to shoot farther, or need, let alone time with work.

Since my foray into 6.5Grendel and making a point to get involved with long range shooting and competitions, I know my reloading has got to be spot on.

Every day, I read here, and do more research as time permits.

I never heard of OCW vs Ladder testing until someone posted here, and I get the logic behind it (actual ladder testing - turns out I was doing OCW all the while), providing one is a good enough shot not to botch a shot and skew your results.

So....I tried the proper way to do a ladder load test in .3gr increments of AA2230, AA2520, and CFE,
Hornady Once fired brass
Sized -.003 bump on shoulder
Neck tension only with a .288 bushing
Trimmed at 1.515
COAL at 2.265
CCI BR primers
Hornady ELD 123gr
Rifle is a PF Upper - 18" Barlitien barrel.
Shots taken at 200 yards. Results are inconclusive.

Aside from my observed drift with loads up and right as the powder charge goes up, 2230 and 2520, disregarding left/right all the holes are stacked one on top of the other in a string in a seemingly random order for all 3.

From my OCW 5 round shooting, there were no distinct "nodes". In fact the only nodes that I have seen were from my Moscow Match testing, and there were 2 distinct nodes. One on the bottom velocity end, and one at the top that was flattening primers, but avg velocities on a .3gr increment were within 2 FPS (I gotta say I am in love with those groups too).

Some of the MOA numbers below I tweaked a little to remove a single outlier that would take a sub .75 MOA and push it out to over 1.10.

Charge	Average FPS	SD	ES	MOA	+/-
CFE
28.4	2271	25.4	56	.665
28.7	2286	17.1	41	.635	15
29.0	2311	9.4	21	.722	25
29.3	2409	7	19	.929	98 Pressure spike?
29.6	2420	18	47	1.039	11
29.9	2429	16	20	.918	9
30.2	2443	13	36	.723	14
30.5	2450	20	49	.650	7
30.8	2480	7.5	17	1.308	30
31.1	2519	12.1	32	1.225	39 Spooky compressed
2230
26.2	2333	14.3	36	.765
26.5	2353	8.8	22	.622	20
26.8	2389	17.9	46	.598	36
27.1	2435	8.3	23	.878	46
27.4 MAX	2472	13.8	38	.431	37
27.7 HOT	2499	12	32	1.204	27
2520
28.1	2339	17.6	46	1.259
28.4	2366	7	14	1.065	27
28.7	2379	8	16	1.079	13
29	2430	6.6	18	.988	51
29.3	2450	3.4	9	.864	20
29.6 MAX	2480	7	23	.845	30
29.9 HOT	2506	7	16	.783	26

The only good velocity node that I am seeing is at the 2450ish for CFE. Am I wrong to try to push the powders that I have selected to be on par with Hornady 123 ELD? I can't believe that I am not getting any for 2230 or 2520.

Suggestions, advice...anything? Right now I am loading 2230 (I have 24# of it from my 5.56 days) at 27.4gr based on groups size and 2470ish velocity.

[fdbyrne78]

I've been having similar issues finding the right load for my rifle.

I read all of the details about the OCW method and something struck me as odd. With barrel harmonics being subject to the same speed through steel, shouldn't all barrels of the same length made of the same type of steel have the same OCW results for a given powder and bullet? After reading the OCW details twice, I just can't see why not.

If I'm right, knowing the results of another shooter's OCW load will a given powder, bullet, and 20" stainless barrel would keep all others with the same setup from having to repeat the process.

Edit: Now that I'm thinking about it even more, I have a fundamental doubt about the OCW method. The idea is that the shockwave travels at 18 fps from the chamber to the muzzle then back. The goal is to have the bullet leave the barrel while that shockwave has made the journey and is back at the chamber end. How the hell is that even possible if the shockwave travels at 18 fps (speed of sound through steel) but the bullet is traveling WAY faster. Shouldn't the bullet have already left the muzzle by the time the shockwave made it to the muzzle for the first time much less travel back to the chamber end?

[grayfox]

The pressure wave (shock wave if you will) travels through steel at 18,000 ft/s, not 18. It typically makes 5-7 round trips/ reflecting off each end as it travels. It is relatively constant in steel so the statement about barrel lengths is correct as far as the pressure wave is concerned.
The idea is to "time" the bullet exit by adjusting powder load, and therefore exit velocity and bullet travel time, so that the wave is somewhere back close to the breach when you have bullet exit - this way the barrel muzzle is not only "quiet" but also consistent in size and position during bullet exit. Other factors play into it such as powder charge, bullet acceleration (different powders affect this) vs time, and the barrel's unique friction and even chamber geometry - acting against the bullet. This all happens in microseconds and milliseconds. So load performance won't be exactly the same from barrel to barrel or rifle to rifle, but in general for most cases those results should bunch together around a given velocity, or velocity range (the "node"). Steel pipe is steel pipe.

Of course brass type and volume, and other ballistic variables will have their impacts as well.

For 22" barrels bullets and powders, lots of centerfire rifles tend to have a node somewhere close to 2700 ft/sec.
I have used an empirical formula with barrel length, exit velocity and COAL as the major inputs to narrow down the powder charge ranges I try, and have found some very good shooters and consistent nodes. I combine this with chrono testing because, as you mention, I'm not expert enough to avoid those flyers... too many fliers in the ointment so to speak.
However, for me this method of looking at nodes and this formula is working fine.
I wrote a small white paper, but all the credit for the idea really goes to Chris Long:

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

This method works for me, others use the OCW and still others use various single load/single shot methods very well.

I didn't see a barrel length for your grendel but with cfe lots of rifles have accurate loads at about 2470-2510 ft/s for 18" barrels.

Relative barrel friction differences can bump that ocw length up or down a bit.

[Bobke]

GF
Do you have a quick summary of ideal muzzle velocity and barrel lengths from 16-24” you could offer? Does that stay somewhat constant relative to bullet weight? Would not think entirely so, but would appreciate you sharing what you know in that regard. Good stuff.

[fdbyrne78]

Thank you. That makes sense. The web page that I saw the OCW description on listed the shock velocity at 18.000 fps. That sounded slow, but I didn't question the period separator vs the traditional comma since we are all reloaders and are used to expressing things to the 3rd decimal place.

[LR1955]

Sticks:

I agree totally with your findings. A good barrel will shoot most any well made bullet very well. How to find the right load given you have a well made rifle and barrel? Pretty easy. Find out what the majority of the competitors in the sport are shooting and start with that load. Most likely it will be in the high end of the velocity scale for the cartridge. Probably not maxing out but around 90% of maxing out. Load five, five more a grain less and five more a grain heavier in powder. Print on paper at 200 and figure out which one shot the best. Load twenty and shoot a course of fire in your sport. They will probably perform well enough for you to win with providing you are a good marksman.

LR55

[bj139]

It looks like the load you are already using is the best among these 3 powders.
Are you going to try XBR-8208?

[grayfox]

GF
Do you have a quick summary of ideal muzzle velocity and barrel lengths from 16-24” you could offer? Does that stay somewhat constant relative to bullet weight? Would not think entirely so, but would appreciate you sharing what you know in that regard. Good stuff.

It's not totally plug n chug, I'll confess I'm still working on it. I haven't done an IMV as a function of barrel length... instead I try to find barrel times for a given length. example, my 18" AR, I've found MV's at nodes of approx 2500-2515, 2415-40, 2650-2690. these are actual measured speeds for my AR. when I switch to a different rifle, in this case my 20" howa, naturally I expected the MVs to be slightly different. But since a) it's a diff length, b) a diff barrel with diff friction, throat, etc effects, and c) bolt vs AR (possibly has some effect IMO) I can't really say MV vs barrel lengths.

In the Chris Long paper and elsewhere a couple of barrels were shot and then cut back an inch at a time as part of his OBT theory. Chris has a couple of graphs that are very interesting on that.

How much does MV change as a function of barrel length? answers seem to vary from 15 f/s/inch to 50 f/s/inch... for the three rifles I've been tracking I can find decent nodes for the given barrel.

Full disclosure I don't have thousands of rounds over several calibers and several years like some of the really pro shooters on here. I try to temper my findings with their wisdom - but the theory and possibilities do kind of excite me, engineering-wise.

[VASCAR2]

Sticks curious where you got your data for Accurate 2230. Western’s online data shows a max charge of 27.4 grains of A2230 with a 123 grain SMK with a velocity of 2424 FPS out of a 20” barrel with pressure of 51435 PSI.

[ricsmall]

Try some 8208 XBR. It shoots phenomenal groups with everything from 100 grain up to 123’s. Haven’t had any terrible groups with it. The best are at book max on 100 nosler BT and 123 of any flavor except the custom comps. They like 27 grains outta my gun.

Richard

[grayfox]

In the cfe world for 123's I've found my best velocities 30.7-31.4 range. Again individual barrels will vary.
CFE likes to be pretty much at max fill IMO.
My 18-er, 30.8 at 2510 f/s, howa 31.4 at 2529 f/sec. In my hands I can get 0.5/0.75 with the standard noob-flyer, so 80% within 1 moa at 100 yds for either rifle. ok, sometimes 1.25...
I'm working with 8208 now for my 100 grainers.

[RiverRider]

If you guys are discussing what I THINK you're discussing, you cannot find the OBT sweet spot for a powder and then tune a load with a different powder to the same velocity and expect the same results. Barrel time with two different powders will be different even with the velocities perfectly matched. The pressure curves will differ enough to result in significantly different barrel times.

[grayfox]

I think that's partly true, however for 2 powders that are very close in performance for a caliber/bullet (ex, varget and RL-15 for 123 gr in 6.5 CM, 20" barrel), those two seemed to be pretty close at 36.9/2628 (RL15) and 36.6/ 2625 (Varget). BUT, I liked H4350 better (slower and different pressure curve) at 41.1/ 2606 ft/s. Note all of the 3 were in a node range of 2600-2625, yet personally I found the H4350 load to be a bit better for me. I don't know that one could generalize however so RR you may have a good point.
Food for further thought: for a different bullet, the 129 ABLR, in my 20" CM, I use RL17 and guess what the velocity is? 2597 ft/sec.
the caveat of ymmv still applies.

[RiverRider]

I just ran QuickLOAD to supply an illustration of what I am saying. For a barrel of 22.2 inches, 1.137 milleseconds is supposed to be an OBT node. All these different powder charges provide 1.137 milliseconds of barrel time. Of course, not all are usable...some exceed the 62000 psi limit for the 6.5 Creedmoor.

Cartridge          : 6.5 Creedmoor Hornady
Bullet             : .264, 143, Hornady ELD-X 2635
Useable Case Capaci: 46.275 grain H2O = 3.005 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length      : 22.0 inch = 558.8 mm

Predicted Data for Indicated Charges of the Following Powders.
Matching Barrel Time: 1.137 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 !

Powder type          Filling/Loading Ratio  Charge    Charge   Vel. Prop.Burnt P max  P muzz  B_Time
                                      %     Grains    Gramm   fps     %       psi     psi    ms
---------------------------------  -----------------------------------------------------------------
Alliant Reloder-26                 105.9     48.6     3.15    2865   100.0    60561   12130   1.137  
Norma MRP                          106.6     47.5     3.08    2835    99.3    60794   12175   1.137  
Hodgdon Retumbo                    120.9     51.9     3.36    2823    99.5    59459   12402   1.137  
Alliant Reloder-25                 114.3     48.5     3.14    2821   100.0    59959   11765   1.137  
Vihtavuori N560                    108.2     47.1     3.05    2815    96.7    60677   12291   1.137  
Accurate MAGPRO                    108.8     49.3     3.20    2814    95.3    61179   12343   1.137  
Alliant Reloder-22                 108.8     46.9     3.04    2807    98.4    61273   11925   1.137  
Winchester WXR                     111.7     47.1     3.05    2807    98.3    61333   11937   1.137  
Alliant Reloder-23                 111.9     46.7     3.03    2798   100.0    61679   10877   1.137  
Alliant Reloder-17                  95.8     42.9     2.78    2791   100.0    61391   10744   1.137  
Accurate 4350                      101.1     43.1     2.80    2786   100.0    65276   10603   1.137  
Alliant Reloder-16                 103.2     42.9     2.78    2786   100.0    62816   10633   1.137  
IMR 7828 SSC                       106.1     46.5     3.01    2784    96.9    60034   11831   1.137  
IMR 7828                           112.1     46.5     3.01    2784    96.9    60034   11831   1.137  
Ramshot Hunter                     101.0     44.5     2.88    2774    99.8    62347   11063   1.137  
Winchester 760                      95.6     43.1     2.79    2774    99.5    62741   11074   1.137  
Hodgdon H414                        95.6     43.1     2.79    2774    99.5    62741   11074   1.137  
Vihtavuori N550                     98.4     42.9     2.78    2773   100.0    63868   10761   1.137  
Accurate 3100                      110.5     47.2     3.06    2770    99.9    65353   10666   1.137  
Ramshot Magnum                     107.8     50.1     3.24    2769    98.7    60390   11375   1.137  
Norma URP                          101.0     42.6     2.76    2766   100.0    63336   10606   1.137  
Alliant Reloder-19                 105.2     44.9     2.91    2765    98.3    61627   11323   1.137  
IMR 4831                           106.5     43.5     2.82    2762   100.0    64380   10397   1.137  
Hodgdon H1000                      116.4     49.1     3.18    2749    96.7    60008   11506   1.137  
IMR 4895                            91.5     39.0     2.53    2745   100.0    64360   10117   1.137  
Norma 203 old                       94.8     40.9     2.65    2744   100.0    65998    9892   1.138  
Norma 204                           99.8     44.0     2.85    2743    98.1    61978   11011   1.137  
Ramshot Big Game                    91.4     41.5     2.69    2740   100.0    63408   10090   1.137  
Hodgdon CFE223                      86.4     41.0     2.66    2740   100.0    63541   10065   1.137  
Hodgdon H380                        93.8     40.9     2.65    2739   100.0    64719   10252   1.137  
Alliant Reloder-15                  92.3     39.4     2.55    2738   100.0    64332   10085   1.137  
Norma 203B                          92.9     39.6     2.57    2737   100.0    64509   10010   1.137  
Hodgdon BL-C2                       87.5     40.7     2.64    2734   100.0    64952    9891   1.137  
Hodgdon H4831 SC                   106.1     45.8     2.97    2731    96.3    61439   11061   1.137  
Hodgdon H4831                      110.4     45.8     2.97    2731    96.3    61439   11061   1.137  
Accurate 4064                       95.8     40.0     2.59    2731   100.0    68849    9341   1.137  
Vihtavuori N165                    111.4     47.0     3.05    2730    98.8    62747   10606   1.137  
Hodgdon Hybrid 100V                103.7     42.8     2.77    2728   100.0    63307    9753   1.137  
Winchester Supreme 780             103.8     46.7     3.03    2726    98.2    62185   10752   1.137  
Hodgdon H4895                       89.2     38.1     2.47    2720   100.0    64465    9772   1.137  
Hodgdon H4350                      103.0     43.0     2.78    2718    99.1    62851   10458   1.137  
IMR 4350                           101.1     42.9     2.78    2718    99.1    62872   10439   1.137  
Ramshot Wild Boar                   87.5     39.9     2.58    2717   100.0    63885    9850   1.137  
Accurate 2520                       88.2     39.7     2.57    2715   100.0    66712    9304   1.137  
Winchester 748                      84.8     38.9     2.52    2715   100.0    64259    9516   1.137  
IMR 4007 SSC                        95.4     41.3     2.67    2714    99.2    64228   10339   1.137  
Accurate 2495                       90.6     37.8     2.45    2711   100.0    69885    9008   1.137  
IMR 4955 Enduron                   107.7     44.7     2.90    2709    96.7    62435   10752   1.137  
Vihtavuori N160                    111.2     45.5     2.95    2706    97.2    62723   10527   1.137  
Ramshot TAC                         87.6     40.3     2.61    2705   100.0    63825   10033   1.137  
IMR 4320                            93.5     39.2     2.54    2702   100.0    62699    9679   1.137  
IMR 4451 Enduron                    96.6     40.7     2.64    2700    99.4    62922   10238   1.137  
Norma 201                           91.4     38.1     2.47    2700   100.0    65972    9395   1.137  
IMR 3031                            92.2     36.8     2.38    2698   100.0    65531    9069   1.137  
Hodgdon VARGET                      94.6     39.0     2.53    2692   100.0    63249    9713   1.137  
Accurate 2460                       84.8     38.9     2.52    2692   100.0    66953    9098   1.137  
IMR 4064                            95.5     38.5     2.49    2691   100.0    63902    9529   1.137  
Vihtavuori N530                     86.2     37.0     2.39    2689   100.0    64340    9364   1.137  
Vihtavuori N150                    102.0     41.1     2.66    2688   100.0    65461    9237   1.136  
Accurate 2230                       84.2     38.9     2.52    2685   100.0    65801    9172   1.137  
Vihtavuori N540                     92.7     40.0     2.59    2684   100.0    65425    9260   1.137  
Norma 202                           90.5     38.0     2.46    2682   100.0    65663    9087   1.137  
IMR 8208 XBR                        88.1     37.6     2.44    2682   100.0    64249    9275   1.137  
IMR 4166 Enduron                    96.0     39.2     2.54    2681    99.4    63347    9911   1.137  
Ramshot X-Terminator                85.7     39.0     2.53    2680   100.0    64364    9406   1.137  
Hodgdon H335                        81.4     37.9     2.46    2677   100.0    64956    9092   1.137  
Accurate 2700                       95.7     42.6     2.76    2675    99.1    64778    9772   1.137  
Vihtavuori N135                     99.1     38.3     2.48    2659   100.0    67039    8559   1.137  
Hodgdon H322                        86.1     35.7     2.31    2658   100.0    64643    8803   1.138  
Vihtavuori N140                     92.6     38.7     2.51    2656   100.0    65644    8750   1.137  
Alliant AR-Comp                     88.2     36.4     2.36    2654   100.0    66991    8456   1.137  
Hodgdon Benchmark                   87.7     36.8     2.39    2646   100.0    64496    8861   1.137  
IMR 7977 Enduron                   112.2     47.3     3.07    2641    89.0    63320   10146   1.137  
Alliant Reloder-12                  86.5     37.6     2.44    2641   100.0    65337    8634   1.137

[RiverRider]

Compare the velocities between Re17 and Re15. Same barrel time, but velocities differ by 53 fps. This is what I'm talking about.