OCW node and harmonic proof, comments please!

[308sako]

The rifle is a .308 Winchester Rock Creek 5R barrel at 26.5" in length, Action a Rem 700, Jewell 2 oz trigger and Tubb FP spring. Optic is an 8.5 X 25 Leupold LRT with a fine duplex. Stock is the HS precision factory with bedding block. Rifle is a good shooter and this particular test was to determine which load was a better shooter based on only the charge weight was different. Remarkably the Oehler chronograph recorded only a one foot per second difference between these two groups. With the 42.7 grains yielding 2619 sd of 17 and the 43.0 grain charge giving 2618 ft/secs and SD of 5. Actual firing conditions favored the top group slightly as the wind was inconsistent in the first lower group. Bullet 185 Berger, powder Varget, primers Federal 210 match grade. Cartridge overall length for my chamber 2.922".

What this showed me was how important internal aspects of ballistics are as sheer velocity is not the only answer to precision shooting.

 

[Dan Newberry]

True... lots of folks will shoot a lot of shots over a chronograph and go with the tightest numbers, assuming that load will be the best performer.

But the target is always the final arbiter.

 

[Dacam]

Thats also some great shooting by the way. Im shooting the same specs in my AIAE MKIII, 24" Lothar Walther 1/12 twist, 185 Berger Juggies, Lapua brass, 210m, 43.0 Varget, 2.915 oal, -.030 jump.

 

[woostri]

Ahh the ocw testing. Many hours I've pondered over results. The data recording gets more and more detailed and the results get more and more obscure.... But it sure is fun. I like the fact that you tested at 400 yards. Much easier to interpret. I'm stuck at 90 yards right now.... Who makes an outdoor range 90 yards anyways, sheesh.

--- aim small miss small ---

 

[plh]

I want to thank you for submitting this. One occurrence does not establish an undeniable truth but your demonstrated results at distance will allow me to be a little more at peace with diverging group and chronograph results. I've been wrestling with this issue with the same bullet and powder combo.; 185 Berger OTM, Lapua brass neck-turned to a fare-thee-well, 42.9 Varget, 210M, .020" off the lands, 2610-2625 fps MV, 24" 1:10 twist. Excellent groups (.3"-.4" at 200 yrd) with ES of 20-30, SD of 10-18, give or take, marginal groups (.7"-1.0") with single digit ES/SD's after very minor adjustments to good grouping load (repeated to insanity). Opportunities for extended distance are rare and not chrono'd. I guess one could consider taking the low chrono. settings gained by seating depth tweaks and such and tighten things up with a barrel tuner. I'm not interested in spinning that plate. You listed OAL but perhaps you could provide distance from the lands.
Pete

 

[FunkBass2008]

That's a big difference. I came across the same thing when I started loading, I always tried to get the fastest possible load that was safe and stick with it. Then I dropped it down 50-100 fps and saw some big accuracy gains.

 

[Mike]

tag

 

[bodywerks]

The rifle is a .308 Winchester Rock Creek 5R barrel at 26.5" in length, Action a Rem 700, Jewell 2 oz trigger and Tubb FP spring. Optic is an 8.5 X 25 Leupold LRT with a fine duplex. Stock is the HS precision factory with bedding block. Rifle is a good shooter and this particular test was to determine which load was a better shooter based on only the charge weight was different. Remarkably the Oehler chronograph recorded only a one foot per second difference between these two groups. With the 42.7 grains yielding 2619 sd of 17 and the 43.0 grain charge giving 2618 ft/secs and SD of 5. Actual firing conditions favored the top group slightly as the wind was inconsistent in the first lower group. Bullet 185 Berger, powder Varget, primers Federal 210 match grade. Cartridge overall length for my chamber 2.922".

What this showed me was how important internal aspects of ballistics are as sheer velocity is not the only answer to precision shooting.

Have you duplicated the results with several additional groups with the two different powder charges?
I ask because I have shot groups with a box of handloads of the same charge, etc. One group is a ragged hole and another will be over twice the size.
My point is that I wouldn't draw this conclusion until I could duplicate it.

Sent from my SCH-I545 using Tapatalk

 

[308sako]

plh, about .010" off the lands

Bodywerks, This was the third time shooting this load (42.7 grs) and it has repeated this level of precision, i.e., under .35 MOA in my rifle. The 43.0 attempt showed me that while the muzzle velocity was virtually identical and the SD was lower, and conditions were better; still the load did not shoot (to my standard.) Barrel time and harmonics is what I am mainly referencing here in the original post.

Hope it expands the understanding.