6.5 PRC Powder Charge/Velocity Ladder Test. No Flat Spot

[Danny1030]

In my opinion, you don't need a velocity flat spot. That is super hard to tell with a single shot in each charge weight anyway.

You want a vertical dispersion flat spot. And testing should be done at 400-600+. Look for 3-4 in a row that have very little vertical. That is where your node is.

I agree with Lance. Attached photo was a 6.5 PRC ladder test with 140 Elite Hunters in once fired Lapua. All rounds fired from 615yds. ES is around 20fps but shoots well at 59.0 grns.

 

[Stonyman88]

In the past year I feel like load development has become as controversial as barrel break in. I most often find what you did, no velocity flat spot. Some look for smallest group, some best ES and for Satterlee method similar vertical dispersion (positive compensation). If it were me and loads 8-9 were safe from max I'd split the difference and if good groups then Bob's Your Uncle. Some would do a bullet depth seating, to me if groups do what you want no need. Easy to shoot out a barrel overthinking load development.

Yes Bob is your Uncle, love it, lol

 

[Stonyman88]

My buddy and I have been working together on load development for our rifles; his is a 6.5 PRC. In load testing I found a velocity flat spot with my 243, also with good POI, but he has not.

Twice now with once-fired Lapua, his powder charged different loads have tracked Gordons Reloading Tool almost exactly. No nodes. The first ladder was 0.010 off the lands with a IMR7828SSC. The second, ladder was with H4831SC, and 0.070 off the lands. He's using Fed 215M primers, producing ~50 ft/sec higher velocities than non-magnum primers (which GRT predicted), and 147 gr ELDM's. At test range of 100 yds, he produced the lowest vertical dispersions with loads 2, 5, and 7 (see chart below); and corresponding velocity SD's of 12.0, 8.9, and 4.6.

Questions:
With 0.6 gr between loads, why were there no discernible velocity flat spots, see graph - average velocities linear with powder charge increments?
He's got a carbon barrel--does the carbon damp out the harmonics/resonance of the barrel? We'd appreciate any advice you can lend.

Velocity Curve vs H4831SC w/ GM215M primers
View attachment 511077

Vertical dispersion - ignore Load 1 and load 10
View attachment 511078

Not sure what your looking to do, shoot for speed or accuracy , I just shoot for accuracy, and like a med. speed, I've been using AL26 & H1000 and shoot with .5 load up at a time, then when I find a good group, I go to distance off the lands, start at 15 and go to 60 + Amazing the difference in bullets, ELD-M like just under 50 but others like 25 off the lands. The best groups at 100 yds. is under .250 like one hole groups. It's a Bergara with 22" barrel

 

[Stonyman88]

I agree with Lance. Attached photo was a 6.5 PRC ladder test with 140 Elite Hunters in once fired Lapua. All rounds fired from 615yds. ES is around 20fps but shoots well at 59.0 grns.

Very well at 615 with 59.0 , but what powder , H1000 or AL 26 ? Or did I miss the powder?

 

[DallasLR]

Gentlemen,

It hurts. Most of us have spent unthinkable time doing tests that simply are not statistically significant. If you want the data you can read all of Bryan Litz's books. I would start with his series called Modern Advancements in Long Range Shooting.

There is also a guy on YouTube who has built computing tools to statistically validate the same findings. His website is https://blackburndefense.com/

No matter what you think you have seen or what others think they have seen you have to shoot close to 50 rounds for an outcome to become statistically relevant. You just can't do ladder tests with that many rounds. And those that have, like myself, paid the price in components and barrels to try and save you from doing the same. Seating depth, powder charge, barrel harmonics, and even primer seating depth do not create more precision for any CONSISTENT combination. Ever single combination will have a different impact point but no single combination over another will be more precise (Eg hit that impact point more consistently). Moral of this story for those willing to listen: Pick a combination and spend your time and money replicating that exact combination for every single round. Shoot 15-20 rounds of it. Sight your scope and you will have a gun that is as accurate and as precise as that gun and those components can be. If that is not accurate enough for you do the same with "better" components. If that doesn't get you the precision you need buy a heavier gun.

Finally, if you see flyers it is most likely you. The barrel moves before the bullet leaves the barrel. It is unimaginably hard to consistently control this and is logarithmic to gun weight. Even a rail gun bolted to concrete will have changes if even a single mechanism, bolt, or comment deviates.

 

[Danny1030]

Very well at 615 with 59.0 , but what powder , H1000 or AL 26 ? Or did I miss the powder?

N565

 

[Stonyman88]

N565

Thanks,

 

[Tommy T]

I have a Bartlein 26" carbon barrel and all of my shooting buddy have carbon barrels in the 6.5 Prc from 20" to 26" and they all shoot great out to 1200 yds I have 55.6 gns. Of RL 26 but the Hornady eld match works great as well

 

[gregmark24]

Thank you for your posting. Where did you find a batch of 1000 bullets? All my favorite suppliers only sell 100 at a time with no guarantee they're from the same lot

 

[BrentM]

@gregmark24, I have several carbons and feel like they are similar to any bull barrel. I personally find them easy to tune but for me they handle strings of fire better than a similar weight steel barrel.

 

[Phil Rizzo]

The varmint contour SS I have seems awful tight in the bore, I may try a CFW Bartlein before long.

 

[FURMAN]

If you loaded 30 shots of each powder charge and shot all over a chronograph you would not see a flat spot. When you do see a flat spot it is because you do not have a statistically significant set of data. These tests are a waste of barrel life and components. If you are not shooting at a paper target you are not doing statistically valid load development. I have graphed this over the last 100 plus load developments and there is no correlation to a small group at longe range and the "flat spot" from 1-3 shots per powder charge. I don't know why this "method" continues to be perpetuated.

 

[lancetkenyon]

Thank you for your posting. Where did you find a batch of 1000 bullets? All my favorite suppliers only sell 100 at a time with no guarantee they're from the same lot

Buy two 500 ct from the same lot. I recently purchased ten 250ct boxes of same lot Berger 215 Hybs.
Some of the smaller Bergers (.224 85.5 Hyb) can be had in a 1K box too.

250/500/1000ct boxes are pretty common for Berger and Sierra.

 

[gregmark24]

I haven't been able to find 500 or 1000 count for Hornady (yet).