Home Forums Hunting & Shooting Long Range Hunting Ballistic Coefficient discussion

While not charged with a Lee Dipper, these loads were all thrown with a Quick Measure, not trickled, and not weighed individually. These groups won't win any BR records, but I doubt that observed results would improve noticeably by increasing the precision of my powder charging technique.

Yes it can, except most people don't have the ability, equipment, or desire, to do so.

Here's 2.3" 1000 yard BR target:

It really comes down to accuracy requirements vs. time/volume of ammo production. For plinking, throwing a good load with my QM can get right around 0.5MOA accuracy or better, as shown in the group pics above. That is with a variety of barrels, ranging from factory to top end. But if I'm going to a LR competition, I'll take the time to weigh each charge with scrutiny. Same with the BR game, the accuracy requirements are higher, and the need to produce ammo in high volumes is lower.

Interestingly, the chrono results Rick quoted above show more meaningful SD values than most. When we start to get 30-50+ shots included in an SD calculation, that increases the confidence in the sample representing the load's performance. I think most guys who claim tiny SD's based on a few shots over the chrono, would be disappointed if they kept shooting until they had 30 rounds measured and factored into the SD value.

While I agree 1000 yard benchrest would be the ideal proving ground, I can't agree what you've shown constitutes proof of concept. That would need a few blind tests.

All true. My first sentence was to address the notion that it can't be seen on a target. Most don't pursue the ultimate results for whatever reason. I dump powder all the time with a measure for various things, but I do weigh every charge for stuff that matters, like 1000 yard Benchrest. Anyone can shoot a small group, but attention to details ensures a repeat performance.

BTW, 1 grain of Varget does weigh .02 grains....

I've shot 1K BR long enough to prove it on paper.....

Not knowing which ammo you were shooting for a given group in a series of say ten groups, with perturbations of one kernel of powder vs. dead nuts?

How about you prove it doesn't matter......

Have you got the ability and equipment?



62 pounds with an 8" forend and 3" butt makes for a pretty good test vehicle....

I won't be weighing to the 1/100 grain, believe me

I'm an Audette developer dude and weigh on an RCBS 750 to the .1 grain if I can keep it zeroed and calibrated


The Audette seems to produce the same results or results that are just as good on the target......



800 yards...




1370 yards....




1610 yards...




1825 yards...

I thought you might go that way with the discussion, but it doesn't really address the question. Make no mistake, I'm not of the belief that since I can't do it then you can't either. I know I don't have the skill and equipment to resolve such a fine detail. To prove it does/doesn't matter requires the equipment and skill you possess. My sticking point is you'd need to run a several blind tests.

Rick,

I agree that it's not always necessary to weigh charges with the utmost scrutiny to get pretty darn good results on LR targets. Here are a few more of mine. These are also all thrown loads. Notice the vertical on the longer targets...

I knew I was going there too......

We agree more than we disagree, but when I'm loading for a match, it doesn't take any longer to weigh to the kernel than not. I use a Sartourios that weighs to the hundredth, but I don't fret over a couple either way.

1K BR is all about the details, so stacking tolerances will not bode well in the end. There may be more than one thing I do that may or may not make a difference, but the expense of testing every one is too costly in a $600 barrel, but costs nothing to do, except a little time.

I've set enough club, state, and world records to prove what I do is not for naught....

1K 10 shot groups can be more telling in your loads....

The other poster did fret over them though, and in a less exacting discipline IIRC. That's what got me started.

I appreciate a good conversation, so thanks.

aalf,

There is no question that 10-shot groups are absolutely more telling than 2,3, or even 5. Having said that, nobody is as picky as the BR guys when it comes to absolute accuracy, and groups that would probably place you in last place, would likely put a big grin on the face of most other shooters, even competitors in other disciplines. You don't need to be able to put 10 shots into groups in the 0.3's to hit a 1.5 MOA steel plate or a deer at 700 yards

For competing, each cartridge should get the utmost attention, but for plinking, mass-produced ammo that shoots 0.5 or better is perfect, at least IMHO.

Excellent shooting, BTW!

Yea, we didn't get too side tracked....

And to summarize (repeat?), it still takes ability, equipment, and desire.....

Usually the definition anal...thanks.

If anyone is interested in a peek inside Litz' mind when it comes to analyzing accuracy and precision of chronograph's you can read here;
http://appliedballisticsllc.com/Articles/ChronographChapter.pdf

I've also read his experiences with the LabRadar and I'll poke around and edit in a link if I can find it again.



Inherent in this statement is an assumption that your LabRadar unit is more accurate than what Litz is using. They claim 0.1% accuracy which makes for 3fps error on a 3000fps capture. Litz' Oehler was similar for precision (though I can't comment on accuracy because his 12ft Oehler was his comparison standard).

Axtell, I'm curious how you conduct your "field testing" to measure your BC's and plot out your drag curves. Is your "field testing" based on your LabRadar? Or are you using an Infinition or other doppler radar system from work? Because here's the thing; the folks at LabRadar told me the best I can hope for in capturing velocities downrange is about 150 yards with a 30 cal if I'm lucky (progressively less as the caliber shrinks). Also they told me I can't put the unit further down range like Bartholome and Litz do with the Oehler on occasion to stretch out the drag curve. They don't work like that. Does that mean you're calculating your BC's using 150yard data and extrapolating beyond to build your drag curves and get your G7 and drop values? Or are you taking drop data and backing it into your computer to give you a BC?

Help me understand as I'm simple and confused.

RCarmuglia,
It's interesting that your friend cited a SD of 8 for a 30 shot string. A long time ago, Bob Jensen who loaded the ammo for the 92 Palma matches cited a sigma 7 as the holy grail for 600 yard loads in my sport (Highpower Rifle). (I'd have to check what N was attached to that). What's interesting is he dumped powder for the 92 Palma Ammo. He shared that he got his sigma 7 through means other than granule accurate powder charging. I think he attributed testing primer lots by shooting primer powered bb's out of a special rig over a chrono to test their consistency and force (he said softer was better). Alan Warner feels otherwise on powder charges. He told me that kernel counting powder charges was the way to consistent elevations at 1K. I think he was trying to rationalize his purchase of his Prometheus. I have a Gen1 and it doesn't make me hold elevation like the Tompkins clan.

Here's Litz' early impressions of the LabRadar;
http://forum.accurateshooter.com/threads/preliminary-labradar-testing.3871199/

What's also worth reading are posts 7 thru 10 of this thread, where he essentially voices what I did above along with a few other things that I didn't think of such as trajectory angle skewing the calculations.

He and 2 others are using a $550 scale that measures to the 1/100 grain. Not sure of the name. They also use a special powder trickler.