Some 30 Cal BCs Tested

[Jon A]

Certainly not all-inclusive but I figured some would find the info useful. I measured in about the most accurate way possible for anybody without a million dollar underground range and I'm confident in the results. Of course I wasn't shooting 10 shot strings which would have upped the confidence level (some bullets were more consistent than others) but that'll have to wait until somebody else is buying me barrels. /ubbthreads/images/graemlins/wink.gif Anyway, for what it's worth:

Calibrating the Oehlers:

The 206 yd target/205 yd chronograph, with spotter target to the lower left:

The view:

 

[1doug]

excelent work. Looks like the 210 MK will be one of the new kings of the hill in the 30 cals.

Why 200 yards difference instead of 300 or more? I am gonna be doing the same thing buy at farther ranges @ 500


d-a

 

[Hired Gun]

[ QUOTE ]
Why 200 yards difference instead of 300 or more? I am gonna be doing the same thing buy at farther ranges @ 500


[/ QUOTE ]
No problem. Can we use your chronograph at the 500 yard target?

 

[edge]

Great info, but it makes me wonder why the flip flop of the Sierra B.C.'s

Have you shot the 240 SMK at long range? If so does it hold the same vertical zero as the 210 SMK?

It almost seems as though there may be a stability issue?

Sierra lists the 210 SMK with a B.C. of 0.620
and the 240 SMK with a B.C. of 0.711 ( at your velocities )

Looking at the pictures that you supplied, the ogive of the 210 SMK sure looks like a larger radius to me and therefore should have a better form factor, or am I missing something here?

thanks for the info.

edge.

 

[jmden]

Great work. Thanks for posting. Could you explain how the two types of BC's are arrived at?

Thanks.

 

[remingtonman_25_06]

Ha, just goes to show how over rated barnes BC is. Thats all I wanted to say.

 

[davewilson]

the thing that struck me when the 210 SMK's came out was that they have a secant type ogive. this seems to be a first for sierra. other bullet makers use this style of ogive as it seems to produce a higher BC than a tangent.

thank you very much for posting this. this is the absolute best kind of info long rangers can have, thanks again.

 

[1doug]

[ QUOTE ]
No problem. Can we use your chronograph at the 500 yard target?

[/ QUOTE ]
sure I have a steel outsert so you dont hit any of the skyscreens. You either center the skyscreens or hit the steel gong

d-a

 

[sniper2]

Thank you very much!!!

 

[royinidaho]

Jon A,

That's what I call good stuff. The data is outstanding, your test was out standing and it was w/pleasure that I feel I was able to appreciate the confidence in your work.

I recall how uncomfortable I was at shooting over a 2-bit Chrony @ 200 yds.

The reticle in the scope is the one I dream about. Which scope/model? I'm guessing its an NPR2 ret????

Also what's the deal with the apparent flaw on the Accubond?

Also Ya got me on ICAO????


Again, good work. Very good work.

 

[Jon A]

Thanks guys.

d-a, 200 yds was just more practical. I could get away with testing so many different bullets with only one spotter shot for each before letting three fly at 200, I would have had to be much more careful at a longer range without a shield. I figure 200 is far enough to give accurate data for what the bullets are starting at. And I was pressed for time--that's a lot of walking.... Obviously though the farther you do it the better.

edge, I haven't shot the two side-by-side at the same velocity at distance. That would be interesting though since it looks like they start about the same but the 240 is supposed to remain pretty constant while the 210 is supposed to go down with velocity a fair amount.

At this velocity the 210 clearly has a much, much better form factor which isn't surprizing just looking at the two and the 240 makes up for it with the extra weight/SD. I was really hoping the 240 would measure higher from the 1:9 twist at the higher velocity, but it was within .004 of what I measured it at last year at a slower velocity from a 1:10 twist. Bummer. On the bright side it shows how much room for improvement there is...get a form factor similar to the 210 in a much heavier bullet and it'll blow them both away. Hopefully that will happen soon. /ubbthreads/images/graemlins/laugh.gif

jmden, I used the Quicktarget program that comes with Quickload. You can do the same thing on JBM's Page . I believe those are Metro, divide by 1.018 to get ICAO. I figured I'd list both for the hell of it, hopefully that didn't confuse too many people. /ubbthreads/images/graemlins/laugh.gif They're just two different set of "Standard Conditions" that you should use as in ballistics calculations. ICAO is 29.92 pressure, 59 degrees F, 0% Humidity while Metro is 29.53, 59 degrees and 78%. There isn't much difference, Sierra uses Metro, Nosler uses ICAO, etc. So if you were using Sierra's Infinity program you'd want to use the Metro numbers because that's what it expects you to use....

Roy, that's an IOR 4-14X50 Tactical with the MP-8. The AccuBond had a scratch I didn't notice until I looked at the picture...dropped it on the floor. /ubbthreads/images/graemlins/wink.gif Those weren't the ones I used for the test.

 

[Mikecr]

When you say you calibrated your chrono's, what do you mean?
Is it a comparison between them?
It's a great test. Thanks for the data.
Next time you set things up. Download a few for about 2000fps MV and see how low your BCs end up.

Just for fun

 

[jmden]

Thanks for reminding me... /ubbthreads/images/graemlins/crazy.gif

 

[Eaglet]

Thanks for sharing!!!