Yes, there will be variation, no two bullets will have exactly the same BC if you take it out to enough decimal points, etc....
But I think it's important we not get lost in the minutia here. I've seen some bring up all these variables before as evidence that BC's are pure bunk, hokus pokus and aren't worth worrying about at all. A typical case of being afraid to identify a forest because he's afraid he won't be able to count every tree.
Yes, there will be variation. A standard deviation is always a good thing to report with any testing. And different rifles, different twists, environmental conditions....
But! It is possible to judge the relative size of different forests without counting each tree in each forest with absolute certainty.
I hate it when people see instrumented tests on BC's and say, "Yeah, well maybe in your rifle the round noses don't beat the SST's but they might in mine.... Maybe under your conditions a high SD sharply pointed bullet kills a light, low SD X-bullet...but in my rifle they might not...they might be "magic!"
Sorry, just ranting. That wasn't aimed at anybody in particular...just a direction I've seen arguements like this go before. Yes, BC's change, vary and are dynamic. But let's keep those variations in the proper perspective.
I don't know that all ballistic software utilizes a "corrected BC" in calculation of time of flight, etc.
I know some do.
I'm thinking many trust your BC input and calculate velocity retard based on drag rather than a variable BC.
Your real BC(not published at ICAO or StdMetro) is effected by your mach number. And this has a marginally opposite relationship with air density to drag. For instance, a bullet with a .553BC, 3Kfps, ICAO, has a BC of .549 at 90deg. Notice BC dropped at higher temp. This is not "corrected" BC, but real -local BC. External ballistic programs would calculate from there, using this real BC in a number of ways(whatever method chosen).
An example can be seen using JBM's website calcs(like Drag/twist calc).
I don't know. Maybe I got it all screwy. It just seems weird to take a measured local BC to a different standard.
Maybe because I don't get alot of woodchucks at sea level and 59 degrees.
That is a hell of an idea and am sure Richard will go for that. He frequents this board so he will see it.
As Kirby said and you. Richard wants to make his customers happy and will do about anything you want, in reason.
Hell Daivd Tubb went to Sierra and told them the bullet he wanted them to make and was told NO!! So he found another makere to make the bullets and is selling a crap load. Can't keep stock fast enough. TO bad for sierra.
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Ummmm, Sierra makes Tubb's bullets [img]/ubbthreads/images/graemlins/crazy.gif[/img]
I suggested a 110gr 6mm ULD/RBBT
you and me both [img]/ubbthreads/images/graemlins/laugh.gif[/img]
I agree with you on your point, however, for purposes of actually shooting a projectile at an intended target, standardized bc and affected bc show no distinction to the shooter. Affected bc does change with all the "other" factors that are not topologistic, and these are the bc's that a shooter in the field sees. Realizing that most of the people reading this thread would rather go shooting than do math homework at a desk, I lumped both affected and standardized bc's into one for the ease of explanation to the shooter.
After briefing the 5 pages of posts, I am amazed at the knowledge and sometimes petty pickering that can come from that knowledge. Glad to see it 'smoothing' out.
I think we can agree that ANY BC figure is merely that, a number. The real world performance will be different for us all. That performance will change from day to day, location to location.
Hell, our scopes don't adjust the same and our rangefinders have error. They may be consistent but they have error never the less.
Bottom line is how do these bullets shoot in the one thing that does matter - small groups. Are these bullets consistently accurate at the ranges and velocities that matter to you and only you? If so, then they are a success and a bullet worth purchasing.
Matt27, I am glad to finally hear that you tested the 140gr SST and did show reduced elevation adjustments as compared to the Lapua's. If someone ran those numbers for comparison, they would get a reading higher then the Lapua's 0.65. Are we both nuts? NOPE.
Why haven't others tried them and posted their results? Mostly, because a hunting bullet 'can't' fly that well.
Before everyone jumps on a bandwagon, they might want to do some personal testing to verify. Your mileage may vary but you will see trends that matter.
Too often, this sport is driven by the written 'facts'. Very little actual shooting going on. And the testing that is reported is far from statistically correct. 2 5 rd groups to determine the fate of some product...BUNK. Especially when you see a pic of the author/tester using a rolled up blanket for a front rest (true, just look at some of the 'established' gun mags) or a 16" bipod and no rear rest.
Funny since we don't judge race cars by how they look in a parking lot.
Let's all get out there and burn powder. We will then be able to come to some real world conclusions about how things do or don't work.
Richard is a guy trying to make a good bullet. FACT. Let's leave it at that and just shoot them. If you like them, great. If you don't, great.
The real world BC values will come to the surface fast enough. I doubt two of us will agree on a number anyways...