b.c accuracy

[strud34]

Hi was looking at some light 6mm varmint bullets and the B.C on some don't look right how accurate is the clams of the manufacture?

Was looking at the nosler 55gr with a b.c of 276 and then look at the 58rg vmax b.c 250. The vmax has a bigger boat tail and is 3 gr heaver than the nosler and just looks more streamlined but the nosler has a much higher b.c.
Even the 65gr vmax only just has a better b.c 280 with all that extra wight.
the burger 65 gr Match BT Target b.c 270 .
so why it the nosler got such a high b.c for its wight?

 

[KevinThomas]

Big can of worms here. If the manufacturer in question actually did the time of flight firings (not all do), then yes, they're spot on accurate. However, they're accurate for that distance, at that location, at that velocity, etc.. First thing to understand about BCs is that they're variable, and testing a bullet under different circumstances (or at a different distance) will almost always yeild a different value. BC isn't like length, diameter or weight; it's not a hard and fast number, and there's a range of variables involved in measuring it.

Use the numbers given by the manufacturer. If you ever get the urge to measure it for yourself, and are willing to jump through the appropriate hoops to do it correctly, you can do your own. Educational, at the very least, and may well yield numbers that are more useful to you in your particular situation.

 

[serial # 001]

Kevin Thomas,

If it was a hot day when Nosler shot theirs itwould show a higher B.C.

 

[KevinThomas]

Serial #001,

Atmospherics definately make a difference, but they should be corrected back to "standard." This way, we're all on the same playbook, and the comparisons between one BC and another shot at a different time/place/condition should be valid. In all of our TOF studies, Bill McDonald needed altitude, barometric pressure, temp and humidity for the correction factors, which result in the BC figures given in the Sierra manuals. I'm sure Nosler, Hornady and Speer do exactly the same in their BC firings, as this is pretty much industry standard. In this manner, the variables caused by such atmospherics are effectively cancelled.

 

[strud34]

right so they should be right on with the b.c and would of calculated all the differences in atmospheric conditions. So one manufacture b.c will relate to another is that right

 

[mikecr]

The problem with BC listings is that they aren't qualified to any standard.
This, as in .xxx G1 BC @ 3000fps, ICAO adjusted.
There are multiple atmospheric standards(StdArmy, StdMetro, ICAO), and velocity(actually mach#) plays a big role, affecting BC reporting.
Berger has adjusted their reporting to represent a best average downrange(I like) ,and also providing G7 BCs(I like again).

You will have to validate local BC, or research to find a better source(like 'Applied Ballistics' from Bryan Litz).

 

[KevinThomas]

Strud34,

Yes, that's correct. However, the observed BC at your location will likely be a bit different, sometime dramatically so, depending on what you're doing. Mike mentioned another variable, but most in the industry have used ICAO atmospherics for some time now. But it pays to verify, since as he implies, it's not a sure thing. Pays to ask, and make sure. Most should be happy to tell you, if you can track down the right person.

As far as a BC being "right on", again, yes, but only for those conditions, at that range. Differing ranges will account for wildly different BC results, regardless of the drag model used or other standards applied. In other words, if the BC was derived from 200 yard TOF firings, shooting it at 1000 yards will give (sometimes vastly) different results. Bryan does most or all of his shooting at full distance, so when he (Berger) gives a BC, you can be fairly certain it'll match up closely with what you'll see in the field at like distances. Clear it up a bit?

 

[strud34]

KevinThomas
thanks
so they should be accurate but thers always a but :.
I think im about there
thanks for the time

 

[floydj]

Berger has good and simplified answers in their FAQ's that may clear up your question. Some bullet companies may base their BC's on a computer model only, I would be suprised if this is how Nosler operates but they may be basing their numbers on science theory rather than science fact.

 

[strud34]

it still seems to high, b.c .276 for a 6mm 55gr nosler
just look at a burger 65 gr Match BT Target b.c 270 .
65gr v-max b.c 280
both 10gr heaver.
it just don't seem to add up. but i guess i will take it as right with out testing for my self