GG I understand that but if you also look at Kirbys targets at 500 yards With a couple different cals he has shown on here it is hard to argue that Wildcat bullets are not accurate. I know you had a 40 shot group and I am not saying your rifle is not a shooter because believe me I think it is really impressive and anytime you want someone else to test it for you just let me know. [img]/ubbthreads/images/graemlins/grin.gif[/img] But what some on here do not understand is the bullets Kirby has been shooting are big game bullets not target bullets. They are not desinged to shoot paper they are designed to take a impact at 50 yards and still open up way the hell out there. To me that is very impressive. I know Sierra bullets can shoot I shoot a lot of them but they dont make a bullet in the cals I shoot that can take a beating at 50 yards and still open at 1000 yards. About the only thing that comes close is the 300 grain Matchking for a 338. As for my Wildcat bullets I have some 7mm 175 grain ULD point flatbase which will have a bc around the .700 mark. Even if the bc only turns out to be .600 I would still be happy if they shoot well. I also think a bullets published bc is just a guide kinda like a reloading manual. Every rifle is different and bc can be change with so many Variables. I think when one wants to find a bullets bc you have to do it rifle to rifle.
Someone mentioned that I quote JLK BCs and then question Wildcat BCs...
I don't quote anything from Jimmy Knox - my numbers have been verified by chrono to 600 yards at around 800 ft ASL and via drops to 1000 in western MO and to 2000 somewhere in central South Dakota. Then Brent and others verified with similar numbers (Brent has an Oehler, I don't remember what everyone else over the last few years has used) in their respective locations...
STL. Principal Consultant and Managing Partner - Association of Bifurcated Tangential Ballistic Apologists, LLP.
Hopefully the applied mathematician in me won’t BIG TIME bore everyone to tears. I’m sure we are all aware that BC is dynamic, not a single number, ie it depends on Velocity.
When folks talk about using <font color="red"> a <font color="black">chronograph to get the BC, I hope they mean using <font color="red"> a PAIR <font color="black">of chronographs unless they are doing the correct statistics (which means you would need a lot of measurements too unless you have an exceptionally low StdDev in velocity). I believe Doppler radar is the preferred method to accurately get BC.
[ QUOTE ]
Everything and anything affects this number. These are just a few bc tweekers:
[/ QUOTE ] <font color="black">
Actually, the only things that effect BC are physical, ie topology (shape, defects) . axial symmetry, density and velocity. the new list
<ul type="square">[*]barrel condition[*]bullet bearing surface[*]bullet meplats[*]bullet dings/scratches[*]Weight of individual bullet[/list]
The following factors only change effective BC, not actual standardized BC. IE, these are environmental factors that effect bullet flight but have impact on corrected BC – ie if you corrected for these factors, then tested the bullets at Std Temp, pressure, Humidity, (I believe Altitude can be rolled into pressure), wind vector – you would get the same BC value. If you moved to another pressure/temp/humidity location you would still get the same BC.
Twist can also be corrected for sans sub stabilization. If you know the true BC, ballistics can accurately calculate the Velocity, [de]Acceleration, position at any position or point in time - pre subsonic. Precipitation could be corrected for but it would probably be too difficult to accurately quantify rain/ice conditions.
Properties that effect perceived BC but not actual Standardized BC
<ul type="square">[*]Humidity[*]barometric pressure[*]air density/altitude[*]temperature[*]wind direction[*]wind speed[/list] [ QUOTE ]
There can never be two bullets in the same box with exactly the same bc.
[/ QUOTE ] <font color="black">
Perhaps if you want to get into quantum physics but given a large enough batch you could find identical BC bullets <font color="red"> within the bounds of your measuring tolerance <font color="black">
That is where Standard Deviation comes in. If you know the Std Dev of a batch, you know expected variation. If you further add extreme spread, you know everything.
I’m not flaming or picking on you goodGrouper – I respect the awesome work/shooting/experience/info you bring to this forum. I hope to some day get 90% of the results you are getting today.
Kirby don't take offence, you know I'm your #1 Fan.
Drop charts are fine in you're always hunting at the same elevation/temp - But I'm using my 300 RUM (until you ship me my Kirby/Lilja 300 RUM [img]/ubbthreads/images/graemlins/smile.gif[/img] ) for yotes outside Bakersfield CA - hot & low altitude. Then I'll be using it for deer along the Missouri Breaks next fall ( 3,500 ft ) then moving to my cabin near showdown ski resort ( 7,400 ', cold ) - yotes/rabbits in goodGrouper s stomping grounds (santaquin UT ) - then on to the Nevada dessert.
I can't do a drop chart at each location, but once I <font color="red"> Calibrate </font> a ballistics model, I can move to any of these locations and very accurately compute drop.
If you want to use drop to approximate BC you can get more accurate results if your scope is exactly parallel with the bore.
A couple problems with using the drop approach is you need to know the Std Dev of velocity spread and BC to compute a BC #. IE, if bullet 1 has a BC of .700 and #2 has a BC of .710, then you get an inflated BC approximation. So you really need to know both Vel and BC to compute BC. This can actually be done by estimating the BC and using some statistics.
Getting the Velocity at two positions from one bullet gives you ZERO variation in BC and Velocity.
Wind, pressure, temp variation are also minimized.
I suppose you could do some non-trivial statistics to correct for these variations and use only the drop approach, but depending on the consistency of your groups this could involve many test shots. I need to think about how you would correct for two significant variables (vel & BC) – You see the problem, bullet 2 has higher Vel but lower BC, bullet 3 has lower Vel but higher BC.
As my other hero goodGrouper eloquently pointed out BC changes from bullet to bullet, minute to minute. ( I think he left out barrel temp )