What makes a cartridge accurate?

[HARPERC]

.......I think for most us, we like to balance what kind of velocity we want, what distance we are shooting, what is the intended target, etc.........

The parameters/rules of the game we choose to play, will usually decide what works best most of the time.

Occasionally someone comes along whose abilities are so much better than the crowd, those wishing to improve, shamelessly copy everything they can.

So many variables involved, I'm not certain the question can be answered.

 

[Greyfox]

I only read thru the first 3 pages of this thread, but for the most part, i agree with much of what has been stated.,,,,,,,,.....................................
My personal preference in the cartridges that I have designed attempts to incorporate many of the above mentioned. I like velocity, but not at the expense of having to swap barrels every 1000 rounds or less. I like minimal body taper and a sharp shoulder to reduce case stretching and prolong case life. I like a neck long enough to adequately support long bullets which I believe makes accuracy easier to attain. A longer neck, in conjunction with a sharp shoulder, also keeps the flame point directed more inside the case neck, rather than directly into the throat. This increases throat life, and in turn, keeps the rifle accurate longer. In the case of my SS design, I believe that the very short powder column significantly increases performance over equal capacity long cases. I also believe that "the potential" for accuracy increases because ignition is more consistent. The bottom line is that no one thing, or even combination of things, guarantees an accurate cartridge, but there are certainly ADVANTAGES in a design. My two cents......Rich

I agree with the principles of the short, fat case, and sharp shoulder contributing to accuracy. I'm curious about the concept of flame point. It certainly seems to make sense that a flame point directed inside the neck as opposed to the throat would give less erosion of the throat and therefor greater barrel life. I'm interested in how flame point location is actually determined. Is it empirically determined, or speculated based on observation? Does powder volume, burn rate, pressure, or any other variables besides case design effect the location of the flame point for a given case design?

 

[tbrice23]

I wonder if Roy Weatherby was thinking about flame point on his double radius (venturi) design? Giving added turbulence to the flame point, but seems moot because no one seems to think his designs are the most accurate cartridges.

 

[elkaholic]

I agree with the principles of the short, fat case, and sharp shoulder contributing to accuracy. I'm curious about the concept of flame point. It certainly seems to make sense that a flame point directed inside the neck as opposed to the throat would give less erosion of the throat and therefor greater barrel life. I'm interested in how flame point location is actually determined. Is it empirically determined, or speculated based on observation? Does powder volume, burn rate, pressure, or any other variables besides case design effect the location of the flame point for a given case design?

I do not have any true formulas, etc., which determine flame point impact on throat erosion, but have had it explained to me this way: If you use a cutting torch as an example, when you adjust the flame point using the oxygen, the hottest point is right at the tip of that convergence. The shoulder angle of the case theoretically "funnels" the hottest gases to a point where this angle converges as well. If you imagine lines drawn directly down this angle, the sharper the shoulder, and the longer the neck, the farther back inside the case mouth this flame point is. This has seemed to bear out in the 6.5 Sherman so far. An example of a case that has a short neck with less than the Sherman shoulder angle is the 6.5/284 which is not known for good barrel life even though it has considerably less capacity than the sherman.
There are powders that burn at different temps and it is widely accepted that pressure is also a factor. Whether or not these variables affect the location of the flame point, I do not know? This topic would make a great research project for someone with the equipment and know how to do it. I would think that the military would have data concerning this?.....Rich