Quantifying inherent accuracy ?

[pemo]

Hi there,

Has there been any attempt to quantify inherent accuracy similar to the overbore table attempting to quantify barrel life here:

http://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/

Or do you consider "inherent accuracy" a myth ?

 

[Mozella]

Interesting question. The article touched briefly on "inherent accuracy" and I find it interesting that the .223 Rem and 6MM BR are right next to each other on the chart. In my experience, those two cartridges are quite different when it comes to natural born accuracy. I shoot 600 yard competitive matches with both calibers. I treat both guns and both kinds of ammo with equal care other than I have a LOT more development work invested in the .223.

If there is such a thing as "inherent accuracy" I would suggest that the 6mm BR has it over the .223 Rem by a significant margin. Not only is my best 6mm consistently better than my best .223 at long and short ranges, it was a good deal easier finding the best recipe with the 6mm.

I don't know why and I'm not prepared to worry too much about the reasons, but I have a strong feeling that what I see is true and not just some anomaly. It may or may not have something to do with the formula used in the article you reference, but I'm pretty sure there's something to "inherent accuracy".

 

[Sniper338]

Interestig thought. There ia definently calibers that are naturaly more accurate.. im a firm beleiver in that!

 

[gunsandgunsmithing]

Hi there,

Has there been any attempt to quantify inherent accuracy similar to the overbore table attempting to quantify barrel life here:

http://www.accurateshooter.com/technical-articles/overbore-cartridges-defined-by-formula/

Or do you consider "inherent accuracy" a myth ?

Certainly a who's who of some of the most accurate cartridges ever developed in the top 14 of that list. I'm a believer...there's more than coincidence to at least 12 of the 14, all of which are proven winners. If it were on the list, and using that same formula, a 30 Major(Grendel) would be at the top. It just happens to hold the 5 shot 100 yard world record.

 

[Berger.Fan222]

My pet theory is that lower capacity cartridges are more accurate for several reasons:

1. More of the energy of higher capacity cartridges goes into setting the action and barrel in motion before the bullet leaves the barrel. Less motion is more accurate. For equal accuracy, you probably need to scale up the mass/stiffness/rigidity of the barrel and action with the weight of the powder charge. In a given weight rifle, less powder will be more accurate.

2. Lower capacity cartridges will have lower barrel pressure kicking the base of the bullet when it leaves the barrel.

3. Lower recoil means less rifle displacement before the bullet leaves. It also means less flinching.

4. Lower powder charge means less muzzle blast - less psychological reaction (flinching).

So, its a combination of physical and psychological effects, but they all work in the same direction.

 

[mac86951]

I'd say inherent accuracy is a loose term. I've never seen a benchrest rifle chambered in 7.62x39, thus is this cartridge inaccurate? It does have similar background to PPC...

I see it more of a difference of purpose. You'll never find an AK chambered in a turn neck 6PPC, nor a benchrest rifle in 458 Lott. Both certainly serve a purpose.

The overlap cartridges are tough. I've seen 223 accurate, and I've seen 5.56 barely hit a barn. Tolerances are to blame in the diversity, but again to what purpose.

I'd have to partially agree with capacity and instead look at efficiency. List them by efficiency and given equal rifles you'll probably have a realistic inherent accuracy.

Barrel life needs to be considered too, I'm sure the 17/50bmg could put three shots in one hole but that would be about the end of the barrel too...

-Mac

 

[chkunz]

Here is a hint, cartridges with smaller head diameters are more inherently accurate than those with larger head diameters.

 

[mac86951]

Here is a hint, cartridges with smaller head diameters are more inherently accurate than those with larger head diameters.

Hmm, this brings the next question, at what distance? I'm guessing we are measuring equivalence at 100y. Perhaps you're right, but should that distance change im sure the answer would too.

 

[chkunz]

Hmm, this brings the next question, at what distance? I'm guessing we are measuring equivalence at 100y. Perhaps you're right, but should that distance change im sure the answer would too.

The rules of this game have not been defined: distance, barrel life, etc. have been mentioned. I just jumped in with a first order consideration. By the time the replies get to 10 we will be hopelessly down the rabbit hole.

 

[Mozella]

Here is a hint, cartridges with smaller head diameters are more inherently accurate than those with larger head diameters.

How many people would shoot .223 in F/TR if they suddenly allowed 6mm BR in the F/TR class? Answer, not too many. I'm not convinced that case diameter is the predominant factor in "inherent accuracy".

 

[pemo]

I ask because it is farly obvious that some calibers have higher potential compared to others. My understanding is that increased recoil is not helping precision but is not included in the term Inherent Accuracy (IA) eg. a 308Win has a fair bit of recoil but is still considered born accurate.

So is IA more or less relating to case design only, perhaps in combination with forgivingness to eg. minor case volume changes and bullet hold ?

 

[gunsandgunsmithing]

Efficiency is relative to case capacity to bore ratio. More efficient cases allow for faster, more efficient powders, that do the same or more work in less time than slower powders. This yields at least the benefits of lower muzzle pressure and slightly less recoil. Theres obviously more to IA than just cartridge efficiency, but I believe it's a large and repeatable factor.

 

[ireload2]

A good part of that list consists of cartridges that are not chambered in truckload of cheap mass produced rifles with indifferent to crummy chambers.

 

[dcali]

Here is a hint, cartridges with smaller head diameters are more inherently accurate than those with larger head diameters.

I think there's a lot to this - up to a point. When you start to get very long cartridges, I start to wonder about combustion efficiency/consistency, and mechanical tolerance issues. Imagine a .223 casehead as long as a .30-'06, for example. Low bolt thrust, high velocity, but at what cost?

The 6.5-'06 seems to have fallen out of favor relative to the 6.5x284. I've never understood why, although I don't have any experience with either.

 

[dcali]

How many people would shoot .223 in F/TR if they suddenly allowed 6mm BR in the F/TR class? Answer, not too many. I'm not convinced that case diameter is the predominant factor in "inherent accuracy".

That's a matter of ballistics, not accuracy.

I think case diameter is *a* factor. Smaller cases have less bolt thrust. Less bolt thrust means less force to drive the barrel vibration, which should lead to better accuracy. But it's just one factor. I believe (without any real evidence - just speculation) that this is the main reason the 6 PPC edges out the 6BR.

 

[chkunz]

That's a matter of ballistics, not accuracy.

I think case diameter is *a* factor. Smaller cases have less bolt thrust. Less bolt thrust means less force to drive the barrel vibration, which should lead to better accuracy. But it's just one factor. I believe (without any real evidence - just speculation) that this is the main reason the 6 PPC edges out the 6BR.

Also, the smaller case head is more forgiving for asymmetrical force on the bolt face.

 

[Ggmac]

I'm not sure about the bolt thrust , here's why . The longer case , say 30/06 or 30/30 has more case area , hence lower bolt thrust than a similar short fat case of equal volume . The pPC has the same case cap as a 6 TCU or 6-45 but the short fat case has been proven to be more accurate .
Bill Calfee did a complete test and good article on it .
Anyway , that's my take . I think cartridges are more efficient which may translate to more accuracy

 

[Brians356]

The pPC has the same case cap as a 6 TCU or 6-45 but the short fat case has been proven to be more accurate.

"Proven" more accurate? Mathematically proven? Uh, no. There's no way to prove a cartridge or cartridge family is more accurate, there are too many variables, and too many chaotic perturbations. It's a multivariate chaotic system.

Besides, doesn't the 222 Rem still hold a significant benchrest record?
-

 

[Ggmac]

Sorry , as close as possible , read his testing , very good reading before you nix the proven concept . Same barrel same receiver same bullets etc all done by a proven riflesmith .
No to the 222 , not since the pPC

 

[Brians356]

Sorry , as close as possible , read his testing , very good reading before you nix the proven concept . Same barrel same receiver same bullets etc all done by a proven riflesmith .

"Strongly suggested most accurate."

No to the 222 , not since the pPC

Are you sure? I believe there's still one particular record held by the 222 Rem, one of those flukes unlikely to ever be bested. I believe it is a ten-shot group. Guys, help me out here, I am not a competitor or BR historian.
-