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Alf,
If I understand your post correctly, the theory is that certain case capacity/bore diameters are inherently more accurate than others. If that is correct, since the term "Magnum" can arbitrarily applied be to any cartridge, I don't see where it makes any difference. For example we have the 222 Rem Mag because it has more powder capacity than a 222 Rem but conversely the 458 Win Mag has less powder than the 458Lott.
The theory that certain capacity/bore ratios yield more accuracy I think is proven out by the fact that some cartridges will yield excellent accuracy no matter what powder or bullet weight you feed them. These are the cartridges that are easy to load for like the 8x57 or 375H&H among many others.
I may have misunderstood your post and if I did I apologize but I have always thought there was a certain "sweet spot" in case capacity and/or shape and bore size that would be ideal.

Does it not really depend on your definitions of accuracy, Distance, sights involved and targets ?

Smaller will always be better; that is why bench resters use 6mm PPCs and such instead of 240 Weatherbys.

Here is new BR smallest group shot by 30 cal

http://bulletin.accurateshoote...up-the-gun-and-ammo/

Just my opinion, I am not a benchrest guy.

The fit of the throat to bullet and the neck is very important. Almost any cartridge can be made to shoot very well if the chamber is straight, the throat is close to bullet diameter, and you don't have excessive freebore. These are often neglected points.

Many SAAMI spec chambers are a trainwreck in this respect. Many manufacturers do stupid stuff, like using a drill press to spin a chamber reamer. IMHO if you load a straight cartridge, shoot in in a decent chamber, with a well designed throat, it is downhill from there. Yes you need decent bullets too. IF however you have a rifle with a sloppy chamber/throat no amount of load development is going to get sub MOA accuracy.

For a hunting/ varmint rife , there is no magic in a particular cartridge, IMHO. If you want to shoot shoot groups in the teens or better that is a whole other ball game.

That is a very good question. It would depend on the case volume vs the charge/bullet weight.
In your above post,with all due respect to the original author who is no longer with us, I do not agree at all about the anti-tank gun chamber barrel pressure. However,I will not bog down your question.....
A magnum primer with a "heavy charge and medium to heavy bullet is very capable of sub-MOA accuracy.
Where the "Magnum" primer causes inaccuracy is when you have a powder that needs a little more time to ignite is blown forward by the primer and dislodges the bullet and starts to engage the origin of the rifling. This force is not consistent from shot to shot as HOW the bullet enters the rifling is extremely important. If the bullet has yawed even the slightest amount, accuracy will be adversely affected.
If the powder is faster burning it can in fact help powder burn. A magnum primer used with SOME powders can be equal to a whole grain extra of powder. Depending what load is used, this could cause the bullet to travel too fast for the best accuracy or cause a pressure spike.
Years ago CCI did an outstanding article on primers and their effect on the powder charge.
Did you know most Bench Rest primers are almost identical to a Magnum primer? They what the brissance and flame temperature will uniformly ignite the powder charge.
Since this article was written I have loaded thousands and thousands of rounds using magnum primers. With the right powder type and bullet weight I personally have achieved impressive accuracy out to 600 yards (documented.)
The above article proved what Dr.Mann's research in his book "A bullets Flight" proved time and time again. A Heavy,slow bullet will display outstanding accuracy at long range.
Think Creedmore Matches shooting the old Black Powder Metallic Cartridges firing heavy lead bullets at 1,000 plus yards, shot very impressive scores.
The primers used in those days shot a flame out of the barrel by FEET and had too or they would not be accepted.
I have been involved in exterior ballistics my whole working life (45 years now) and still do to this day.
What happens within the few milliseconds of you pulling the trigger until the bullet leaves the barrel is very interesting and eye opening as well. I have spent countless hours taking ultra high speed X-ray films of what just goes on during this time. I could bore you to tears on facts & figures on what takes place.

Accuracy in absolute terms has so many interdependent variables involved that it is hard to quantify an exact element.

But overall I think it is proved out that the standard rounds have more accuracy at modest distances. A quick look at the the winning bench rest calibers over the past 25 or 50 years should convince most of us of a similar overall concept.

But when you break it down to all its elements and the interaction of them, much less by a particular application and on a particular day, by a particular shooter in a given set of environmental conditions, now you can get subsets of non unique answers.

From the magnum perspective accuracy doesn't mean too much if the bullet can't arrive on target . So there should be a point, or a range of points and values, where the magnum starts improving in accuracy and the standard round starts decreasing in accuracy. But these may be seen in relative terms .

I think if you normalize all the terms at relatively short distances and look at the meat of the distributions then the standard caliber will win more .

But eventually the magnum has to have its day. However short and at what ranges that might be. Then we reach a range where accuracy degenerates, and then a range where it becomes meaningless for a practical application by the original definition we gave to accuracy or comparable accuracy.

Finally there is this whole how much is enough, and enough is never enough circle too. Take a 1860s artillery engineer or officer and a 2014 artillery engineer or officer and compare that to a cruise missile .

But overall arent we glad we have different tools for different applications.

Thanks for that link: There are many other factors that have greater impact than piezometric efficiency at hunting ranges.
Powder variables and fit of bullet to throat must surely be the biggest.
Also interesting to note a 1:17" twist Krieger barrel was found to be optimum for a pointy, 114-grain, 30-cal bullet,
at 2980 fps from this relatively small cartridge case.
Pretty "stout" load as the record setter said.

Slow twist ought to add to piezometric efficiency too, in the quest for diminishing returns.

quote:

Originally posted by tom holland:
Here is new BR smallest group shot by 30 cal

http://bulletin.accurateshoote...up-the-gun-and-ammo/

0.0077" Five-Shot, 30-Caliber, 100-Yard Record Group:

About the Cartridge — 30 Stewart (Based on Lapua 6.5 Grendel Parent Brass)

Mike explains: “Our goal was to shoot H4198 as the optimal powder for stability.
Temperature stability?
There were several versions of the reamer before we settled on the current configuration. I am optimized for the 10 Ogive BIB bullet,
powder to the base of the bullet. I found in testing the small 30-cal case did not like compression at all. The bullet is seated only 0.12″ into the case with zero freebore.

This cartridge has ALF's piezometric efficiency, and a lot more going for it.

Cases were initially created with the .220 Russian (like a PPC) but I later decided it was better to build from the 6.5 Grendel. I size the brass and bump the shoulder back until it will fit into the chamber, fill to shoulder with International Clays, cotton wad packed on top. I have a fire-forming barrel. (I would not recommend this Clays and cotton wad method in a good barrel.) After initial fire-forming, I then mandrel the neck up the rest of the way to .30 caliber, turn the necks and trim.

It takes at least 8 firings to fully form a case!


If you fire only three loads I find the brass does not have a sharp shoulder or any pressure on the bolt so any die selection is incorrect.
Brass continues to harden well past 25 firings.



I have match brass with well over 500 rounds fired, and I have never blown a case or neck yet (using my forming method).



For loading I use a Hornady Custom Shop Sizing Die


and a Ralph Stewart Custom Seating Die. For those who are curious, yes the small group was fired with pre-loaded rounds. I do this now and then with local matches or may load 50 in a batch for one match."

I was musing the other day at the notion that most of the time when you see "most accurate load" published in reloading manuals that the majority of them tend to gravitate towards the upper end of the maximum load spectrum and how that might relate to inherent accuracy questions among Magnum vs standard calibers. This upper end of efficency for best accuracy phenomenon has been my experience with reloading as well for the most part. Although Ive not done any significant comparison to qualify that thought.

If I were a betting man and two rifles to choose from were a 7mm RM and a .30 carbine I certianly wouldnt take the lower piezometric version in that accuracy contest. But for the most part I agree with TexKD, lots of variables makes for apples and oranges. I think that to simply hand the trophy to standard rounds as they are what are seen more among the benchrest fraternity is a lacking assessment though, because I am sure there is a strong element of practicality involved in such choices. In comparison, the use of high intensity Sniper rifles seems to be a growing trend thesedays. But again, I believe that practical purposes trumps 1/8" MOA better accuracy potential here.

Intresting about the howitzer theory though. It seems to me that if this artillary theory and design principle applies to small arms, then one could reasonably expect better accuracy potential from a snappier/faster powder burn rate as opposed to a slower one.

I think this subject would need a lot of definitions to keep any discussion and comparisons valid.
High angle artillery such as a howitzer is known to be accurate as defined by putting repeat rounds on a target by indirect fire.
Hunting rifles are rarely tested like that because they are direct fire weapons similar to tank and anti-tank guns.
At one time infantry rifles were considered for long range volley fire but I think that was last used in WWI.

I suspect the Germans already know the answer to the question from their use of the various 88mm tank guns, 88mm tank destroyer guns and the 88mm dual purpose gun.
The 88mm dual purpose gun was used as anti-tank, high angle antiaircraft and as direct fire artillery. I have not read if it was also used as long range indirect fire artillery. I am sure that in developing ammo and firing techniques for these and similar German weapons they would know the answer.

"Many SAAMI spec chambers are a trainwreck in this respect. Many manufacturers do stupid stuff, like using a drill press to spin a chamber reamer."


That's an interesting statement. I'd like to know 2-3 of those "many" stupid drill press chamber reaming manufactors. ??

There is a an old photo of a SAVAGE "factory" tour in a 1970s Rifle or Handloader.

They have a an old floor model 15" inch drill press with the table swung aside. On the base of the drill press they set a metal trash.

I assume they had center mounted to the base of the drill press for the barrel muzzle.
The woman operator had about a dozen barrels standing in the trash can. There was a chambering reamer in the spindle and the woman was picking up the next barrel to ream.

Believe it or not....

quote:

Originally posted by Jim C. <><:
That's an interesting statement. I'd like to know 2-3 of those "many" stupid drill press chamber reaming manufactors. ??

Considering that 2000 m was beyond reach of most other tank and anti-tank weapons a 50% hit rate is still pretty lethal when you do not have much risk from return fire.

quote:

It was capable of good penetration capability up to and beyond 2000 m but the chance of actually hitting the target at 2000 m was not very good. no more than 50%.