caliber accuracy

Conh

Well-Known Member
Hi , after seeing several posts about how accurate certain calibres are (i.e. 6mm br) I would like to ask what makes certain calibres more accurate than others ?
thanks , Connor
 
Lots of factors involved.

Mundane practicalities such as availability of good quality brass and bullets, for example.
Short/fat powder column and small primer flash hole are meant to contribute to more uniform internal ballistics.
Long enough neck to support bullet at appropriate seating depth.

Case designs that rely on head spacing of a rim are often "pooh-poohed" as less accurate (though there are plenty of accurate 7mm Rem Mags, etc.)
 
nope, 6.5-284 is large rifle primer. doesn't have a long neck and a lot of the really accurate loads have loads of space left in the case....

most calibers can be very accurate, if built using good components by a competent builder, then a good load worked up with good components. 6.5-284 is not any more accurate than any of the other full bore calibers.

6mm PPC is easily the most accurate caliber, followed by 22PPC. 6mmBR is also very accurate, as are it's derivative such as 6mm dasher, 6brx etc. etc. 6mm swiss match, 6x47, 6.5x47 are all really easy to get to shoot well.......

lots of different things contribute to accuracy, the caliber is just a part of the equation. it helps to start with something that is normally very accurate though....
 
Mundane practicalities......[that] contribute to more uniform internal ballistics.

Exactly, generally,
Short, fat powder-column
A 30/40 degree shoulder-angle
Generally a long case-neck (which keeps the point where the shoulder angles would intersect if extended within the case neck).
The availability of quality brass (Lapua, RWS orNorma).
The availability of quality bullets (Fowler,Barts, Watson, Carteruccio. Benchrest)

Some examples include 22/6PPC, 6BR Rem, 6.5x47,6.5-284, 6.5x55AI

However, over 90% of accuracy comes from the quality of components surrounding the cartridge, load development
and most of all the NUT behind the gun.
 
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Exactly, generally,
Short, fat powder-column
A 30/40 degree shoulder-angle
Generally a long case-neck (which keeps the point where the shoulder angles would intersect if extended within the case neck).
The availability of quality brass (Lapua, RWS orNorma).
The availability of quality bullets (Fowler,Barts, Watson, Carteruccio. Benchrest)

Some examples include 22/6PPC, 6BR Rem, 6.5x47,6.5-284, 6.5x55AI


+ 1
 
I don't understand why the properties of the cartridge should have any influence at all on accuracy once the bullet has entered the barrel and engaged with the rifling? Surely any variation potentially introduced by the cartridge is entirely negated by the influence of barrel characteristics?

I'm going to hazard a guess that many of these more exotic bench rest cartridges are perceived as more accurate simply because they tend to be fired by extremely meticulous (obsessive?) people using very finely tuned rifles and loads under optimal conditions. Whereas the more mundane, every day cartridges are fired in factory rifles, using factory loads, in less than ideal conditions by people who (often) aren't that bothered about utter precision accuracy.
 
Mungo, competition shooters will use the cartridge that they have the most faith in. They won't or only seldomly use second best.

If one would ask the question of the most accurate cartridge on a German forum one would get different answers than in the UK F-Class scene. Mainly because they
shoot in lower wind areas or indoors 100m mainly 200m 300m to a lesser extent. The 30br is seen to be very accurate there.
Doesn't a 30 cal have the smallest group shot to date? thought I read it on a website.
http://www.accurateshooter.com/cartridge-guides/30br/
edi
 
I don't understand why the properties of the cartridge should have any influence at all on accuracy once the bullet has entered the barrel and engaged with the rifling? Surely any variation potentially introduced by the cartridge is entirely negated by the influence of barrel characteristics?

I'm going to hazard a guess that many of these more exotic bench rest cartridges are perceived as more accurate simply because they tend to be fired by extremely meticulous (obsessive?) people using very finely tuned rifles and loads under optimal conditions. Whereas the more mundane, every day cartridges are fired in factory rifles, using factory loads, in less than ideal conditions by people who (often) aren't that bothered about utter precision accuracy.

You take 2 identicle actions to a rifle builder and get him to rebarrel one in 6mmBR and one in your choice of mainstream calibre with the same make barrel and then go and do some load development, then come back and tell me the 6mmBR didn't pi*s rings around the other one.
 
Cartridges such as the .22 and 6mm PPC and the .22 and 6mmBR have extremely uniform internal ballistics due to what has already been said "an ideal powder column length and width."
Competition shooters then choose such cartridges for their consistant results, however to utilise every last bit of potential from these cartridges the same shooters demand extreme precision built rifles.
A factory built 6mmPPC such as the Sako or Cooper will not be as accurate as a bench rest rifle built by a competent smith, using benchrest chambering techniques.

Ian.
 
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You take 2 identicle actions to a rifle builder and get him to rebarrel one in 6mmBR and one in your choice of mainstream calibre with the same make barrel and then go and do some load development, then come back and tell me the 6mmBR didn't pi*s rings around the other one.

Ok - I'll take your word for it.

But WHY? Why do cartridge characteristics still have any influence on the performance of a bullet that has to travel down 2 feet of metal pipe, firmly engaged with rifling all the way?

I can understand why weight of bullet, speed of bullet and shape of bullet can have an effect, and how these can interact such that two bullets of the same weight but in different shapes or travelling at different speeds (or whatever) can differ in accuracy. And that cartridge characteristics can dictate things like bullet shape, weight and speed. But assuming an identically shaped bullet of the same weight, travelling at the same speed, I would be extremely curious to know how variation in cartridge shape causes variation in accuracy.

I'm not trying to start an argument - I'm genuinely curious.
 
You take 2 identical actions to a rifle builder and get him to rebarrel one in 6mmBR and one in your choice of mainstream calibre with the same make barrel and then go and do some load development, then come back and tell me the 6mmBR didn't pi*s rings around the other one.

You fund it and I'll sit down at a bench next to yours and with a 243 and I doubt we'll find the margin to be that suggested. The point made about quality of rifle build in non factory chambred rifles is not without a certain validity.
 
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Interesting thread.

I've often wondered about the phrase "inherently accurate" being used to describe particular cartridges....
 
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