shortgrass
Well-Known Member
+1 here! The biggest variable of all!!
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What makes a cartridge accurate?
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Just a viewpoint. For hunting class rifles, including long range rigs, most of the usual suspects can deliver what most would consider very accurate at .25-.5MOA.k sometimes better. I believe it's a function of the total system of components, rifle, barrel, load, etc, and how well they are put together. For this reason someone will always have a case for the "exceptional" accuracy of cartridge X...take your pick. I think cartridge design becomes more relevant when you encounter the benchrest world where the rifles begin to reach an optimized level to the point where the design and construction becomes less differentiated, and the accuracy difference begins to show with the cartridge design. I think there is a reason that certain cartridges have dominated Benchrest competition. They have been proven. The 22PPC, 6BR, 6.5x284, and others are considered to be more accurate, and have produced top scores in countless matches over several years. Shorter and fatter belt less designs seem to contribute to the accuracy factor. Being both a bench shooter and a hunter that has owned and shot numerous cartridges over many years, I became a believer in the accuracy level of many of these Benchrest cartridges. Several years ago I decided that the 6.5x284 had sufficient ballistics to try as a LR hunting cartridge that would meet my needs for 1000 yard medium game. Never looked back. It's really nice to make a confident chest shot on a deer at 1000 yards, but it's great to make a first shot hit on a prairie dog at that distance. The 6.5x284 is no hot rod at 3000FPS and may not have the best barrel life, but if it's all about accuracy, it sure delivers in spades. IMO.
No personal experience but a sharp shoulder (which does not aid feeding), a case that's not to long in relation to the caliber diameter so your powder column doesn't burn to the top irregularly and a case neck that isn't to short so it provides enough, but not to much surface tension for a consistent grip tension on the bullet. I'm not all together sure why a sharp shoulder is suppose to help but it might promote a more uniform burn through the powder column if you mitigate the narrow area at the top of the case. Of course that theory goes to heck on non-compressed loads if the powder is laying on the bottom of the case.
just country
Well-Known Member
Morning, my 2 cents worth of knowledge. between Joe Gibbs and Roy weatherby
there r volumes of knowledge on the design of the sharpness of a cartridge shoulder
from what I have read, experimented , the sharpness of the shoulder of a cartridge
promotes better combustion. the burn of the powder in the case is delayed by the
sharper shoulder. thus we supposedly get better velocity. another + is the
less case stretch. once fired formed to the chamber the cartridge is butted up
both ends of the chamber. the cartridge has much less stretch. very large charges
of powder can change the cartridge dementions .(sp) the experts say that a AI
cartridge, does not give much increase in velocity. I have not used my chrono. to
disprove this statement. I think the barrel length with the design of the cartridge
design make the difference. I have 223AI,243AI, 6mmAI 257AI, 257 Wbee,
340wbee. all shoot very well. I also have 223,243,6mm,250sav. 308 and more in
standard calibers. I do not have a preference as to which is my favorite. fib I
hedge toward my 223AI. stone cold deadly.
this my 2 cents. very good components and A+gunsmith's r a triple A+++++++
just country
life member NRA and TSRA shoot shoot shoot more fungun)
there r volumes of knowledge on the design of the sharpness of a cartridge shoulder
from what I have read, experimented , the sharpness of the shoulder of a cartridge
promotes better combustion. the burn of the powder in the case is delayed by the
sharper shoulder. thus we supposedly get better velocity. another + is the
less case stretch. once fired formed to the chamber the cartridge is butted up
both ends of the chamber. the cartridge has much less stretch. very large charges
of powder can change the cartridge dementions .(sp) the experts say that a AI
cartridge, does not give much increase in velocity. I have not used my chrono. to
disprove this statement. I think the barrel length with the design of the cartridge
design make the difference. I have 223AI,243AI, 6mmAI 257AI, 257 Wbee,
340wbee. all shoot very well. I also have 223,243,6mm,250sav. 308 and more in
standard calibers. I do not have a preference as to which is my favorite. fib I
hedge toward my 223AI. stone cold deadly.
this my 2 cents. very good components and A+gunsmith's r a triple A+++++++
just country
life member NRA and TSRA shoot shoot shoot more fungun)
Seems to me that all other preferences aside, meaning trigger, brake, stock, ect., quality of the barrel and how well it was installed seem to be the driving factor from what I can see. The other stuff just becomes preference and for lack of a better non-existing word, "fitability." This too aids in accuracy. But I guess I look at it this way, if you took the same stock, scope, trigger, and other components, and just swapped out barrels, the main variation would be the barrel, not all the other "fitability" stuff. In the end, does it all come together as one unit working synonymously? Yes. But to answer only the part of the original question, what I believe makes a cartridge accurate, the barrel is the first thing that comes to mind. With that said, all the other stuff is important too, just in a different way. hahaha
What are you trying to say.detect a resemblance
How about the 40 degree shoulder on the Dasher that holds the 600yd record or the 300 Hulk that holds the 1000yd benchrest record or the 35 degree shoulder of the 300wsm that is slowly taking over the 30 caliber magnum stuff used at 1000yds. Believe it or not a 30 degree shoulder is fairly steep compared to many of the calibers used prior to the 6BR and 6ppc. The 222 Remington is only 23 degrees and it was one of the top calibers prior to those. 25-35 degree shoulders are common place for new calibers today but there are still a lot of good calibers with pretty moderate shoulder angles like the 243, 308, 270, 30-06, etc.
Personally I think the barrels are by far the most important part followed by gunsmithing and reloading (obviously the shooter has to be capable as well). Without the first one the rest don't matter. IMO the more the powder capacity increases for a given bore size the harder it is to get consistent result and that is why the most accurate rifles are of relatively moderate powder capacity.
Trickymissfit
Well-Known Member
best place to start in a discussion of an extreme tight grouping cartridge is to read the works of Parker Ackley. Still some more can be learned, but it's a good start. Case volume, and powder burn (nothing to do with burn rates) will make or brake you. You want as much of a complete powder burn as possible. Neck length should be a minimum of 1.25 calibers. Shoulder angle can be all over the place, but there is really only one proven combination. That would be a thirty degree shoulder (in that area), and the longer neck length. The primer can often be important, but the flash hole is just as important. You want an intense stream thru the hole. The longer and hotter the better. Bullets should never be seater with the base extending into the shoulder area.
I used to know Ferris Pindell (one of the PPC designers), and once I asked him about the in's and out's of the PPC design. He was a very candid guy, and gave most of the credit to Lou Palmasano (hope I spelled his name right). Ferris said that the 6BR was a better round past 350 yards. The PPC is what most folks think of as the single most accurate round ever developed, but it wasn't according to Ferris. They had another that was better. It was a 6mm as well, but never saw the case in the flesh. Others I know or knew have seen the case, but I was at the bottom of the pecking order I guess. (he knew I had little interest in bench rest shooting anyway).Ferris said that short fat cases were best, but not to an extreme. Otherwise you had the same problem that too long of a case has only in width. Necks are critical, and tension is even more.
A lot of Hunters Benchrest shooters design their own cases off the PPC ratios, and just expand them to 30 caliber while holding slightly greater volume than a 30-30. Seems to work well for them.
gary
MudRunner2005
Well-Known Member
I'm pretty sure that later on, PO Ackley started using and re-designing all his previously improved calibers with his new 40* shoulder, instead of his initial 30* shoulder that he and Fred Huntington originally came up with... There has to be an obvious reason for that.
Also, if we're talking about proven accurate 1K BR winners, don't forget the infamous .300 Ackley... It is one of my favorite cartridges.
Also, if we're talking about proven accurate 1K BR winners, don't forget the infamous .300 Ackley... It is one of my favorite cartridges.
elkaholic
Well-Known Member
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. Most cartridges can achieve very good accuracy with good components, proper assembly, loads tuned to the rilfe pkg., and most of all, what someone stated, "the nut behind the trigger"!
Having said all that, I do believe that there are designs that give an advantage and make accuracy easier to attain. Also, there are designs that are more efficient, easier on cases, throats, etc. Another factor is "how comfortable is the round for the shooter" which coincides with "the nut behind the trigger". It only stands to reason that if you had two rifles with potentially equal accuracy, but one has 20 ft. lbs. of recoil and the other 50, the one with 20 will very likely put better groups on paper.
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.
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
Having said all that, I do believe that there are designs that give an advantage and make accuracy easier to attain. Also, there are designs that are more efficient, easier on cases, throats, etc. Another factor is "how comfortable is the round for the shooter" which coincides with "the nut behind the trigger". It only stands to reason that if you had two rifles with potentially equal accuracy, but one has 20 ft. lbs. of recoil and the other 50, the one with 20 will very likely put better groups on paper.
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.
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
D
Deleted member 46119
Guest
What makes a cartridge accurate?
What MAKES a cartridge accurate?
What makes a rifle accurate?
What MAKES a rifle accurate?
What makes a shot accurate?
What MAKES a shot accurate?
What do I mean between "makes" and "MAKES"?
Ouch, I hurt my brain.
What MAKES a cartridge accurate?
What makes a rifle accurate?
What MAKES a rifle accurate?
What makes a shot accurate?
What MAKES a shot accurate?
What do I mean between "makes" and "MAKES"?
Ouch, I hurt my brain.
D
Deleted member 46119
Guest
To me to "MAKE" a cartridge accurate means the loader, gunsmith and shooter do all they can with what they have. They try to "MAKE" everything accurate.
To me "make" is the physical characteristics if the cartridge. Those proportions, angles and radius's that "make" the powder burn in a uniform way. That "make" the bullet release in a uniform way. That "make" the chambered round seat in the chamber in a uniform way.
So to "make" a cartridge "accurate" the designer needs to get many things right. There doesn't seem to be a perfect formula for it.
Shoulder angle: There have been superbly accurate cartridges with low shoulder angles but reviewing cartridges perceived to be accurate, a shoulder angle of 30° to 40° seems to prevail.
Neck length: I just can't find any correlation between neck length and accuracy. 300WM, Dasher and a few more are pretty short aspect ratio (diameter to length) much shorter than the diameter of the bullet. On the other side, the 6.5x47L and 6mm Remington are long. Yet all those are known for supreme accuracy.
Case aspect ratio: as in length to shoulder vs diameter. It seems that shorter usually works better. Saying that, again the 300WM, RUM, STW all violate that concept but PPC, BR, WSM, RSAUM, 6.5-47L, Creedmoor all fit the shorter rather than longer idea.
Radius's: Almost every design uses "conventional" shoulder and neck radius. Weatherby used some pretty open radius. Pretty sure conventional contributes to accuracy more than Roy's but there is no formula either way.
To me "make" is the physical characteristics if the cartridge. Those proportions, angles and radius's that "make" the powder burn in a uniform way. That "make" the bullet release in a uniform way. That "make" the chambered round seat in the chamber in a uniform way.
So to "make" a cartridge "accurate" the designer needs to get many things right. There doesn't seem to be a perfect formula for it.
Shoulder angle: There have been superbly accurate cartridges with low shoulder angles but reviewing cartridges perceived to be accurate, a shoulder angle of 30° to 40° seems to prevail.
Neck length: I just can't find any correlation between neck length and accuracy. 300WM, Dasher and a few more are pretty short aspect ratio (diameter to length) much shorter than the diameter of the bullet. On the other side, the 6.5x47L and 6mm Remington are long. Yet all those are known for supreme accuracy.
Case aspect ratio: as in length to shoulder vs diameter. It seems that shorter usually works better. Saying that, again the 300WM, RUM, STW all violate that concept but PPC, BR, WSM, RSAUM, 6.5-47L, Creedmoor all fit the shorter rather than longer idea.
Radius's: Almost every design uses "conventional" shoulder and neck radius. Weatherby used some pretty open radius. Pretty sure conventional contributes to accuracy more than Roy's but there is no formula either way.
