[Rich Z]

You know, I've heard this off and on over the years, where someone will say that one particular cartidge is "inherently" more accurate than another. But is there any truth in the matter?

Are there any cartridges that tend to produce more consistently tighter groups than other cartridges? If so, what is the magic formula that would make them more accurate than a not-so accurate round?

On the other end of the scale, are there some cartridges that are inherently troublesome to get good results from?

 

[anodes]

RichZ, This topic has been a concern of mine for some time. And it can piss me off @ the answers I get when asking the same question! Fer instance: "Well, it will only be as accurate as the shooter.", like I DIDN'T know that! There was some feedback on this in a recent G&A Letters column regarding the long proposed assertion that the .222Rem was more "inherently accurate" that the .223Rem, two VERY similarly designed cases. The response was, "We asked C.Boddington and he said, 'Shooters who have shot both will tell you the .222Rem is the more accurate cartidge.". Isn't that great? It's more "inherently accurate" because C.Bod. said 'others will tell you so'! They didn't address the writers specific questions as to WHAT make one more so than another, just validated thier claims with more inuendo and hearsay! Now if they had gone on about "a shorter powder column gives a more consistance burn pressure from shot to shot.", as in the case of the actual cartidge design of the .22PPC, 6mmPPC, or the new crop of short and super short magnums, I could have bought it! As to why spacing off the shoulder instead of the belt, as with the case of the new beltless mags is prefered, that is another can of worms!
anodes.

 

[jamullins]

in the case of the .222 it is due to the length of the case neck, it can seat a longer bullet withouit sacrificing case capacity than the .223. Most references to inherent accuracy come from a comparisson between bullets of a given erqa in regaurds to velocity. the .220 Swift is inherently more accurqate due to its high velocity producing a flatter trajectory and lower recoil impulse than the .25-06 of the same era. Nowadays we have the 7mm ultra, thew 30-378, and so on that are noted for their inherent accuracy. again it comes from the velocity flattened trajectory and lower recoil impilde than other noticably more powerful long ranre rifles. Here is an era specific equivalant, in it's day the .243 was noted as being inherently more accurqate than the .308 Winchester.
As for actual inherent accuracy as opposed to comparative, some rounds exhibit a tendancy towards better accuracy due specific conditions. the 6.5x55 mauser round fired an unusually long and heavy bullet of 160 gr in its original military loading. Given its velocity and the ballistic coefficient of the bullet it made for a highly accurate rifle in the right hands. the .222 and the .223 are both inherently accurate due to a flat trajectory and low recoil impulse that make them easy to handle. the .50 browning is inherently accurate due to its weight and the momentum it generates. the bullet remains remarkably stable in flight over long distances. It is ikmportant to note that some cartridges are only inherently accurate when loading into the right guns, weatherby rifles were originally mabufactured with a bit of extra free bore because of high pressure levels at the breach, nowadays they are still manufactured with said freebore so the weatherby rounds tend to be more accurate in other manufacturer's rifles that posses less freebore due to tighter tolerances. The .300 whisper only exhibits it remarkable accuracy with super heavy 250 to 260 gr match bullets with a very low drag inducing shape and huge ballistic coefficient. I know i ramble, its the cafine, i hope this has helped more than it confused.

 

[Rich Z]

Maybe a definition of "accuracy" is in order.

When I speak of "accuracy" I guess I am really talking about repeatability. In other words, all other factors remaining constant, subsequent rounds fired in a gun will impact in the same identical spot for a 100 percent "accurate" round. Which rounds are most inclined to have this "repeatability"?

Yeah, this is ivory tower stuff, but it is one variable in the mix that I would like to see discussed in more detail.

Flatter trajectory may mean that impact at 100, 200 and 300 yards will not vary much, but has nothing to do with the grouping at any one of the three distanced targets.

Hope I expressed this well enough.....

 

[jamullins]

by accurracy in shooting you are talking about the ability of a weapon/cartridge combination to be made to hit a desired point of aim. So, yeah, you want to be able to set up a rifle to hit a point of impact over and over again. having a flatter trajectory just means less compensation due to less bullet rise over distance, it sort makes it easier to judge where to aim a rifle to get a bullet to impact. group size over range only opens up becuase as range increases the degree of percision as shooter can achieve is marginalized due to about a gazillion factors.

 

[anodes]

RichZ, I get you and agree that bullet drop has little to do with "repeatable precision placement" when it comes to the seemimgly over used term "inherent accuracy". Bullet drop, when all factors are equal, will be a measurable and there after predictable effect based on drag and gravity alone. This can be compensated for and reduced to a practical zero variable in some few ways; first, a laser range finder and ballistics chart for your given load. Second, shooting a known distance coarse and using the same ballistics chart. Other factors to be compensated for in reducing the variable of drop would be: wind (leading or following), temperature, pressure, humidity, bullet wieght and ballistic coeffientcy of the projectile. All of these factors regard to drag and can be measured and there by have their effects on bullet drop be compensated for and reduced to, as I said, a "practical zero".

Therefore, we can eliminate bullet drop from the equation that we are trying to "inherent accuracy". Wind as a crossing effect is more responsible for a left/right stringing and we could reduce this variable by measuring a vertical group size with regard to "inherent accuracy".

We can also eliminate terminal ballistics from the equation. The expansion rate, wound channel and bullet path are irrelevent. Repeatable shot placement is all that matters and after the proj. peirces the paper/skin, terminal ballistics begin.

We are left with internal ballistics and external ballistics.

External ballistics are effected mostly by the two aforementioned factors: drag and gravity. The true relationship of these factors was eventually determined by the inventor of the ballistic pendulum, Benjiman Robbins. Sort of a crude chronograph, with it he was able to find the remaining energy of a projectile after a known distance and knowing the wieght of the proj. determine the velocity at impact. The ratio is a whopping 85:1! That is air drag has 85X the effect on a proj. than gravity. And ever since, ballisticians have been trying to decipher the most perfect and truest effects of drag on trajectories. These effects are stated in part above: temperature, pressure (altitude), humidity, distance to target and leading or following wind.

NONE OF WHICH I feel relate to the basic design of a cartridge or it's "Inherent Accuracy"!

Except for two factors... Sectional density and ballistic coefficient. A small mass with large cross section (pingpong ball) will be more effected by drag than a similar shape of higher density; a lead pingpong ball will fly further and a hollow, plastic one. Simply put, the ballistic coeficient (C= w / (i x d<2>)) is the wieght/("form factor"x diameter <sq>). All this means is finding out "how much" drag effects and certain bullet shape. i.e.- "long and pointy" IS better! The basic cartridge design that can accomidate bullets of prefered S.D. and B.C. are MORE INHERENTLY ACCURATE.

That leaves internal ballistics!

The firing pin ignites the primer causing an explosion that, in turn, ignites the powder developing an expansion of burning gasses. These gasses develop more preasure which increases the burn rate of the powder until the gas pressure overcomes the friction of the crimp that is holding the bullet. Yeah... yeah... WE KNOW!!! The rest of it; the bullet passes the "leade" and engages the rifleing, pressure is still building, the bullet begins rotating and accellerating and pressure is still building until, at some point, the pressure begins to decrease due to the expanding volume of the bore behind the bullet. This continues until the bullet leaves the muzzle. However, this pressure wave is still there and can effect the bullets flight path even after it leaves the muzzle (that's why my M1A flash hiders are taper reamed to M21, MTU specs... but that would be external ballistics ).

Discounting rifle to rifle variations in the cut of the bore and lands and crown of the muzzle, which in thier way DO effect accuracy, but NOT the "inherent accuracy" of any cartidge design, we are left with the ignition, detonation and subsequent build up of pressure of our powder as it relates to case shape (internal and external), primer consistancy and flash hole size and uniformity. Primer consistancy is NOT case design and can be dropped from the equation as a variable. Yes, it will effect your accuracy, but should NOT be considered as a variable w/regard to "inherently accurate cartridges" because you can use the same primers in any two cases and have only the variables of flash hole shape and size and case shape and size left as unique.

So there it is! Case shape and size and flash hole shape and size as the remaining design factors that contribute to any ONE cartridge being MORE accurate than any OTHER. As I said above:

Now if they had gone on about "a shorter powder column gives a more consistance burn pressure from shot to shot.", as in the case of the actual cartidge design of the .22PPC, 6mmPPC, or the new crop of short and super short magnums, I could have bought it!

And for me, that's about all there is to "inherently accurate cartridges"...
anodes.

btw, Rich, I put a recliner in my Ivory Tower...

 

[Rich Z]

I guess what brought this to mind was when I was at a gun shop recently, they had a couple of boxes of 223 WSSM (I think that is it) so I took a peek at the rounds. Now I have heard people say that the 22-250 is a "inherently accurate" cartridge, and I am curious if the new short magnums coming into vogue will be "inherently accurate" cartridges based on the shorter wider cases they have.

At one time I was looking at getting a 25-06 rifle, but I took a look at the ballistics tables, and a 100 grain bullet fired from a 25-06 is very similar to a .243 with the same weight bullet. So I started asking around, and many people said the .243 was "inherently" more accurate than the 25-06.

Now there are a lot of issues here. A 100 grain bullet in a .243 will be narrower, which means it will be longer than a 25 caliber bullet of the same weight. But there will be a limit to where a bullet is TOO long and will not stabilize properly without a faster twist rate in the barrel.

So maybe the issue is a particular bullet style, shape, and weight/density, being propelled at a particular velocity down a barrel with a specific twist rate. And I agree, that yes all these factors are important (and we can go in to great detail about resonating frequencies of a barrel as well), but I want to start at ground zero. Is there a particular design of a cartridge that tends to be more accurate than others? Are shorter squattier cartridges more accurate than long narrow ones?

A couple of years ago I decided to experiment a bit. I was using one of my Colt Pythons, and made up test loads in .357 mag using samples of every type of powder I had laying around here. I made up a box and varied the loads by 3 tenths of a grain staying in the middle of the recommended loadings.

I then went out to my range and used a separate target for each 5 round group. I discovered that, with everything else being equal (as much as can be), the powder charge weighting didn't have all that much effect on the groupings I was getting. However the TYPE of powder made tremendous changes in group impact centers! Dramatically so. We're talking about one group being at 2 o'clock, whereas others being at 7 o'clock. So easily it was apparent that the type of powder used could make as much difference in adjusting bullet placement as adjusting the sights.

So I imagine rifle cartridges are likely going to be the same way, but haven't played with that yet.

When you think about it, trying every combination possible in your gun to try to figure out the *BEST* most accurate load would probably leave you a worn out barrel before you tried them all. Oops! How did this message get into reloading?

 

[jamullins]

i think the only thing inherent about firearms accuracy is all the b.s. guys like us manage to come up with in order to explain how it works to each other when we are the ones who have already tqaken the time to figure out how to acheive accuracy!

 

[Rich Z]

I understand. What I am trying to do is to take some of the variables (if possible) and make them into constants. Trying to remove some of the voodoo in all this. Still, I suspect that even using all the right components will still make a wrong combination more times than I would like.

 

[anodes]

I'm almost ready to say, "The Hell with it!", and drop down to 3 cartridges; the .22LR, .308 Win and the 375 Wea! That should about do it! <more on that later! > But instead of owning less, the manufacturers want us to own MORE! Thus the constant development of new and "better" carts and rifles to shoot them in! All hype? I think not, dispite or perhaps because of, how much I wanted that cute lil' Rem M7 in .300RUSM! That looked like one sweet combo! Dispite my own cynicism, if the .300H&H or the .45-70Gov were all that they could be, there would have been no successful development and subsequent acceptance of the .22 or 6mm PPC. Each accepted by the benchrest guys as worthy improvments to established cartridges in equivelent caliber. It is reasonable to admit that there IS room for improvment with our shooting hardware and philosophies. And shorter, fatter carts seem to be the current trend...
anodes.

 

[jamullins]

i feel a good definition for inherent accuracy would be a cartridges ability to be successfully made to produce consistant and precise shots from a suitable firearm when employed by a shooter using proper and safe firing technique.

as for inherently accurate cartridges of my own belief. I think the .308 winchester is one of the finest. I feel that accurracy is best acheived through moderation of power and velocity. loading strictly for one or the other i feel takes away from the overall effectiveness of the cartridge. to me a .308 is one of the best combinations of power and velocity in a single cartridge when done with the attitude of moderation. after all all the bells and whistles in the world are just so much junk if the man doing the shooting hasn't even learned basic firing technique with enough proficiency to realize where the edge technology can provide would be beneficial or just lessen his margin of error by a small degree. damn, did i say all that,did it make sense!

 

[anodes]

lol, Yes you did and yes it did!

However, by your definition an "inherently inaccurate" cartridge would be a heavy kicker like the 458WinMag in the hands of an inexpierianced shooter suceptable to flinching. Turn that rifle/cart around to the hands of an expierianced shooter and it becomes "inherently accurate" (if shot well). And that's where we differ. When I was working for a company that manufactured ceramic ballistic armor, our test "rifles" were blanks >3" in dia, clamped into a vice bolted to a heavy table in an under ground range, w/a laser shot down the bore for alingment. This is a scenario that I was envisioning to use to determine a specific cartidge designs "inherent accuracy". One that eliminates all factors and variables such as shooter error and so on. One that only quantifies internal and external ballistics of any specific cartridge w/a minimum of contributing hooey! Btw, the test criteria for "the product" was <3/4" depression into modeling clay under the vest, after fireing a .30-06 AP from a distance of ~30M. Anyway, we had blanks of many calibers and chambers for use in such testing. Would be the ideal setup if @ longer range. I can't tell you how long I've wanted a 200yrd underground range!

I will agree w/you that the .308Win is a GREAT cartridge that would make it into my "Top 3 of all time" list. I also agree that there are times, many times, that you should and must include shooter ability in rateing any cartridge, depending on the criteria.
anodes.

 

[Bolo]

OK! - Gonna me break out my reloading manual

It's the "Ballistic Coefficent" that keeps the bullet spinning true for _long_ ranges = Long heavy boattailed spritzer bullets.

According to the published BC's in my old Sierra Manual, the top 3 calibers (in descending order) are the 7mm, the 30cal. (7.62) and the 6.5mm.
After these 3 comes diameters like 6mm and .22 cal., all accurate in the right loadings in the right rifle with a good rifleman. :dunce:

Best way to tell is to stop analizing and start utilizing
Compare targets, not statistics...:dgrin:

 

[jamullins]

a thought........

the army trains thousands of first time shooters annually, many of whom learn to fire the M16 with impressive results for someone with no other training or experience with firearms. there are a number of these new shooters who will go on to the army marksmanship unit to be trained as a sniper as well after they have been identified in a given unit as the 'guy' deemed to be worthy of said training. some of these new shooters will also do well with the M24 while others will not and flunk out.

so while the .223 is inherently accurate because inexperienced shooters can easily learn to become quite proficient with it quickly is the .308 void of the same inherent accuracy becuase not all of these new shooters could learn to become as proficient with it as well? believe me i do understand the arguement of what constitutes inherent accuraccy, and i sympethise with the rest of you over how to clearly define what inherent accuracy is and which cartridges possess inherent accuracy.

 

[eli95]

Results of 30+ years reloading

1. Any cal can to be made to shoot accuratley!

2. Off the shelf accurate guns are those that match twist rate to bullet weight the best. (stability of bullet in flight)

On the 308, I agree that it is good, but drive the velocity up and bullet weight down with a slow twist barrel and see what happens.

Try a 45-70 of new manufacture and try to get good results with cast bullets and velocity over 1400fps.

All these things have to come together or the results will be inaccurate shots.

I have found that my 1885 Browning doesn't like velocitys over 2000fps with jacketed bullets,(besides the shooter gets flinchy after two shots), and 1600 with cast bullets.

Terry

 

[Tim Madsen]

Inherently accurate= a term someone made up to make it sound like they know what their talking about.

 

[anodes]

TM, Welcome! And a Happy New Year to you and yours! Ditto on that! `Ol Craig Boddington just can't seem to stop himself, in the latest G&A (02/04) he states, "...the Hornet (.22 Hornet) is not an "inherently accurate" cartridge to begin with...". And, "Today's .22 centerfires are faster and more "inherently accurate" than the Hornet." But doesn't explain his criteria of WHAT makes it more "inherently accurate" or why. He does state that it is, "...partly because little research and development has gone into Hornet loads in the last 50 yrs.". But hypocritically undermines his own judgement of the "inherent accuracy" or LACK of it re: the Hornet by implying that the accuracy is not in the design of the cartridge but in the LOADs used! That doesn't seem to stop him from coming up w/2 pages of "a load" himself regarding the "inherent accuracy" of the Hornet!
anodes.

 

[Guest]

since nobody can consistently deliver

hits on 1 moa targets, under field conditions, anyway, all this sub 1/4 MOA talk is just meaningless bs.

 

[Rich Z]

Well, I agree, but all things being equal, I would rather be using a gun/ammo combo that could deliver such consistent accuracy if the shooter is able. If I miss, I want to be able to blame myself, and not the gun. Sometimes just the confidence knowing the gun is up to the task can influence the WAY you shoot.

 

[Guest]

agreed, but I'll take high retention of velocity, with its reduced drop and drift, over somewhat tighter groups, any day. A 2" group at 400 yds, 4" off of the 2" target, is not nearly as good as a 4" group, centered on that 2" target. The latter, you hit almost 50% of the time. The former, you miss every time.