25 March 2011, 04:14
WarriorThe Holy Grail of Accuracy
What is acceptable accuracy?
Introduction:
We often read or hear people saying that a particular cartridge is very accurate, because they have had only good results from it. Can we blame people for saying that? Generally most 222 Remingtons are very accurate and many competitions are testimony to that. We all know how well the 6 mm PPC is doing in competitions - with its short stubby case. Why is the 308 Win, with its shorter case, today preferred over the 30-06 Spr for Palma competition shooting? It shoots the same bullet, only the case differs. When the first 7 places are taken by the 6.5-284 Norma in a recent shooting competition, do we then attribute this accomplishment due to the cartridge design? The 284 Win never developed a following and is near extinction now, but it seems to have a new lease on life through the necked down version of 6.5-284 Norma. The quest to understand and explain, makes ballistics an interesting subject and as it evolves over time we sometimes need to re-explain ourselves.
Does accuracy primarily come down to case design - having a short powder column? Apparently it burns better, but combustion still takes place well into the barrel. Winchester has just started a short and fat case revolution in most of the calibers with their WSM. Sako goes the other way - they have just released a 9,3 x 66 mm! In the big bore arena, the case of the 458 Lott was extended by 4.8 mm, and the 458 Express was born. It is quite the opposite of a short stubby case ... and it shoots clover leave groups! The purpose of my article is then to explore whether the term "inherently accurate cartridge" is misleading or not, and what role precision loading of ammo and the rifle play in the accuracy equation?
Somchem's View:
Johan Loubser, former ballistic expert of Somchem, wrote that:
• Accuracy is totally independent regarding geometry of calibre
• There is no magic in case design to enhance barrel behaviour
• Cases cannot be described per se as accurate or inaccurate
• Case fit to chamber is critical for alignment/concentricity to the bore
• Propellants cannot be described as more or less accurate
• Primers cannot be described as accurate or inaccurate
• Projectiles can be described as marginally more or less accurate
• The barrel must have stable harmonics
• The shooter is the weakest link by far in the accuracy chain
Required Accuracy:
Generally 1 MOA is good enough for hunting purposes and .5 MOA is considered sterling performance, but is this good enough for 1,000 yards shooting competitions? Never in your life, as many other factors creep into the equation when we check our groups beyond 100 m. I load very carefully for all my rifles and try to obtain the most accurate load possible. With my 7 x 57 mm, I get 10 mm groupings at 100 yards, which I think is fairly good for a Mauser K98 action. With my 300 H&H, with its much longer case, I get 5 mm one ragged holes. This is contrary to the short case theory, not to mention the substantial recoil differential. My 9,3 x 62 mm yields 9 mm groupings. My son's 375 H&H also gives regular 12 mm groupings, despite higher recoil than the aforementioned. All these rifles have been built on Mauser K98 actions and they fit their purpose very well as hunting weapons. This leads me to the question, whether or not, the WSM that is supposedly inherently more accurate, will make a practical difference for me in the hunting field.
Benchrest Shooting, is a sport for those that are obsessed with perfection and it demands the utmost from it's shooters and their equipment. A Benchrest rifle and load is at the cutting edge of technology. Here we talk about extreme accuracy at 900m (1,000 yards). The following are the current world records from the International Benchrest Shooting Association. The size of the group is measured by the outside diameter minus the diameter of the bullet (as measured in thousandths of an inch) to determine the actual group size. Groups are quite a bit better than ¼ MOA at 100 yards!
Rifle Category -------------- 100 Yds --- 200 Yds --- 300 Yds --- 1,000 Yds
Sporter Rifle --------------- 0.066" ---- 0.140" ---- 0.329" ---- n.a.
Light Rifle - 10.5 Lb limit - 0.059" ---- 0.134" ---- 0.240" ---- 1.996"
Heavy Rifle 13.5 Lb limit --- 0.052" ---- 0.109" ---- 0.259" ---- 3.472"
The .222 Rem will shoot with the PPC’s at 100 yds, but are too wind sensitive to compete at 200 yds. Almost all, current 100, 200 and 300-yard records are held by the 6 mm PPC. The 70-grain bullets of the 6 mm PPC in turn, lacks high enough BC’s to be competitive at a 1,000 yards. The 6-284, with a fast twist of 1in 9”, which is capable of stabilising 107-gr VLD bullets, do have a better chance to compete at such a long range. However, it is being overshadowed by the 6.5-284 Norma, as 6.5 mm bullets ranging from 139 grain to 142 grain, have some of the highest BC’s to be had. Even so, factor in that the 6.5 mm Berger 140-gr VLD bullet (BC = .622), that starts out at 2,950 fps drifts 62 inches at 1,000 yards in a 10 mpu in crosswind, and you will understand why this game is the ultimate challenge of marksmanship. The bullet drifts 6.2 inches for every 1-mpu wind, and we know that wind never blows consistently. The wind is the toughest nut to crack, not bullet drop! That is why the PPC's are not doing so well in the Annual Varmint Hunter Jamboree Shootout, against other 6 mm cartridges that shoots heavier bullets with higher BC’s, as there are no wind flags to guide the hunter in the field, no meter to measure the wind and no calculator to calculate how many clicks to move the dial of the scope - huh! So, practical accuracy is not the same as on the bench - it is horses for courses!
Just for the fun of it, I am going to define accuracy. Accuracy is how far the hit was from where it was intended. In other words, how far did I miss the bull? Precision refers to the dispersion of the hits - i.e. the extreme spread. In other words, how close is the grouping of the shots. Once I have an acceptable group, I can adjust my sights and bring the shots to the bull. So, from now on I will be talking about precision and not accuracy, as the subject is about how scatter shooting can be attributed to a specific cartridge. Thus, I will be referring to precision loading, precision shooting and precision made rifles. If we want absolute precision, we need to optimise all the variables that can play a role and I propose to group them under 10 headings and discuss them individually. Variations in factory made rifles are vast, whereas in benchrest rifles, at least, we know extra care has been taken to produce precision instruments.
1. The Case
In the extreme accuracy sport of benchrest shooting, where all compete with precision ammo and custom build rifles, the main difference seems to be case capacity and the resultant recoil it produces. No cartridge using a magnum case, a standard capacity case (.30-06 size), or even a normal short action case (.308 size) can compete with those that employ smaller cases, of which the 6 mm PPC is the best example. Small bore calibers, by their very nature, are best suited to small cases, and with their lower recoil it is a pleasure to shoot them. I do not believe there is any magic in case length or shoulder angle that confers a special level of precision on any cartridge design. The .222 Rem and the .223 Rem fared extremely well in competitions, but they do not have short stubby cases - all we can say, is that their powder capacity is relatively small. In the same vain, the popular 308 Win has a smaller powder capacity than the 30-06 Spr and many competitions showed in fact, that .308's win over the 30-06’s.
Case selection and preparation though, is very important. Competition shooters turn case necks and use once fired cases to get even pressure around the bullet and to get perfect line-up between chamber and bore. ‘Flashole uniforming’ is done to get the same flame release into the case. Not all cases are created equal even though they come from the same manufacturer - they differ in weight and volume. Cases that do not weigh the same get rejected, as their powder capacities will differ. Differing case capacities will yield different pressures and hence yield different velocities that will increase the group size on the target. Custom made benchrest rifles usually require that case necks be turned to precisely match tight chamber dimensions, unlike when reloading for hunting rifles with chambers of standard dimension.
The new wave of Winchester to design short stubby cases, has the inherent weakness that longer and heavier bullets, will rob powder capacity. For this reason the 300 WSM must shoot 180 gr bullets rather than 200 and 220 grainers. For competition shooting this may be fine, but for hunting I much rather prefer my 300 H&H that is capable of accepting the longer bullets. A 300 Weatherby Magnum, with its very long case, also holds a world record in benchrest shooting, despite its heavy recoil.
2. The Bullet
Competition shooters weigh their bullets to eliminate weight variances. Weight variances are quite common in hunting bullets and thus they will print differently on the target, especially at longer range. Concentricity of the bullet is very important so as to minimise the yawing of the bullet. The bullet must spin around its centre of axis for best stability. Furthermore, the competition bullet is matched with the barrel's twist rate, again to eliminate an over spin, which comes into play the moment there is a slight imperfection in bullet design. Competition bullets normally go through multiple sizing dies to ensure close tolerances.
Sleek bullets with high BC's are preferable to counter wind sensitivity, especially at longer ranges. Long bullets, such as the 6.5 mm, generally have higher BC's than most other calibers, but overly long bullets rob the powder capacity, which in turn necessitates a velocity sacrifice, which again is not ideal for long range competition shooting. So, there is always a trade-off in real life situations. Boat Tail bullets with hollow points, seem to have conquered the market for match bullets.
Soft bullets, that cause more fouling, like pure copper bullets, are not ideal because ultimately it affects precision shooting adversely. For this very reason, Barnes have just brought out their Triple Shock bullet, with 'relief bands' around the shank of the bullet, to make space for the surface flow of the copper and they found that the sustained accuracy was better than the Barnes-X bullet. Jensen's bullets are unique in that they are made from a copper-nickel alloy, rather than pure copper, which means they yield less fouling. Oversized or undersized bullets can also affect precision, but this is not really a problem with Match bullets that are meticulously made - generally to groove diameter, which is slightly bigger than bore diameter.
3. The Loading Process
This requires precision and consistency in the powder charge to yield velocities with a minimum variation within 5 to 10 fps. Variations in velocity of 50 fps and more, is not conducive for precision shooting. Typically a case fill of at least 90% is needed to ensure that the powder column is stable in the burning process. The burning rate of the powder selected, must be in harmony with the size of the case to get a complete powder burn within acceptable pressure levels. It is known amongst reloaders that when one switch from one powder to another, that pressures are likely to change, the point of impact will change and even the group size in some cases. The main point is that the measured velocity must be as close as possible to obtain close groupings.
Bullets must be seated perpendicular. Bullets that are slightly tilted in the case, i.e. poorly seated, will engage in the rifling of the barrel with an angle which does not make for a stable bullet as it leaves the muzzle, as it will no longer gyrate around its original centre of axis. Competition shooters use expensive high precision seating dies, unlike hunters. Utilisation of precision made custom dies, is an attempt to get the bullet to enter the barrel perfectly concentric. Furthermore, competition shooters play around with seating depths to fine-tune their groupings. Generally bullets are seated to a 'near touch' to the rifling, to ensure straight line engaging.
Overly long bullets, that are seated too deep into the case, is not known for yielding high precision. This could be due to an uneven release due to more powder at the bottom of the bullet's base or skewed shock waves bouncing of the case's shoulder onto the bullet in that millisecond. The ideal seems to bring the pressure to bear on a flat surface, where the base of the bullet lies flat at the rear end of the case's neck. I cannot proof this, but perhaps we should look at the bullets that are being used in those calibers that win competitions more often - for example the 70-gr bullet in 6 mm PPC, 140-gr in 6.5 x 55 mm and 165-gr in 308 Win. To illustrate I have picked Sierra’s Hollow Point Boat Tail bullets:
--------------------------- 6 mm PPC ---- 6.5x 55 mm --- 308 Win
--------------------------- 70 gr HPBT -- 140 gr HPBT -- 165 gr HPBT
Cartridge Overall Length -- 52.71 mm ---- 80.01 mm ----- 71.12 mm
Case Length --------------- 38.23 mm ---- 54.99 mm ----- 51.16 mm
Difference ---------------- 14.48 mm ---- 25.02 mm ----- 19.96 mm
Bullet Length ------------- 21.08 mm ---- 33.53 mm ----- 29.72 mm
Seating Depth ------------- 6.60 mm ----- 8.51 mm ----- 9.76 mm
Length of Case Neck ------- 7.65 mm ----- 7.82 mm ----- 7.72 mm
All three cartridges seem to fit the theory pretty well, but the 6 mm PPC is certainly the best placed, followed by the 6.5 x 55 mm, and then in third place the 308 Win. Going to the 30-06 Spr, the long 190 gr Sierra match bullet, seats 13.18 mm deep whilst the neck length is 9.79 mm - the worst of the bunch. The 6 mm PPC holds more records than any other cartridge. Ideal bullet fit, low muzzle blast and low recoil all help. Still a mystery ... ?
Then there is still the debate as to why the 308 Win shoots better groups on average than the 30-06 Spr? Bart Bobbit did an article on this and can be seen at
www.snipercountry.com/c-s-3.htm. He sites the example when the 30-06 Spr was still allowed in Palma competitions, when the 308 Win out performed it consistently. He further states ... "Most top highpower shooters feel the main reason the .308 is much more accurate than the .30-06 is its short, fatter case promotes more uniform and gentle push on the bullet due to a higher loading density (less air space) and a more easily uniform ignitable powder charge." My comment would be:
a) Bullet fit would not really be an issue when a 165-gr bullet in a 308 Win is compared with a 180-gr bullet in a 30-06 Spr as seating is about the same, so the push on the bullet should be equally even. Bullets ranging from 165 grains to 200 grains were used in the 30-06 Spr.
b) The propellant is not the same - the 308 Win needs a faster burning powder than the 30-06. In the South African context we would load with S335 and S365 respectively. Somchem argues that this would not make a difference except if nominal charges were to be used. However, if loading densities differ, the comparison leaves room for another variable that can play havoc. Differing 'case fill' ratios between a fast and slow burning propellant may play a roll. If less air space becomes a critical factor, then a 100% case fill should be opted for and not 90% plus.
c) Sure a fast burning powder would burn quicker in a short case like the 308 Win, but the burning question is whether it will yield better groups. Somchem argues, that there is no magic in case design to effect or enhance barrel behaviour. The bullet must enter the barrel perfectly, go through at least 24 inches of barrel with pressure behind it, and exit the muzzle perfectly to have a stable flight.
d) A twist rate of 1 in 12" (308) is more ideal than the 1 in 10" (30-06) for a 165-gr bullet. The 1 in 10 " twist of the 30-06 Spr was designed to stabilise 220-gr bullets and provides an over spin for lighter bullets. The 1 in 12" twist on the other hand is absolutely ideal for a 165-gr .308" bullet. So, the only way to settle the score, is to have the same twist rate for both cartridges and the same 165-gr bullet should be used. An over spin may induce or exacerbate bullet wobble (yaw) - a yaw of as little as a degree or two, can have a substantial influence. I assume throats were equally precise, and the same barrel type, same quality, and same length and rigidity on average, otherwise we open another can of worms. I believe this is an aspect that is overlooked or underrated by many people.
e) The recoil of the 308 Win is generally lower than the 30-06 Spr with its greater powder capacity.
f) Lastly, the shooters were different, i.e. marksmanship.
4. The Throat
This brings me to throat variations in different calibers. We know that the 308 win has a shorter throat than most European calibers (e.g. 7 x 57 mm and 7 x 64 mm). Typically shorter throats go together with tighter chambers and benchrest shooters prefer this high precision. A longer throat will reduce pressure for military and hunting cartridges, but that is not the main objective for precision shooting in controlled environments. When the line-up of the bullet in the chamber is perfect with the bore, the extra jump in the longer throat does not seem to affect accuracy adversely. However, if it is not the case, then the extra distance between the bullet and the rifling, can only make the situation worse.
Truvelo advised me that they optimised their 308 Win Target rifle for the 155-gr Palma bullet. Firstly, they cut the leade shorter, so that the bullet has to jump less than 1 mm and both throat and barrel dimensions are tighter than for their hunting version. Interestingly enough, they also changed the twist rate to be slightly slower at 1 turn in 12.5 inches, as 155-gr competition bullets are shorter than 165 grainers. Even changing the twist rate by a mere half an inch was considered necessary. As I believe that the twist rate factor is a significant one, I fully support their decision. The best testimony that it works fine, is the fact that a South African won a first place recently in a British Palma match with one of Truvelo’s target rifles. 30-06 Spr competition die-hards, better start looking at twist rates. The potential for overspin is even greater with ‘light for calibre’ 110-gr .308 bullets and when combined with a low BC, it becomes a non-starter.
5. The Barrel
The heart of the rifle is the barrel. None of the factories makes a barrel capable of winning benchrest matches - at least, none has in the last twenty years or so, but most Remington, Winchester and Sako factory barrels will shoot sub-half MOA groups. Suffice it to say, that only a barrel from one of the makers of high quality benchrest barrels is up to the task of precise long-range shooting, shot after shot. The barrel is probably the most critical component, when it comes to long-range precision shooting. A good benchrest rifle will have a precision custom made barrel.
The twist rate should be optimised for ‘bullet length’ in a specific calibre and it should be uniform throughout. Precision standards for deviation of bore and groove dimensions are of vital importance for precision shooting. Hand lapping of the barrel is done to ensure a smooth surface to minimise fouling. Match barrels get graded according to precision standards. It should be finished off with a perfectly cut crown. Some crowns taper in at 11 degrees and others are perfectly square. The barrel should be stable or consistent in its oscillations and for this reason, all match barrels are stressed relieved.
Longer barrels for competition shooting generally ensure lower pressure at the muzzle, with a concomitant lower muzzle blast, to minimise the shock wave of the gas on the bullet parting with the barrel. Since longer barrels sag more, they are made thicker to stiffen them up again, as rigidity is important for continued precision shooting. Long-range competition shooters seldom use barrels shorter than 26 inches - typically they vary from 27 inches for a .308 Win to 30 inches for a 300 Win Mag. Barrel length is an important consideration when one is looking for top velocities, especially when burning the slow powders. Top velocities, means less bullet drop and less wind drift for them, but there comes a point of diminishing returns, where additional barrel length, will not yield more velocity.
We also know that no two barrels are alike and that makes it difficult to say one cartridge is more accurate than another. My contention is that the quality and the precision of the barrel, plays a far bigger role than powder column variations, in terms of case design. Furthermore, the powder is not fully burnt in the case in any event - it goes well into the barrel before that is achieved. It does yield slightly higher velocities though, for the same amount of powder, but we cannot say it enhances precision shooting. Factories will serve us better if they fit precision made barrels to our hunting rifles as opposed to changing the design of the case.
Daniel Lilja is a barrel maker from Plains, Montana. Lilja worked as an industrial engineer for the John Deere Company in Iowa before he started in the barrel making business in 1985. He is a benchrest shooter and past director and president of the National Benchrest Shooters Association. His barrels have won every major benchrest tournament across the USA. Hunters, varmint shooters, the US Armed Forces and every major bullet manufacturing company have bought his barrels for their well-known accuracy. Lilja considers a constant rate of rifling twist throughout the bore extremely important to accuracy. Also, a difference in groove depth as slight as two- ten thousands of an inch can cause bullet imbalance. "The geometry of the rifling has to be true all the way down the bore," Lilja said. The standard Lilja barrel has six lands and six grooves. The lands cover 25 percent of the bore circumference, but 'land size' is a trade-off. Narrow lands distort the bullet less as it passes, but also burn away faster from powder gases. Wide lands on the other hand, increase pressure because of the added resistance on the bullet. Lilja also makes some three and four groove barrels and their wider lands resist erosion and heat better than narrower lands. Hand lapping is also considered by Lilja, as most important for precision shooting. Finally, Lilja checks with a bore scope for blemishes and on a Shefield air gauge for variations in diameter, before the barrel is passed.
6. The Trigger
Regarding triggers on hunting rifles, Winchester is ahead of Ruger, and Remington in turn is ahead of Winchester. Ruger’s standard trigger is not even adjustable. Custom triggers are far superior and more expensive than standard factory triggers. Jewell makes replacement triggers for Remington and Winchester, but putting one on a factory rifle is normally too pricey. Savage, introduced their latest trigger called 'Accutrigger' in January 2003 and so leapfrogged all factory-made triggers. They say that it ... "is much smoother, crisper, broke cleaner and demonstrated less creep than any other factory-built trigger tested".
A custom trigger belongs on a more expensive custom rifle, where extreme accuracy is the objective or where price is not the main consideration. Custom triggers can be set as low as 2 oz, which is of course way too sensitive for hunting purposes. Adjustable triggers on hunting rifles generally cannot be set lower than 1.5 pounds. Military Mausers, with a 5.5-lb trigger pull, is definitely not conducive to precision shooting.
7. The Action
A short cased cartridge, do have the benefit of a shorter and more rigid action, which should in theory improve precision. A stiffer action is less of a factor with the smallish cartridges, that have a low back thrust onto the bolt, such as the 223 Rem and 6 mm PPC as opposed to more powerful cartridges. In addition, the 6 mm PPC is primarily built for a competition shooting in sturdy benchrest rifles with heavy actions in any event. So, it is more of a factor in lightweight and longer actions, which is typically fitted to hunting rifles.
The military K98 action was primarily designed as a military action and not for competition shooting. Its bolt and action will flex, and the thumbcut that weakens the receiver, is not helping either. Clearly, it is not ideal for competition shooting, but I achieve very acceptable precision for hunting purposes with them. Both Remington and Winchester actions are stiffer in comparison, and many of their rifles shoot worse than my custom built Mausers. I guess, because the line-up between chamber and bore is pretty good in my rifles, concentricity plays a bigger role than action flexing due to the back thrust when a shot is fired.
A ‘benchrest action’ is much stronger and rigid and therefore provides a more stable launching platform, which makes a difference on the longer shots. So the type of action can play a role. Just to illustrate the low back thrust of the 6 mm PPC, relative to some other cartridges used for competition shooting:
------------- Max Inside --- (A)-------------- (B) -------- Ave. Operating (A x B)
Cartridge --- Case Dia. ---- Area ------- Chamber Pressure --- Thrust in pounds
6 mm PPC ----- .378" ---- .112 sq. in. -- 45,500 psi --------- 5,096 ( 70 gr @ 3,000 fps with S335)
308 Win ------ .400" ---- .126 sq. in. -- 59,500 psi --------- 7,497 (165 gr @ 2,700 fps with S335)
300 Win Mag -- .445" ---- .156 sq. in. -- 58,411 psi --------- 9,112 (180 gr @ 2,960 fps with S365)
The strength of modern steels, its dimensions as well as its ability to flex are the factors that determine how the back thrust is handled. To make a quality action, custom gun makers go beyond what factories offer the hunter:-
• Receivers are precision machined from pre heat-treated steel with carbide tooling.
• Only the very best steels are being used.
• No forgings or investment castings are being used such as for hunting rifles.
• Highest quality components, regardless of cost, are being sourced.
• Use of precision chamber reamers for the highest degree of precision.
• The bolt is absolute true, concentric and tight fitting and lapped for a perfect fit.
• Enhanced recoil lugs are used to add rigidity, which prevents action flexing.
Quite a few high precision custom actions are available for competition shooting such as Stolle, HS Precision, Viper, Hall, Borden, Barnard, RPA, and Nesika. Nesika Bay Precision, makers of world-renown competition bolt actions and rifles, claim that their manufacturing techniques are equalled by nobody ... "No one else matches our precision, our tolerances, our quality, or our customer service." Benchrest rifles employ very stiff, single-shot actions that are much stronger than hunting bolt actions as weight and portability is not such a problem.
8. The Assembly of the Rifle
A good benchrest rifle will have everything square and true, a bedded action, a precision custom trigger, with a precision custom made barrel. The chamber of a barrel must be cut correctly and share the same centre with the bore - this is vital. This sounds so easy, but this precision seldom happens in factory assembled rifles as cost is mostly a criteria. Again, it is probably more true to talk about a precision rifle, than an inherently precision cartridge.
The action must be correctly bedded to the stock to provide stability. Various bedding systems are in use to provide additional stiffness, such as aluminium blocks and pillars. A fiberglass stock is mostly used, as it is not affected by weather, temperature, or humidity changes. Unlike a wood stock, it stays consistent in all weather conditions. Most competition shooters regard McMillan’s fiberglass stock as the strongest and most rigid.
‘Balance and fit’ is important as rifles are custom built for individuals. A 6 foot 6 inches man clearly needs a longer rifle in terms of length of pull than a man that is only 5 foot 6 inches tall. Thus, to balance the rifle with the longer stock, a longer barrel is needed.
Extreme precision demands extreme measures. Aids such as steady and adjustable benchrests, with a leather cushion, wind measuring instruments, altitude and temperature meters, are used to place the bullet where intended at long range. Some use computers with ballistic programs as well to re-compute the bullets flight under actual shooting conditions. A good quality scope is need that gives a clear and bright picture at 1,000 yards, because if you can't see it, you can't hit it. These long range scopes cost more than most hunting rifles. Simply put, benchrest shooting as a sport requires the absolute best if you want to win matches.
9. Recoil
High recoiling rifles induce flinching on shooters that are recoil sensitive and this is not good for precision shooting. Most of us are recoil sensitive - we just have different thresholds. Generally most people shoot better with low recoiling cartridges, such as the 6 mm PPC. This is relative of course, as some shooters do shoot well with more powerful cartridges such as the 300 Win Mag. A heavier rifle absorbs recoil better and the felt recoil is less for the shooter, especially with a 13.5-lb benchrest rifle as opposed to a 7.5-lb hunting rifle - it makes a huge difference in terms of precision shooting!
10. Human Factor
After the trigger is pulled, there is a finite time before the bullet leaves the gun. During this time, the firing pin must fall, the charge must ignite, and the bullet must travel down the bore. These moments can be termed as "lock time" and "bore time". During this time, it is essential that the rifle be held steady - this is what is known as "follow through". The need for 'follow through' is more important with trigger systems that have prolonged lock times, such as the military K98 action. Remington had the shortest lock-time of production rifles, but Savage has now over taken them. However, Jewell triggers still remain in a class by itself, and it is the most preferred by competition shooters. I normally say one must see the bullet through to the target. The other aspect that is interwoven with 'follow through' is the anticipation of recoil, which results in 'pulled shots' that cause scattered shots. This is why Somchem is saying that the human factor is generally (not always), the weakest link in the chain. There is a cute saying amongst Americans that says, it is not the arrow that killed the buck, but the Indian.
Conclusion
It is clear from the above, that many different factors contribute towards both accuracy and precision.
Even if we ignore the human factor, crosswinds and having a perfect rifle made up by its various component parts, we still sit with the effect of ‘bullet imbalance’ and ‘velocity variation,’ that will cause widening groups the further we shoot; the phenomenon that a 1-inch group at a hundred yards, does not necessarily equate to a 3-inch group at 300 yards or a 10-inch group at 1,000 yards. The apparent ‘perfect’ bullet will manifest its imbalance at longer ranges. This is the reason why many competition shooters opt for handmade or custom bullets rather than factory match bullets.
Let's face it, modern hunting rifles are fairly accurate, but they are not in the same class as benchrest rifles. This is so because of hunting requirements (weight, repeat shot capability, reliability, etc.) that are different. Hunting ammunition can not be mass-produced to the same standards of custom benchrest ammunition. Since the extreme care, that competitive shooters take with their rifles and cartridges, is not normally followed by hunters, the marginal advantages, if any, conferred by special cartridge design become irrelevant. Also, the specifics of the cartridge design in itself, have little to do with real world accuracy, as outlined above. One minute of angle precision is meaningless if you need sandbags to do it – hunters need to hone their skills by shooting quick and confidently. We can then conclude, that there is probably no such thing as an inherently accurate hunting cartridge design. With good components, that are precisely loaded, we generally do improve the precision level of our hunting rifles, but when precision loaded ammunition is used in precision made rifles, the stakes improve drastically. To get ‘benchrest precision’ we have to do a lot more!
Warrior
A friend of mine and I discuss cartridges' inherent accuracy. He is of one opinion and I usually of another. It has dawned on me that when folks talk of such, there meaning for inherent accuracy may vary. What does this term mean to you? 
Please exclude any factors pertaining to accuracy that are contributed by the rifle or operator. 
Of interest I've heard the term used for the .222, .223, 22-250,6mm BR, 6mm PPC, 6.5x47 Lapua and the .308 just to mention a few. 
roger
instead of just "Transcribing" it???? 
Great responses! 
A friend of mine and I discuss cartridges' inherent accuracy. He is of one opinion and I usually of another. It has dawned on me that when folks talk of such, there meaning for inherent accuracy may vary. What does this term mean to you? 