On the .308/7.62x51mm cartridge...

[Slater]

I've heard it said on a few occasions in the recent past that the .308/7.62mm round is an "inherently accurate" round.

(1) If this is true, then why? Is it related to bullet design, weight, construction, ballistic coefficient, etc?

(2) Could the same claim be made of other cartridges in terms of "inherent accuracy"?

By "inherently accurate", I take it to mean that the bullet is somewhat forgiving of manufacturing tolerances, load variations, environmental conditions, etc. and will still deliver reasonable accuracy.

[SomeOtherGuy]

In general, short and fat cases that are filled to nearly 100% have better inherent accuracy because the powder charge has to be in the same position for each shot, due to the nearly 100% fill, and the short & fat design causes the powder to burn more fully within the case, instead of being pushed down the barrel still burning which increases variation. The .308 Win is shorter than its .30-06 predecessor and more nearly 100% full compared to later loads of its .30-06 predecessor, and when it was introduced there was an immediate improvement in long distance accuracy for skilled shooters using equivalent rifles and positions.

Today, the dominant accuracy cartridges are shorter and fatter than .308 Win. I think the "inherently accurate" designation may have been true, comparatively, back when the .308 was introduced, and simply stuck out of ignorance.

[soulezoo]

Not sure who's saying that... .308 has always been an "inherently accurate" round. More so than .30-06. What is said above about short fat cases is true, but they also tend to be shorter range paper punchers like 6mm ppc. What makes the biggest difference, effectively IMO, is bullet construction. The larger the diameter the bullet, the more the slightest difference in concentricity leads to inaccuracies. This is why .224 is more accurate on average than .338. The farther that imperfection is from the center of the bullet and the more the lead insides make up a percentage of the bullet over the jacket, the more perfect a bullet must be to be consistent. Think about a bullet spinning at 200,000 rpm with just that tad of imperfection off of the centerline and how that may affect balance and bullet flight.

Sorry, I miss read the OP... I thought he said inherently INaccaurate.
Someotherguy has a good answer.
.25-06 is thought of as an accurate round where .270 not as much. Why? Same case...

[pinzgauer]

Some of the conventional wisdom is more based on the typical rifle/pistol used than the cartridge.

270 is a hunting cartridge and never offered any match advantage over 30/06, so virtually no match rifles were made for it. Yet in the same platform (rifle) with the same parent case you will see similar accuracies as long as sweet spot bullets are used. IE: extreme BC differences avoided. 25/06, 270, 280, 30/06 all have similar accuracies with their sweet spot bullets in similar rifles.

280 was also perceived to be less accurate. But for decades was mainly sold in Remington wobbly pumps and autos. Was downloaded, not very well.

Same for the lowly 30/30... Shoot it in T/C pistols or similar it's quite accurate. I'm not even sure they chamber bolt rifle for it. Made worse by flatnose bullets. It's not an efficient cartridge by modern standards, but the big issue is the platform it's used in 99% of the time. (120 yo lever action designs)

7.62x39... bad rep on accuracy. But it's the russian platforms and loadings. One swipe of the die and it becomes 6.5 Grendel and can easily be loaded sub-moa in ARs without exotic barrels and recipes. Same general case volume, etc.

Good bullets make a big difference. Russian steel case Grendel ammo (love it) is 3 moa'ish for most. Replace the bullet with a decent one for some Mexican match loadings and folks are seeing 1.5 moa. Weigh the powder to be exactly the same and it improves more.

Same cartridge and loading, but large primer vs small can make an accuracy difference. (Big impact in Grendel, also impacts case life)

There are structural/physics differences in some cartridges which impact efficiencies and accuracy. Neck length. Shoulder angle. How the SAMMI spec was written.

7-08 had the curse relative to 308 and 243 due to sucky Remington loadings, rifles, and marketing. The silhouette and match shooters discovered it. Modern loadings are excellent, and of course the 260 is one of the hot long range cartridges.

[Averageman]

I've always found this a very interesting subject.
I don't have a lot of experience in this area, I was always pretty restricted to the ammunition Uncle Sam bought for me for the most part, so I'm anxious to see this go for 100 pages or so.

[SomeOtherGuy]

I don't have specific articles or links, but you will probably find the most accurate information on the accurate shooter and/or 6mm Benchrest sites (I think these are related), or anything written by Bryan Litz.

http://www.bergerbullets.com/bryan-litz-articles/

Runner up would be discussions on Sniper's Hide, but I don't know how that site is today; the brand changeover a few years back radically changed the basic operations of the site and I've had trouble consistently using it (i.e. being able to log in without having to figure out something new about the site's mechanics, time after time after time) ever since.

[Averageman]

The original, fairly basic and mechanical (rather than power driven, which was available.) M1 Abrams Commanders Copula had a simple but in my experience with the M2 highly accurate mount and sighting system.
I'm sure the round and weapon are fairly accurate, but that mount was golden.

[SteyrAUG]

I think it is, so long as you accept the variables such as match vs. ball and the variations in the launching system.

Hornady Match in a 700 based rifle that is properly blocked and bedded can do interesting things.

[1168]

.25-06 is thought of as an accurate round where .270 not as much. Why? Same case...

Like Pinzgauer said,
Its much about the platforms and percieved use.

Many (most?) hunting types use .270 with lightweight profile barrels and donut shaped crowns as a lower recoil alternative to .30-06 for whacking deer at 50-200 yds with said lightweight guns. I don’t think most even bother with checking zero past 100yds, except elk hunters. Available bullet selection matches these uses.

The sterotypical use for .25-06 is shooting antelope at longer ranges.

You can make similar observations about .243 vs .260. Or .223 vs 5.45. I consider 5.45 roughly equivalent to .223, but where’s the Federal Gold Medal Match 69gr equivalent loads?

[SethB]

Not sure who's saying that... .308 has always been an "inherently accurate" round. More so than .30-06. What is said above about short fat cases is true, but they also tend to be shorter range paper punchers like 6mm ppc. What makes the biggest difference, effectively IMO, is bullet construction. The larger the diameter the bullet, the more the slightest difference in concentricity leads to inaccuracies. This is why .224 is more accurate on average than .338. The farther that imperfection is from the center of the bullet and the more the lead insides make up a percentage of the bullet over the jacket, the more perfect a bullet must be to be consistent. Think about a bullet spinning at 200,000 rpm with just that tad of imperfection off of the centerline and how that may affect balance and bullet flight.

Sorry, I miss read the OP... I thought he said inherently INaccaurate.
Someotherguy has a good answer.
.25-06 is thought of as an accurate round where .270 not as much. Why? Same case...

You've got this backwards. Small imperfections are magnified in small bullets. Big bores are known for accuracy.

[Krazykarl]

Like previously mentioned, the assumption that short cartridges are increasingly accurate over the same bore size larger capacity case relies upon powder ignition. The primer shock wave, gases, and products of combustion in the shorter case results in more complete combustion of powder. In fact, there was some experimentation done where primers with extended flash tubes were created. This was an attempt to fully incorporate the larger powder charge of a larger case. The concept was only useful in very large cases like the US Army experiments with 105mm.