...right, and this is why I don't understand why ball ammo doesn't have a reputation for accuracy.
Ball ammo’s made with material with loose specs for uniformity. It has to work to an acceptable level in the worst of combat environments. Which is why military ball ammo bullet diameters are smaller than the rifle barrel’s smallest groove diameters so barrels in worst condition, wear or fouled, would still shoot good enough for combat use. It’s got heavily crimped in bullets so OAL specs are met for reliable operation in autoloading weapons, powerful but not too uniform primers, bullets unbalanced to some degree but durable in handling, 60 to 70 fps spread in muzzle velocity and case necks not to straight overall on case shoulders. And their quite out of square case heads make barrels point at all the numbers on the clock when the bullets leave; mostly right angles to the bolt locking lug axis. All devastating for best accuracy.
It's like picking the best tool to use for chopping down a tree and brain surgery when the only two tools available are an axe and scalpel.
That said, Lake City arsenal’s lot 12638 of M80 ball ammo made with IMR4475 powder and bullets miking .3078" diameter shot almost as accurate as their M118 match ammo thru 300 yards with bullets miking .3085" diameter in the USN Garand barrels whose groove diameter was also .3078". Those barrels were selected from a few hundred made by Springfield Armory in MA air gauging them for groove uniformity. All those .3078" uniform and smaller were set aside for match grade Garands. The others gauging up to .3085" were set aside for normal service use at Recruit Training Commands. Such is life when a rifling broach is used to cut the grooves in several barrels before it gets worn out. Barrels made at the end of the broach life were the most accurate.
Radway Arsenal in Great Britain made M80 ammo for the Kindom’s Fullbore long range rifle matches shot from 300 to 1000 yards. Their rules required issued arsenal ammo be used by all competitors; no handloads allowed. They used to issue rifles to everyone based on their belief that that would “level the playing field” and the best shot would win the match. That stopped in the 1960s when they used 7.62 NATO ammo instead of .303 British in their SMLE’s as well as Mauser 98 type bolt action rifles after realizing that all rifles of the same make and model don’t shoot the same accuracy wise. Their 7.62 NATO M80 bullets were often .307" diameter and barrel makers made the groove diameters .3065" so best accuracy was at hand. Best lots of Radway arsenal M80 ammo would shoot MOA through 300 yards and about 2 MOA at 1000. When Great Britain and its Commonwealth countries allowed the Swing 4-lug bolt action to be used, Radway M80 ball ammo shot even more accurate; it was the best thing going for out of square case heads; nobody was allowed to use reloads with very square once fired cases with squared up heads.
With a closed tip even a thick jacket made of a hard enough alloy can be made highly accurate with enough pressure, right?
Nope.
The most uniform jackets in bullets are made with the thinnest jacket material. It’s easier to shape to uniform dimensions than thicker stuff. All of which is why match bullets usually have thinner jackets than hunting or military bullets.
Yes, good FMJBT match bullets can be made. Sierra and Western Cartridge Company made very accurate ones up through 1958 and were favored by all the 30 caliber match rifle shooters to produce the best scores. Western Cartridge Company used FMJBT 200-gr. match bullets in their 1958 lot of ammo made for the US Olympic Teams 300 metre free rifles; .3088" diameter. They shot very accurate in Winchester 70 broach rifled match barrels with .3085" groove diameter. Two years later and benefitting from Sierra’s very accurate 168-gr. International 30 caliber hollow point match bullet, WCC60 match ammo made for the US teams were 190-gr. BTHP bullets made with precision dies like those used to make their Open Point Expanding hunting bullets. The label on the white boxes holding them said ‘197 grain OPE Bullet.” They also shot very nice in those same barrels. A .30-06 shooting reduced loads with these 197's won the Palma Match at the Nationals in the late 1980's. I’ve shot several of each in post '64 Win 70 hammer forged match barrels about MOA at a thousand yards. Norma 139-gr. FMJBT 6.5mm nickel plated match bullets were favored by 300 meter biathlon and Olympic competitors shooting the 6.5 Swede round for years before Sierra’s 308 168's hit the market.
Lapua has also made their 30 caliber D46 185-gr. FMJ rebated hollow base match bullet very precisely. A friend shot a few dozen of them from the same lot at 600 yards getting 10-shot groups all under 1.5 inches with a couple as small as .7 inch. Then put 40 of ‘em inside 1.92 inch. (For all the big, round heavy single shot action aficionados: He used a box magazine pre '64 Win 70 action, Hart barrel, wood stock and full length sized cases.)