I think he means theory, where "over stabilized" bullet does not follow tangent of the trajectory, but flies a bit "nose up" resulting in lower BC, larger drift etc. IIRC this theory is debunked, but cannot remember for sure. Anyway only relevant at distances 500-600 meters plus.
Yes, you're correct. Bryan Litz amongst others has shown how this old theory is quite incorrect.
The original reason for using the absolutely lowest twist rate that barely stabilised the bullet was poor quality out of balance projectiles. The faster they were spun, the more they deviated in flight especially at longer distances. The ultimate in this regard (I among others would say 'nadir') was GB NRA 'Target Rifle' from its inception in 1968 to the 1990s when the fixation with TR's past links to .303 Service Rifle saw mandated use of military-spec 7.62 FMJ ammunition whose bullets were so poor that a turn in 14-inches twist was the norm. (The cases were rubbish too, hence the 4-lug SWING/Paramount/RPA action, four equally space lugs giving best results with brass with out-of-square case-heads.)
Today, 10-twist is almost the 308 Win norm for long-range FTR-class with 9.5 and even 9 twists also used (long 200gn bullets). However, practical long-range work by Bryan Litz and the 185gn Berger Juggernaut suggests better long-range results might come from using 8-twist with the cartridge. (
Modern Advancements in Long-Range Shooting published by Applied Ballistics LLC can't remember which particular volume).
Litz and many other ballisticians now appear to be saying that in ballistic terms alone, you cannot over-spin modern bullets
provided their structural integrity isn't compromised (bullet blow-up). Back when I shot FTR at national level, I mostly shot Berger 155.5s in a 10-twist barrel. In UK conditions, this combination gives an Sg (coefficient of stability) of 2.31 where 1.5 is optimal. When I competed at Raton, New Mexico in 2013 at 7,500 ft ASL / 90s F temperatures, that rose to 3.25, this applying to most everyone in the 14-strong UK contingent, and a value that would have been regarded as massively too high not that many years before. Results were uniformly good in 800-1,000 yards competitions. (To get rid of our loaded ammunition before flying back, there was a final fun-session shooting first at a steel buffalo silhouette, then at ever smaller rocks at over 1,400 yards with astonishing results - also a tribute to the super-clear dry air in New Mexico and the resulting superb view through riflescopes.)
That's not to say that specialised competition applications should dictate practices in more common field and target situations, rather to show that the over-spinning bogeyman really doesn't apply and going for a tad faster twist rate than the norm is better (much better) than going for a tad slower, again with the proviso that it doesn't overstress some models of lightweight frangible varmint bullets.
