So I jumped in the 338 sub calibers, and here's what I found.
I've had both 3 twist and 6.5 twist in 8.6...the 3 twist was horrible it was one of the first Faxon barrels, complete with torn rifling.
The max pressure is reached in the 3 twist long before what can be done in the 6.5 twist, like 2.5 gr to 3 gr less powder.
And only copper bullets are deemed safe at supersonic speeds. But any cheap lead bullet will go as fast as you can drive it it the 6.5 twist plus 350 gr Maker subs are not limited to 1000 to 1050 fps, as in the 3 twist before disintegration, but instead I shot them to 1670 fps in the 6.5 twist, with no ill effect in the 8.6 making it a true dual purpose cartridge like 200 gr Speers at almost 2600 fps in a long barreled bolt.
The 6.5 twist was custom order and put in a bolt gun, much better, accurate, fast, and very capable.
Then the 338 ARC came out, a better option for subs...except nothing available but Hornady propaganda.
So I bought the 338 Spectre in AR 15 barrel since they are very close to the 338 ARC...it has a 6.5 twist, which Maker makes a variety of bullets for 125 gr solid, 165 gr super expanding, several in the 210 to 225 gr range and a 300 gr specifically for the 6.5 twist. I even shot the 350 gr maker in the 338 Spectre...but that's a lot of bullet for a tiny case.
Accuracy is very good, clean combustion with most powders as case fill and higher pressure result in lower S/D s and better accuracy.
Everything is available for the 338 Spectre, bullets, brass, and AR 15 barrels,...don't know about bolt guns on this cartridge as I wanted the AR platform plus it has a 6.5 twist barrel and is very accurate with 300 gr SMK and 300 Maker bullets.
I fired a few 350 gr at 880 fps with accuracy but probably won't make 1000 fps without pressure.
Maker has a few bullets for the 3 twist much more for the 6.5 twist, and none for Hornadys new 8 twist...yet,...but if it becomes popular they most likely will.
The 8.6 with a 6.5 twist is a true dual purpose cartridge, but tends to struggle with sub accuracy and consistency.
The 338 Spectre is great for subs but struggles with high enough velocity for most conventional bullets for hunting.
But Maker has a 165 gr super expanding bullet for the 338 Spectre that I ran at 2100 fps and it supposed expand at 900 fps but that would have to be tested.
