I see a lot about the twist rate in terms of accuracy....sure, a stable bullet will squeeze out the most a system is capable of, accuracy-wise, but when you're talking about a 16 in. barrel, would not there be some advantage in having a round that is just waiting for an excuse to tumble like crazy? Never heard of any ballistic gelatin tests to confirm, but it seems the terminal ballistics of, say a 1:9 twist rate and a 62 gr. or heavier bullet would be pretty ferocious.
I see a lot about the twist rate in terms of accuracy....sure, a stable bullet will squeeze out the most a system is capable of, accuracy-wise, but when you're talking about a 16 in. barrel, would not there be some advantage in having a round that is just waiting for an excuse to tumble like crazy? Never heard of any ballistic gelatin tests to confirm, but it seems the terminal ballistics of, say a 1:9 twist rate and a 62 gr. or heavier bullet would be pretty ferocious.
You're quite correct. And the older M16A1 1:12 twist barrels are not only also better at stabilizing the 55-grain bullets of the older military M193 ball load, but also work MUCH better with the various .22 conversion kits if lead-bullet .22 long rifle ammo is used.
To summarize: get a 1:7 [or 1:8 match grade, if not using tracers] twist barrel if you plan on using the military M855 ammo [or Euro SS109] with a 62-grain or heavier bullet. Get a 1:12 M16A1 barrel for M193/ 55-grain or import equivalent, or for use with a .22 conversion. If you have a 1:9 *compromise* barrel and are having good luch with the ammo you're running through it, stick with that load.
And, in general, you want the longest barrel possible, at LEAST a 16 incher, preferably a 20-inch military-length rifle barrel- if you plan on getting both accuracy and bullet expansion on your intended targets.