I've ran 50 TNTs to 3500 fps in a 223 with a 1 in 12 and a 1 in 9 twist, with only a few turning into a "puff" a foot or two out of the barrel...

long ago talking to a Speer Manufacturing manager, he told me that they figure the TNT is good to 3500 fps....and list it lower, because plenty of people would see how much past that they would push it... so they instead list it publicly around 3300 fps...

I've had them hold up to 3700 fps in a one in 12 twist......but I'll concede that wasn't in a consistent basis...

I test stuff like that in my spare time....

"Minus the killings, Washington has one of the lowest crime rates in the Country" Marion Barry, Mayor of Wash DC

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