115 DTACs in a 6CM gas gun?

That depends more on your barrel's twist rate than velocity. Temperature, pressure, and altitude will also play a role. A barrel twist of 1:7, yes, 1:7.7 likely, 1:8 possibly. Slower than that and you might start seeing issues. minor changes in velocity won't have a large affect. 2890 vs. 2920 vs. 2950 will have a very small impact on stability.
 
That depends more on your barrel's twist rate than velocity. Temperature, pressure, and altitude will also play a role. A barrel twist of 1:7, yes, 1:7.7 likely, 1:8 possibly. Slower than that and you might start seeing issues. minor changes in velocity won't have a large affect. 2890 vs. 2920 vs. 2950 will have a very small impact on stability.

Thanks for that it's a 7.7 twist.
 
You’re good with a 7.7. On a very cold day with high pressure, at or below sea level you could see sub-optimal stabilization.
It would be hard to find conditions in which the bullet would actually tumble.