Barrel length questions.

[WSAR15]

I am seeing more and more short 6.5G barrels - 10" or so.
I am wondering if the 6.5G behaves like the 223 and becomes a very loud dragon breath at each shot.
The 223 was optimized for powder burn in 20" barrels. What barrel length was the 6.5G round optimized for? It seems that 18"/20"" are well performing.
Thanks

[Bigs28]

Kinda depends on what optimized means to you. The perfect barrel length for me is around 12". It's short, liteweight, shoots sub moa, and lethal out too 300+ for hunting.

Someone else might have different needs.

[FRB6.5]

They are loud to bystanders like any short barrel, but the 12" guns are interesting to say the least.
Play with the calculator here https://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
123 gr ELD-M run 2234 fps for me.

R-MIL Rugged 1-824 Shepherd.jpg
1-8x 100 yard zero and can hold over to 800 with 10 mph wind without dialing, that's kind of exciting for a "pistol".

[WSAR15]

By optimized I meant the barrel length in which the powder burns out most efficiently before the bullet exits the barrel. The original 55gr 5.56mm by Stoner was 20".

[LRRPF52]

By optimized I meant the barrel length in which the powder burns out most efficiently before the bullet exits the barrel. The original 55gr 5.56mm by Stoner was 20".

The powder is burned in both of them within the first few inches.

With the SCHV rifle, a minority in Army Ordnance wanted as fast of a muzzle velocity as they could get in order to defeat a steel helmet with full perforation at 500yds. Powder burn for barrel length was not something they focused on at all. Original prototype rifles had a 22" barrel, which was later shortened to 20".

With 6.5 Grendel, the unsuppressed 12" does not sound that loud to me at all compared to a 16".

I would have to meter it to give exact db, but it's not too bad really, not like a 10.3" 5.56 NATO.