Best barrel length for AR pistols in various calibers?

[Rorge Retson]

I am sure this info is somewhere but I just can't seem to find it.

What are the ideal barrel lengths for the following AR pistol calibers?
- 5.56
- 6.5
- 6.8
- 300 AAC

I know there are ideal lengths for reasons, but I don't know what they are - stability? Noise? Flash? Any help appreciated.

[Sniper3142]

Best length for what?

- Ballistic Performance?
- Handling & Recoil?
- Noise & Flash?
- Function & Reliability?

[Rorge Retson]

In order of preference:
1) Ballistic Performance
2) Function & Reliability
3) Handling & Recoil
4) Noise & Flash

[Capybara]

My 11" barrel is great on ballistics, accuracy, reliability with 5.56. Handling is a bit ridiculous as my OAL is 28 and 1/4" making my "pistol" a Title I "other", not a pistol but I can have the VFG, which is cool. For all intents, it is an SBR-like gun without a butt stock. The combo of PG, VFG, cheek weld on buffer tube and a single point sling make it pretty steady to hold, although not as comfortable as a rifle, of course.

Have heard that the really short barrels are awful on rifle calibers (wasting most of your velocity, burning a lot of the extra powder, huge boom, but little recoil for the same reason an Obrez kicks much less than an M44. Short barrels are decent on pistol calibers, but I wouldn't go under 10" with the calibers you are talking about, just my opinion. Hope this helps.