What’s the difference between /ɒ/ and /ɑ/?

He nearly swallowed it.
(Harry Potter and the Sorcerer’s Stone)

Jim Dale’s audio
Stephen Fry’s audio

How does Jim Dale pronounce the a in swallowed: /ɒ/ or /ɑ/?
Considering his nationality, it seems more likely /ɒ/. But it doesn’t sound like how Stephen Fry pronounces. I want to know which one Jim Dale pronounces and what the difference between the two is.

Answer

I can’t actually hear any difference. To the extent that there is one, it’s regional variation in pronunciation of the same phoneme (ɒ as in hot, odd, wash). But OP might wish to note comment #3 here…

In AmE, ɑ: and ɒ are one vowel, so calm and cot have the same vowel. In American transcriptions, hot is written as hɑ:t

Attribution
Source : Link , Question Author : Listenever , Answer Author : FumbleFingers