help with military medal enquiries

[thunderboltflyer]

Good evening all.
I am looking for assistance or guidance in finding out more about my grandfathers Military Medal and the circumstances of him winning it.. The family say that he rarely talked about his experiences and no one else is alive to ask for more details. Family history recounts that he won it by swimming a canal with a machine gun on his back and silencing the enemy, but we don't know how accurate this is, where/when the action occurred as we have no paperwork with the medal.
Do medal awards come with details of the deed which earned it and can they be found recorded anywhere ? I have found his listing in the London Gazette dated 23rd July 1919 on page 9373. I have tried the National Archive website but cannot find him listed there but other copies of medal index cards dont seem to list the deed, only basic information so i don't know if this would help.
His name was Jack Beasant from Swindon and he was a corporal in 8th Worcester's. The inscription on the rim of the medal is 51028 Cpl J Beasant 8 Worcester.
Any assistance would be gratefully received
Richard