A gunsmith can help you.
700-1000
You can go to Browning.com and download a BAR manual.
Best to ask a gunsmith for help.
Check the receiver carefully.
Contact Browning Customer Service, and request an owner's manual for your rifle. You WILL need the pictures in it.
What do you want to know?
500 USD
100-1000+ depending on specifics
50-500 USD or more
DO NOT ATTEMPT THIS!!!!!!!!!!!!!!!! Send it back to Browning.
You will have to take it to a gunsmith to be measured. All are different.
Best to ask a gunsmith for assistance.