Colonial musket barrel .50 cal. Any info?

[XtreasureX]

I found this barrel a few years ago at an old colonial site in northern Mexico. It is bronze, seven inches long, and .50 caliber. There are markings on the end of what is the bottom of the barrel. There is another mark under the oxidized iron where the barrel was mounted that I can't really read . I haven't been able to find any info about this online. I was hoping someone would be able to ID it.

 

[HuntinDog]

Are you sure that the proof mark is an M?
Could it be a W?

 

[NOLA_Ken]

If you have a dremel tool you could use one of the small sanding drums to clean up the deformed part of the muzzle and get it back to the original bore diameter.