Mossberg M500 Muzzle-loading barrel questions...

[jjrothWA]

Just picked up a m500 ML barrel, figured out the procedure for detailing the spring-loaded primer extractor, but does the barrel plug unscrew to detail the barrel and plug or is the barrel machoined from a single blank?

Did a test fire in garage with a W209, but lot of leeakage frpm [primer, is that due to the small neck of the W209 and to minimize use a constant diameter 209 equivalent primer?

thanks.

[Sunray]

There's a really good line drawing of the barrel and its threaded plug. And a 'not bad' one of the priming. Says to use a #209 shotgun primer. There are some loads too.
http://www.mossberg.com/wp-content/uploads/2015/04/500-12-gauge-Muzzleloader.pdf