Is the cap on the lower front portion of the MR1 receiver removable?
This is the cap right below the barrel, which on most Spyders can be removed (unscrewed) and replaced by a volumizer, low-pressure chamber, or other air accessory, e.g., a mil-sim under-barrel grenade launcher that uses a common air source with the marker.
http://www.addictedtopaintball.com/s..._10304621.html
If someone could let me know definitively if you can unscrew this cap on an MR1 to install upgrades, I'd be grateful.