should be noted that a conventional firing unit not shown fires each paint ball 60 from the barrel ba of the gun g toward an intended target also not shown the firing unit uses compressed gas to fire each paint ball 60 before a paint ball 60 is fired the plug 50 must be located at the first position shown in fig1 the moment the firing unit fires the paint ball 60 the retraction of the bolt bo shown in fig4 of the firing unit creates the back pressure and the external air is sucked into the firing chamber 40 through the bore of the barrel ba the external air applies compressed pressure to the firing chamber 40 in the radial direction r consequently the lowermost paint ball 60a which is the next paint ball to be loaded is compressed toward the guide surface 52 however since the plug 50 partially seals the fourth opening 38 the lowermost paint ball 60a is prevented from passing therethrough the compressed air is released from the unsealed fourth opening 38 to the outside then the lowermost paint ball 60a drops to be loaded into the barrel ba via the first opening 12 in the firing chamber 10 the first opening 42 in the collar 40 and the third opening 36 in the magazine 30 the firing chamber 10 may have a second opening 14 and the collar 40 may have a second opening 44 corresponding to the second opening 14 in the firing chamber 10 as shown in fig2 these openings 14 44 would provide supplemental relief of the back pressure produced by the bolt bo action during this loading procedure the compressed air created by the back pressure does not affect the rest of the paint.