My Alfa was supplied with two piercing caps and one of them very occasionally does not pierce the bulb cleanly. If the gun is new, get the cap changed by the retailer/importer. If an old gun, drop in a suitable sized washer, about 1 or 2mm thick, before the bulb. It won't do any harm and is the same principle as using the 8 gram adaptor for small Sparklet bulbs. It's just a case of lifting the bulb a mm or two.
Walther CP-2 Match, FAS 604 & Tau 7 target pistols, Smith & Wesson 6" & 4" co2 pistol, Crosman 1377,
Baikal IZH 53 pistol, Gamo CFX Royal,177, Umarex SA-10 CO2 pistol.