..but I owe someone some real-world bulk fill numbers.
Pretty much a standard QB78. Did shorten the barrel greatly (down to 16â€), smooth the rough areas inside, and put in a poly-port. This rifle is NOT tuned fast. I worked pretty hard getting it to run well at the low speeds i wanted for back yard bird killing (with a 25-40 yard max. backyard range).
On 12gr., would get 552fps/14.5gr. pellets. Getting 45 good shots per fill before measured vel. drop off.
Without creating a big temperature difference between the bulk fill tank and the rifle, will take in 1.1oz. of co2. Did leave the bulk tank in the shop for 1/2 an hour (at 83 degrees) and the rifle inside the house (at 75 degrees) so there was a little temp difference.
Got 45 shots again before measuring a vel. drop off. Was still 1/10th ounce (about 3gr.) of co2 in the tube, but it was all gas...no liquid...so vel. would drop with each shot (about 8 more every slower shots).
Vel. went up about 28fps with bull fill to 578fps.
SO...yes, bulk fill does give a bit more speed, even with a standard valve. Suspect that when using 12gr., the piercing pin uses the 12gr. cartridge as a ‘stopâ€...valve can’t open any farther than contact by the piercing stem). Even with the same valve, if there is no “stop†the valve tends to open farther and the gas to flow a little smoother.
Nothing is for free, and that little extra speed costs a little extra gas on each shot.
(With 12gr., would use about 22 -23 of co2 before vel. drop off to get 45 shots. With bulk fill, would use about 25-26 gr. for the same number of good shots.)
