It varies. Mine was consistant but I would only get 4 to 5 mags before the pressure dropped the reg. I had a Ratworks conversion and new cylonder. I have 9 14 shot mags and I can use all of them and still have puff left.
Mine pre ratworks is probably worst case. It was serviced by an expert who tirned out to be a conman so maybe that affected my gun.
Anyhow, depends on use. How many targets do you want to shoot and how many rabbits you wanna carry.
You can look at a reg conversion or go Dr Bob buddy bottle conversion too