If you REALLY want to know, just get a piece of polycarb at a local store, a cheap plastic seringe with cc's, and some rubbing alcohol, and some grease. All stuff very easy to find. First cut the plastic round, JUST smaller than the bore. Deburr it good. Place it on the piston and mark a spot at the very top of the dish. (It's clear, you can see through it) Take it out and drill a very small hole in it. Then take the grease and put just around the dish - Just enough to seal the piston to the plastic. You will actually be able to see the grease sealing as you press it on to the piston, so just look all the way around the dish to see if it sealed. Take your seringe and put whatever it has for cc's in of the alcohol. Keep filling it up, noting how many cc's you are putting in. Now this is NOT a perfect scenario, but you will be within one or at the very most 2 cc's of actual. THIS will tell you. Done.