Interesting that you put the washers between the O-rings. Your two washers equal the thickness of another o-ring.
Does Crosman offer a transfer port in the 0.094" size? I am not confident in my abilities to drill to that size myself. Also and further detail on the washers used would be appreciated.
Quote from: EMrider on April 05, 2015, 06:30:17 PMDoes Crosman offer a transfer port in the 0.094" size? I am not confident in my abilities to drill to that size myself. Also and further detail on the washers used would be appreciated. Hi Em, according to the information I found, Crosman supplies a 0.043" (red) and 0.065" (silver) transfer port with the 1720T. The one I was working with had the 0.065" and it is aluminum so it is super easy to drill out with a set of numbered drill bits. I just clamped it in my vise with wood jaws so as not to mar it, and drilled it with increasing sizes until hitting 0.094".If you can't find a way to get it done, PM me about sending one of the transfer ports and I'll do it for free.
Quote from: FuzzyGrub on April 05, 2015, 02:53:08 PMInteresting that you put the washers between the O-rings. Your two washers equal the thickness of another o-ring. Hi John, it appears the shot-to-shot consistency improved with the addition of the flat washers. The strings without the washers looked more jagged. I have a theory...when the O-rings are butted against each other, the contact patch between them is very small and the effective height of the stack may vary if they shift slightly relative to each other. Placing a washer between them gives them a flat surface to bear against, keeping the stack more consistent.Again, just a theory! I would need to run a controlled experiment to confirm.
I did not apply any grease to the O-rings. They seemed to hold snug to the walls. The hammer and inside walls are lubricated with graphite powder. I try to keep viscous materials out of that area.
Bumping this old thread to ask a couple questions about this specific set of mods.1) How hard is it to do these mods? (in terms of hours)1-2 hours going very slow for the first time. Tuning may take longer2) does the manual have a good exploded view that will make obvious (along with this thread) what to do?Not in the manual, but on crosman website has parts schematic.3) Where do I get those very specific parts? I could probably find the drill bit on ebay. (I only have fractional inch bits) but how about the O-rings and washers?Buy a bag of 100 of #113 70D buna-N O-rings. They are also used to rebuild your gun. The o-ring store or many other sources.Fractional drill 7/64" will do it.If going with a 15fpe tune, sub the two thin SS washers with a neoprene fender washer 3/4" OD, 0.070" thick, found at local H/W store. No need to grind to fit.4) How much louder is the 1720T than a .177 Marauder? How much more accurate is it?Stock form and power, probably close. At 15fpe, you might add a LDC. 5) You mentioned # of turns from full CCW. Doesn't full CCW make the screws fall out?No. Full CW does.6) Where does the Bstaley stack go?Between hammer and back of valve.7) Is the Bstaley stack sold as a kit, or assembled from parts bought elsewhere?Just buy a bag of the O-rings above and this spring: http://www.mcmaster.com/#9434k65/=14kjgy5 They also sell o-ringsSorry for all the dumb questions; I've never modded a PCP gun before.Search for "marauder pistol assembly". There is a good tutorial out there somewhere.Thanks!I modded my 1377 myself, with the flat top piston and power adjust mods, after finding some good instructions online.