Posted 23 May 2010 - 12:55 PM
Okay, if it takes 2-3 strokes to get the dart out, I'd also check the barrel length. There's no magic forumla - it depends on the barrel material, the difference in diameter between the barrel and the dart (as you said, Home Depot foam is a little wider than Ace foam.) Different barrels have different amounts of friction, which could affect your performance.
(Apologies the barrel material and length is in the .FLV, but PhotoBucket is being a pain. Clicking on the link gives only a "The action that you were trying to perform has failed.")
Something I noticed is that some FBR seems to be almost smoothed on the surface. This could be from the heating (tumbling in the dryer or using the hair dryer). I'm not sure - I'm very new to making my own stefans, so I've not had a chance to see what happens to the foam under prolonged heat exposure. (I'm sure it's not going to be pretty, but it's worth trying.) The reason for mentioning this is because, for the sample stefans where the surface is 'sealed', it felt smoother, which could affect the whole coefficient of friction thing.
If you have the blaster open, work the piston once or twice - do you need to lube it? Plug the breech temporarily (with a finger, say) and work the piston. Can you? How much resistance? Ideally, with a plugged breech, you shouldn't be able to advance the piston. If you do the piston seal needs work.
This being a Longshot, the bolt head could be another source of leakage. If you can advance the piston while the breech is plugged, which way is the air escaping? Maybe hold it underwater, if you can't feel it blow against bare skin. If it's advancing around the breech, then the bolt head isn't sealing against the front of the piston.
Fugly is a feature.