BONE STOCK 1377c CHRONY RESULTS!

[Supercharged86]

Hey Guys, as I wait for the upgrade parts from Mellon to arrive I thought I get some baseline chrony results using a selection of light pellets I have on hand.  I found a few things interesting: the first was the extreme spread on the GAMO PBA, although, being just one low shot, I would be more inclined to throw that one out and average it again.  The second was the results for the JSB's, being slightly higher than the CP SuperMatch, perhaps the domed head of the JSB'S resulting in slightly higher speeds than the flat head's of the CP match.  Can't wait for the new parts to arrive.  Cheers.  Steve

 

[quickster47 †]

Good stuff Steve.  It is always good to get a baseline before one starts getting too deep into the modifications.

Carl

[1377x]

good job!
cant wait to see the modded numbers

[Cross Pistol Packer]

Good to take stock results first to see later modded improvment of fps.
All at 10 pumps I take it?
Ray..

[Supercharged86]

Thanks guys.  Are they're any other light pellets that I should consider before pulling this thing apart?  Cheers.  Steve

[quickster47 †]

I was thinking about the Prometheus ThUnder BOLT Pellets weighing 5 grains but then I realized you used some Gamo 5.4 grain pellets and think there would not be too much difference.

Carl

[1377x]

Thanks guys.  Are they're any other light pellets that I should consider before pulling this thing apart?  Cheers.  Steve

no but did you do 1 pump,2 pump,3 pump etc  fps test

[Supercharged86]

no but did you do 1 pump,2 pump,3 pump etc  fps test

Yes, so far I've done this with the JSB Exact Diabolo 8.4 grn http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=2522.msg40353#msg40353 and plan on doing it with the RWS H-Point 6.9 grn.

[Supercharged86]

Hey Guys,  So the new parts from Charlie have arrived and the first order of business was to redo the chrony tests with just the new 12" barrel.  Since most of it needed to come apart I figured I'd install the solid pin to make things easier afterwards.  So after installing the new barrel with fiber optic sight, the 2289 barrel band and the solid pin kit I realized there was a small problem, perhaps you guys have come across this already and if so I apologize for the repeat.  As it turns out the 2289 barrel band is slightly longer, perhaps about 3/16" or so and unfortunately, the pumper handle hits the end of the band when fully opened.  This in turn keeps the piston from fully retracting as I noticed there is no longer a small gap at the front of the piston seal cup.  Since I won't be replacing the grips and pumper arm right now I'll have to clearance the front of the pumper arm to clear the band.  No big deal I guess.  I did run a few shots over the chrony and it would appear that the extra two inches of barrel are worth about 5 fps.  Perhaps after the pumper arm is clearanced and piston is allowed to fully retract, there will be a fewmore fps in there.  If not, hopefully the extra two inches will provide some additional accuracy.  I'll get the rest of the parts installed soon and will report back.  Thanks.  Steve

[Daysailer]

Yes, so far I've done this with the JSB Exact Diabolo 8.4 grn http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=2522.msg40353#msg40353 and plan on doing it with the RWS H-Point 6.9 grn.

Supercharge.... I checked out your string of 2 pump, 3 pump...etc and studied the #7 issue.
I have been doing many many of these cascading pump power test lately and I am pretty
sure that your #7 was really a 6 pump reading.  I sometimes have miscounted and had
the same thing happen.  If you look at your results, you will see as  the pump count goes
up, the increase per pump goes down....  ie,  my most recent moded 1377 test pump 5 to 6
increased 25 fps, and the 7 to 8 increased 16.



In my recent experiences the 1377 is very stable from brand new to broken in.   And then
from newly moded to 500 shots later, unless something breaks. 5 shot averages rarely
show more than 5-10 fps differences for a given day.  Even if you run a higher  shot count average,
unless you sort weight and head and skirt sizes,  that spread will be pretty consisant.
The biggest day to day differences were traced to lubrication levels...that is, newly oiled
piston, higher fps and 100 or more shots later, off about 10 to 15 fps at each pump level.

Good luck with your mods.   Look forward to seeing the 3 to 5 pump fps results.

[1377x]

pump arm touching the barrel band not good
either get a 2289 pump arm or work your stock one down

[Supercharged86]

pump arm touching the barrel band not good
either get a 2289 pump arm or work your stock one down

Yeah, that's what I figured, so I'll just mod the front of the arm.   Steve