1377 Flat Top Valve/Cylinder Chrono Data?

[WaltWhite]

I'm trying to find chrono data per pump 2-10 pumps for a Crosman 1377 with flat top valve and cylinder.  Best I can come up with is from a guy a few years ago who did stuffed piston, shimmed cup and shaved valve but I'm not sure those numbers are directly applicable.  If anyone has a link, etc, it's greatly appreciated.

[breakfastchef]

Due to differences in manufacturing tolerances, changes in pellet lots, barrel bore variations, and general environmental factors, it is possible that your results will not closely mimic past results from someone else. My personal experience is that a 1377 with a stock length barrel, a flat top valve, and properly adjusted flat top piston will produce a pellet velocity increase of 50-100 fps at 10 pumps.

[DBOdude]

FWIU ....... using a 24 inch barrel rather than the stock 10 incher adds around 100ish FPS with 10 or more pumps . so consider barrel lengths used when comparing results .

[hstedman]

Walt...
I have a chrony and I'm planning on getting a flat top valve and piston from accustoms soon, i can post the before and after results on here if you'd like.

[DBOdude]

awesome hstedman !

i have AC's valve and standard piston so i'm looking forward to reading your results . let us know what caliber and length barrel you're using on your 13xx , type of bolt and other mods please .

[South Bay Dave]

I am also quite interested in those results as that's the same as the next upgrade I'm planning (Blue Fork Designs 13xx Pump Arm Pivot & Barrel band presently in transit) 
I'm also trying to modify some Uncle Mike's quick detachable super swivels

[ceejay]

A while back - couple years? - my new 1377 was 'projecting' 7.8g lead at 500fps with ten pumps.
Mellon piston and valve brought it up to 620fps.
.040 hammer spring gained another 40, up to 660 - all with stock barrel.
FWIW - the new spring would cleanly dump 15 pumps at 685fps, a walloping 8.1fpe  !!

[sshewins]

Ceejay,  what exactly do you mean by a .040 hammer spring? Look for them at a hardware store? Is the .040 referring to the thickness of the actual wire?

[ped]

don't know if this will help you but some chrono data from my back packer and my 760 tubed 1322 hybryd both are .22 with 14" barrels
2289
http://www.chartgo.com/create.do?chart=line&width=900&height=300&orientation=vertical&title=2289&subtitle=&xtitle=shot&ytitle=fps&source=&fonttypetitle=bold&fonttypelabel=normal&labelorientation=horizontal&chrtbkgndcolor=gradientblue&max_yaxis=640.0&transparency=1&labels=1&min_yaxis=100.0&roundedge=1&shadow=1&border=1&xaxis1=3%0D%0A4%0D%0A5%0D%0A6%0D%0A7%0D%0A8%0D%0A9%0D%0A10%0D%0A11%0D%0A12%0D%0A13%0D%0A14%0D%0A15%0D%0A16%0D%0A17%0D%0A18%0D%0A19%0D%0A20%0D%0A21%0D%0A22%0D%0A23%0D%0A24%0D%0A25%0D%0A26%0D%0A27%0D%0A28%0D%0A29%0D%0A30%0D%0A31%0D%0A32%0D%0A33%0D%0A34%0D%0A35%0D%0A36%0D%0A%0D%0A&yaxis1=335.4%0D%0A381.4%0D%0A426.3%0D%0A454.8%0D%0A485%0D%0A517.7%0D%0A543.2%0D%0A565.7%0D%0A583.7%0D%0A591.4%0D%0A584.3%0D%0A581.4%0D%0A567.2&group1=Group+1&yaxis2=%0D%0A%0D%0A100%0D%0A100%0D%0A100%0D%0A100%0D%0A100%0D%0A100%0D%0A100%0D%0A100%0D%0A179.8%0D%0A305.7%0D%0A388.5%0D%0A433.4%0D%0A479.2&group2=Group+2&add=&rem=&from=generaljsp&lang=en
hybryd
http://www.chartgo.com/create.do?chart=line&width=900&height=300&orientation=vertical&title=766%2F1322+hybryd&subtitle=&xtitle=shot&ytitle=fps&source=&fonttypetitle=bold&fonttypelabel=normal&labelorientation=horizontal&chrtbkgndcolor=gradientblue&max_yaxis=640.0&transparency=1&labels=1&min_yaxis=0.0&roundedge=1&shadow=1&border=1&xaxis1=3%0D%0A4%0D%0A5%0D%0A6%0D%0A7%0D%0A8%0D%0A9%0D%0A10%0D%0A11%0D%0A12%0D%0A13%0D%0A14%0D%0A15%0D%0A16%0D%0A17%0D%0A18%0D%0A19%0D%0A20%0D%0A21%0D%0A22%0D%0A23%0D%0A24%0D%0A25%0D%0A26%0D%0A27%0D%0A28%0D%0A29%0D%0A30%0D%0A31%0D%0A32%0D%0A33%0D%0A34%0D%0A35%0D%0A36%0D%0A%0D%0A&yaxis1=0%0D%0A&group1=&yaxis2=0%0D%0A&group2=&yaxis3=338.8%0D%0A388.6%0D%0A428.3%0D%0A454.5%0D%0A495.8%0D%0A519.3%0D%0A544.1%0D%0A573.8%0D%0A578.1%0D%0A593.7%0D%0A595.8%0D%0A611.6%0D%0A602.6&group3=Group+3&yaxis4=0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A60.8%0D%0A124.2%0D%0A192.2%0D%0A298.1%0D%0A361.9%0D%0A427.8&group4=Group+4&add=&rem=&from=generaljsp&lang=en#
both guns start retaining air at 9-10 pumps which helps limit them to our limit
in theory the longer tube should give better performance but the have different types of valves the backpacker has the earlier brass valve and the hybryd an ally one with a rear cocking hammer instead of a std weight hammer thats in the backpacker
this last graph shows the two together
http://www.chartgo.com/create.do?chart=line&width=900&height=300&orientation=vertical&title=2289v766%2F1322+hybred&subtitle=&xtitle=shot&ytitle=fps&source=&fonttypetitle=bold&fonttypelabel=normal&labelorientation=horizontal&chrtbkgndcolor=gradientblue&max_yaxis=640.0&transparency=1&labels=1&min_yaxis=0.0&roundedge=1&shadow=1&border=1&xaxis1=3%0D%0A4%0D%0A5%0D%0A6%0D%0A7%0D%0A8%0D%0A9%0D%0A10%0D%0A11%0D%0A12%0D%0A13%0D%0A14%0D%0A15%0D%0A16%0D%0A17%0D%0A18%0D%0A19%0D%0A20%0D%0A21%0D%0A22%0D%0A23%0D%0A24%0D%0A25%0D%0A26%0D%0A27%0D%0A28%0D%0A29%0D%0A30%0D%0A31%0D%0A32%0D%0A33%0D%0A34%0D%0A35%0D%0A36%0D%0A%0D%0A&yaxis1=335.4%0D%0A381.4%0D%0A426.3%0D%0A454.8%0D%0A485%0D%0A517.7%0D%0A543.2%0D%0A565.7%0D%0A583.7%0D%0A591.4%0D%0A584.3%0D%0A581.4%0D%0A567.2&group1=Group+1&yaxis2=0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A179.8%0D%0A305.7%0D%0A388.5%0D%0A433.4%0D%0A479.2&group2=Group+2&yaxis3=338.8%0D%0A388.6%0D%0A428.3%0D%0A454.5%0D%0A495.8%0D%0A519.3%0D%0A544.1%0D%0A573.8%0D%0A578.1%0D%0A593.7%0D%0A595.8%0D%0A611.6%0D%0A602.6&group3=Group+3&yaxis4=0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A0%0D%0A60.8%0D%0A124.2%0D%0A192.2%0D%0A298.1%0D%0A361.9%0D%0A427.8&group4=Group+4&add=&rem=&from=generaljsp&lang=en
hope this helps you
ped

[ceejay]

Ceejay,  what exactly do you mean by a .040 hammer spring? Look for them at a hardware store? Is the .040 referring to the thickness of the actual wire?

(Yes, to both)

[sshewins]

Cool, thanks