New 1377 Power output?

[brz-ryder †]

You guys do realize that the numbers that they state for top fps is using the lead free ssp pellets don`t you these pellets only go 4 gr in .177 and 9.5 gr in .22 this is why the numbers are so high

Jim

[Crosshairs]

with 10 pumps?

Yes 10 pumps.

[Trophyhunter49]

You guys do realize that the numbers that they state for top fps is using the lead free ssp pellets don`t you these pellets only go 4 gr in .177 and 9.5 gr in .22 this is why the numbers are so high

Jim

Yes Sir  it all sounds good on paper. Makes for more sales that way LOL

[jSan22]

yep. and most of those high velocity pellets are crap. either they are too soft and spray like a SNS pistol that desperately needs cleaning, plus end up being like throwing tissue at the target, or too hard and do not engage the rifling correctly and not only get part of the above result, but over penetrate and fail to kill if its anything but a head shot.
i once shot a squirrel with those 4 grain crosman ss "hollow point" (more like a wadcutter with a tiny dent in it) and he was barel effected with it. this was with a stock crosman 1377 that usually flipped the bastards with one shot from a 7.4 grain pellet.
im still searching for that one lead free that DOESNT suck.

[ettolo]

Hi,
anyone knows how the power limitation in 1377 is done for UK or Italy?
I know of different TP inner diameter, but there is something else?
Different spring in the valve?

[rangerfredbob]

There's either a hole in the rear of the valve housing, or a bigger squared out exhaust valve stem is installed to let some of the air out the back of the valve instead of through the transfer port.

[ettolo]

There's either a hole in the rear of the valve housing, or a bigger squared out exhaust valve stem is installed to let some of the air out the back of the valve instead of through the transfer port.

Thanks!

[Noah]

Not to hijack this thread, but does anybody have or have shot a 1325 with all the internal modifications (FT piston, etc.)? I'm curious why mine suddenly shoots only 400 fps with 20.06 field target trophy pellets when it used to reach as high as 510ish or so. Hmmm. See below (the one with RB's red and black grips).

[jSan22]

510 with 20 grain pellets is good. it may be a bad seal.

[WyoMan]

Not to hijack this thread, but does anybody have or have shot a 1325 with all the internal modifications (FT piston, etc.)? I'm curious why mine suddenly shoots only 400 fps with 20.06 field target trophy pellets when it used to reach as high as 510ish or so. Hmmm. See below (the one with RB's red and black grips).

Hi Noah, was going to answer here but I started a new topic in the tech section:
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,13024.0.html

[BDS]

Nice work on that thread Wyo, I'm sure that lot's of folks might think that a Chrono actually measures "speed" when it actually measures time between sensors calculated as speed 

[WyoMan]

Thanks Brian...that problem got me once and I wanted to shoot the stupid chrony...with a 350M...loaded with Gamo Rocket 9.6 gr ballistic tip 

[K.O.]

My time of flight chrono method (pc/audacity/2mics/15') clocked my  PC77 at 530 fps average velocity over 15'.   That was with 7.4g Crosman points seated with a simple tool just past the port, unseated velocity was about 508 fps. This was at 10 pumps and additional pumps offered no gains.

I think if I had just fitted the pump cup and valve to each other and shimmed the cup to get 0 headspace I would have seen 540-545 fps and might

have achieved more with additional pumps...

[Hung2]

Excuse me, I am not trying to hijack or question the wisdom of other posters, but my desire for a succinct understanding of the logic urges me to ask.

1)If closing up the little head space between the valve top and the pump cut would increase x #  of fps, wouldn't the head space loss over the 10 pumps be fully made up by an additional full-stroke pump on top of the 10?

2)Again, a flat-top eliminates the head space wasted by a coned valve top. Wouldn't two more full-stroke pumps in addition to the 10 make up for the head space loss in a coned piston?

I can certainly see the logic in pushing the pellet well past the transfer port. I don't have an extended bolt probe, but I use an a L shaped tool to push it in anyway.

[WyoMan]

Reasonable questions H2...
it depends for both #1 and #2...
Additional pumps will be a benefit only if: (pump pressure - checkvalve cracking pressure) > valve pressure
A good way to optimize a pumper is to optimize the pump pressure...take as much swept volume as possible and compress it into the smallest space possible (with no leaks)
This will create the most pressure possible (provided the strength of the pump mechanism is not exceeded)...another advantage of the FT system is you have a more rigid piston than the oem...but it can also overstress the other parts of the system
i.e. valve being forced toward the back, ovaling of the pivot hole, excessive wear on the pins, lever and connector, etc...hth