Hi Guys,
Can you tell me what power you guys in the US are getting from a new and completely standard 1377 with ten pumps,
Thanks.
Well it's under 600 fps that's for sure, i'm getting 505 fps from one of my stock 1377s and that's good compared to some.
Mike
Quote from: Crosshairs on May 09, 2013, 02:02:48 PM
Well it's under 600 fps that's for sure, i'm getting 505 fps from one of my stock 1377s and that's good compared to some.
Mike
with 10 pumps?
With my '77 shooting Crosman Destroyers and only a ext probe bolt does high 500's witha peak of 589 and a low of 558 fps.
(http://img.photobucket.com/albums/v465/CWLONGSHOT/Temp%20stuff/sporting%20pics/Air%20guns/Crosman%201377/null_zps22e9cd11.jpg)
CW
This has been my experience with newer 1377 pistols at 10 pumps. Typically I have seen 500-520 fps. I had one shoot @550 fps at 10 pumps out of the package. These velocities were using my 7.0 grain test pellets.
Quote from: Crosshairs on May 09, 2013, 02:02:48 PM
Well it's under 600 fps that's for sure, i'm getting 505 fps from one of my stock 1377s and that's good compared to some.
Mike
Hi Guys,Thanks for your help :-* I have an old though new condition 1322 that easily is capable of the UK 6ftlb limit on air pistols and I wondered how close the 1377 may get to that limit in stock form.They seem as standard to be well short of 6ftlbs in the US and regadless imports for the UK market are knocked down even further in my experience.The 1377 has loads of potential of course and I shall buy one in the not too distant future for a little modding of course.
Hi CW,thanks for posting the pic' and the chrony numbers you have a nice looking pistol there. :)
Mark.
Mine is in the low 540's, but that was measured with the android app. The fps was pretty consistent between shots.
The "power mod" is a 12" barrel.
It's funny because they detune those guns they send America Jr. (Canada) and Britain, like the M4177. But mine is American and it chronied at like 495, eventhough the box states 600. So really they don't even need to detune them since the fps is already dreadfully lower than what they advertise.
I agree no need to detune further,but HM Customs are a hysterical bunch and I don't mean funny! ;D
530-ish fps with 8.0 g lead pellets at 8 pumps, gun is about 2 yrs old.
Quote from: mrto on May 09, 2013, 04:45:55 PM
Hi Guys,Thanks for your help :-* I have an old though new condition 1322 that easily is capable of the UK 6ftlb limit on air pistols and I wondered how close the 1377 may get to that limit in stock form.They seem as standard to be well short of 6ftlbs in the US and regadless im :-[ports for the UK market are knocked down even further in my experience.The 1377 has loads of potential of course and I shall buy one in the not too distant future for a little modding of course.
Hi CW,thanks for posting the pic' and the chrony numbers you have a nice looking pistol there. :)
Mark.
Thank you Mark!!
I have been reading that the Canada guns had a vent hole to bleed off some pressures. I also knew the UK had a limit, but did not know where that number fell.
I was quite pleased at my numbers! Now I do have a ext Probe bolt installed for those shots. I don't know what it did for the velocity, I am positive it increased it but by how much. 5 or 10fps? I would be very surprised if it was any more than that.
I started to install the failed flat top piston and valve. From last weekend. :-[. Then I will chrono it again and see.
CW
Quote from: agninja on May 09, 2013, 05:02:31 PM
It's funny because they detune those guns they send America Jr. (Canada) and Britain, like the M4177. But mine is American and it chronied at like 495, eventhough the box states 600. So really they don't even need to detune them since the fps is already dreadfully lower than what they advertise.
Funny! The blister of the one I bought here in italy say "495fps | 151mps max".
We have power limitation to 7,5j (for airguns and without a licence).
For a pellet weight of 0,53g our 1377 will go to only 6j :(
Saw photo of American (?) blister wich say 600fps max and other 625fps max
Quote from: Cwlongshot on May 09, 2013, 07:32:55 PM
Thank you Mark!!
I have been reading that the Canada guns had a vent hole to bleed off some pressures. I also knew the UK had a limit, but did not know where that number fell.
I was quite pleased at my numbers! Now I do have a ext Probe bolt installed for those shots. I don't know what it did for the velocity, I am positive it increased it but by how much. 5 or 10fps? I would be very surprised if it was any more than that.
I started to install the failed flat top piston and valve. From last weekend. :-[. Then I will chrono it again and see.
CW
Hi CW,
Yes,the UK power limit for pistols is 6ftlbs and for rifles 12ftlbs which as far as I know makes the British Isles the only country on the planet that has two different power limits for airguns on its statute books!!That said in both pistol and rifle useful trajectories can be achieved with the use of the correct pellet and sufficient power exists for vermin shooting.We in the UK do a little better generally speaking than our Canadian cousins in terms of permissable power limits as they are restricted to a maximum of 500fps I believe in both pistol or rifle and are not governed by a muzzle energy limitation.In .25 cal the Canadians do a little better than us in the UK.
I like the black grips and pump handle on the new 1377's as on your gun I much prefer them to the earlier brown grips etc that were fitted to this model.Good luck with your further modding by the way.
Mark.
The only 1377 that I have that is stock(all but the polish job) is my phase II. It chronys at 579 with 10 pumps and Crosman HP 7.9 pellets :)
Quote from: mrto on May 10, 2013, 12:32:36 PM
Hi CW,
Yes,the UK power limit for pistols is 6ftlbs and for rifles 12ftlbs which as far as I know makes the British Isles the only country on the planet that has two different power limits for airguns on its statute books!!That said in both pistol and rifle useful trajectories can be achieved with the use of the correct pellet and sufficient power exists for vermin shooting.We in the UK do a little better generally speaking than our Canadian cousins in terms of permissable power limits as they are restricted to a maximum of 500fps I believe in both pistol or rifle and are not governed by a muzzle energy limitation.In .25 cal the Canadians do a little better than us in the UK.
I like the black grips and pump handle on the new 1377's as on your gun I much prefer them to the earlier brown grips etc that were fitted to this model.Good luck with your further modding by the way.
Mark.
Thanks Mark,
Thanks for the clarifications. Sorry state regulating air guns...
CW
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
Quote from: brz-ryder on May 11, 2013, 12:51:16 AM
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
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.
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?
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.
Quote from: rangerfredbob on November 28, 2013, 02:42:39 AM
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!
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).
510 with 20 grain pellets is good. it may be a bad seal.
Quote from: Noah on November 28, 2013, 11:27:34 PM
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 (http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,13024.0.html)
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 :-*
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 :D
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...
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.
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
Thanks WyoM,
I am not an air-flow engineer and my curiosity has triggered all kind of logical questions.
Hi Hung2
I chose to keep the pump cup for WyoMan's reasons Durability and reliability.
Now about the more pumps thing yes you can pump more to make up for headspace but past a certain point the results can be erratic one shot will be 20-50 or so fps different at the same number of pumps than the next. That means one shot low the next high etc...
With my setup that is happening at about 20 pumps.
So I stop where my carbine is predictable... 17-18 pumps.
here is where headspace shows it self the valve holds .1 cubic inches of air = about 1.63 cc if I have .053 of headspace(=about .26cc) that makes it 16% bigger
or
If I take away the headspace then each pump will develop 16 % more pressure. ( http://en.wikipedia.org/wiki/Boyle%27s_law (http://en.wikipedia.org/wiki/Boyle%27s_law) )
Boyles Law is basically "At a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas."
which translates to double the volume half the pressure or increase volume by 16% decrease pressure by 16%...
Ok so I am pretty sure these things develop about 1000-1200 psi and that translates to having about 160 more psi if I am stopping at that level of predictable results...
17 pumps with headspace = 840 psi
17 pumps no headspace = 1000 psi
I do not think it is that simple in reality but is close enough to show the logic
I am one of those that believe the .177 pellet likes to be hit with as high velocity charge as possible so seat the pellet just past the port not way past.
You are going from a .140 port to a .177 barrel so the further from the port the slower the charge.
If you are curious about charge velocity look up choked flow.
K.O,
I appreciate you and WyoM taking the time and effort to explain the logic beyond a layman's perception of pumping vs desired result. That's what I came here for. Maybe one day I will be MIA as well once I had learned all the related knowledge - I hope not, I do enjoy looking at the pic of all the dressed up 13xx.
What I have in mind now is to find a bar stock, get a machinist friend to cut a groove in it to make it a barrel shroud and put it on top of the barrel between the steel breech and the pump/front sight linkage. The naked barrel with the space in between the tube is not eye appealing to me.