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PostPosted: Tue Mar 17, 2015 12:37 pm 
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Has anyone tried to partially fill the valve hole used to detune the Canadian Cr1377? A small sleeve might be epoxied into the hole. The factory hole seems to drop velocity down close to 400fps. A smaller bleed-off hole might bring it back closer to 500fps. Any thoughts on this?


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PostPosted: Tue Mar 17, 2015 2:15 pm 
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Plenty of thoughts on that. Discard that bleed hole valve, or plug it completely.
You can adjust for velocity between the hammer spring and number of pumps.
Pal Vagrant has a 13-77 that will do 470-ish (IIRC) on 3 pumps- this with a reduced volume non-bleed valve, balanced hammer spring, and flat top piston...

Regards,

Doc Sharptail

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PostPosted: Tue Mar 17, 2015 4:25 pm 
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Doc Sharptail wrote:
Discard that bleed hole valve, or plug it completely.
You can adjust for velocity between the hammer spring and number of pumps.

That idea was what Jmclean85 just got dumped all over for in another thread.
I guess you just can't win.

TCooper: maybe you could fill the hole completely and drill it out smaller?

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PostPosted: Tue Mar 17, 2015 9:45 pm 
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Doc Sharptail wrote:
Plenty of thoughts on that. Discard that bleed hole valve, or plug it completely.
You can adjust for velocity between the hammer spring and number of pumps.
Pal Vagrant has a 13-77 that will do 470-ish (IIRC) on 3 pumps- this with a reduced volume non-bleed valve, balanced hammer spring, and flat top piston...

Regards,

Doc Sharptail


Hi Doc,

Are you saying that the hammer spring can be adjusted so the 1377 will only produce 500fps with 3 pumps and also at 10 pumps? That would be great (keeping it non RPAL at 10 pumps).

Thanks


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PostPosted: Tue Mar 17, 2015 10:00 pm 
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TCooper wrote:
Doc Sharptail wrote:
Plenty of thoughts on that. Discard that bleed hole valve, or plug it completely.
You can adjust for velocity between the hammer spring and number of pumps.
Pal Vagrant has a 13-77 that will do 470-ish (IIRC) on 3 pumps- this with a reduced volume non-bleed valve, balanced hammer spring, and flat top piston...

Regards,

Doc Sharptail


Hi Doc,

Are you saying that the hammer spring can be adjusted so the 1377 will only produce 500fps with 3 pumps and also at 10 pumps? That would be great (keeping it non RPAL at 10 pumps).

Thanks


The way I understand it is, with the reduced volume, you'd get valve lock well before 10 pumps. I'm pretty sure Vagrant will show up with remarks of his own in the fairly near future...

Regards,

Doc Sharptail

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PostPosted: Tue Mar 17, 2015 10:27 pm 
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This is sounding good! A bit more velocity with less pumps... and a feature that keeps it legal (valve lock). I wonder how he reduces the valve volume. Likely some sort of sleeve in the valve.

Thanks


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PostPosted: Tue Mar 17, 2015 11:17 pm 
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I know he didn't arrive at his balanced set-up over-night. It took a bit of trial and re-trial, especially with the valve volume.

One way of volume reduction is using the "short" half of a 760 valve. That by it's self may not be enough, and yes, a sleeve that fits inside the valve is as good a means to the end that I have heard of.

I've experimented with industrial roller chain link-pin sleeves myself, with inconclusive results, mostly because I got distracted by new guns and new builds. This seems to happen a lot with me. :rolleyes: :rolleyes: :rolleyes:

You can also reduce flow at the transfer port to keep things legal. This was factory done at one time with a tiny washer under the port outlet, as well as the bleed hole.

I think some here may have missed the reduced volume aspect of the discussion...

Regards,

Doc Sharptail

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PostPosted: Wed Mar 18, 2015 1:28 am 
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tcooper wrote:
Any thoughts on this?

The factory bleed hole, ensures with a great deal of certainty, that the gun won't exceed the mandated speed limit, at even three times the factory recommended maximum # of pumps.
It is a low budget, lawyer approved, triple layer of CYA, at the expense of the common consumer expectation of manufacturer advertised 495ish performance....

As already mentioned, once the hole is soldered shut, it could easily be re-opened to any known drill size....

There's a host of ways to slow down a 13xx, many of which were manufacturer issued at one point or another, virtually all of which can be replicated at home: solder the transfer port shut, and
re-drill incrementally - fabricate a restrictor washer(tin can) under Transfer Port Seal - reduce the valve volume - reduce hammer travel - reduce hammer spring preload - increase valve
spring preload - reduce pump efficiency - increase headspace - reduce pump stroke length(pump tube intake vent).

There's plenty of both hammer weight and spring preload in a factory 13XX. My theory, is that Crosman hoped to emulate the Kalashnikov legend and be quite certain the gun
would still operate, immediately subsequent to unearthing from an extended adventure in a swamp/sandbox/lake/etc.....

Are you implying that you have a valve that exceeds 500 plugged? I've got/had 7ish 1377/2289's, and have never had a single one exceed 500 on 10 pumps with just a bleed plug. . . . :?

Still using an OE pump piston configuration? Is this the conversion to .22? What barrel length?

How many fps do you need to shed?
Doc Sharptail wrote:
... a 13-77 that will do 470-ish (IIRC) on 3 pumps- this with a reduced volume non-bleed valve, balanced hammer spring, and flat top piston...

The ultimate(read:pie in the sky)goal was 500 in 3, factory pump, drop in insert and proprietary valve spring. Marketable product, maybe. . . The particular gun under development is
ultimately intended as a birthday gift for my son; it does need to be "right" on the other end as well. .

Best durable tune so far, 3 pumps 420ish, 4 pumps 465ish, generously reduced volume, factory hammer and spring, no flat top, just factory pump assy...
There's more there, but it'll take lathe cut parts to achieve the tolerance required for durability. I had one real peach put together, which I optimistically thought was
gonna be the basis for the patent, but on the third or fourth evening I was playing with it over the course of a couple months, it ate virtually everything in the valve.
The hand cobbled replacement pieces obviously have looser tolerance, cause the peach's numbers are yet unchallenged. . . . Too many other things on the plate currently,
this gun hasn't made it back to the top of the list. . .
tcooper wrote:
Are you saying that the hammer spring can be adjusted so the 1377 will only produce 500fps with 3 pumps and also at 10 pumps? That would be great (keeping it non RPAL at 10 pumps).

Well maybe...
The easy way, would be to make a decompression device for the valve, flat top piston, 480ish in 3, and have the valve lock on the 4th. That makes what it does at 10 moot....

The hiccup is valve lock. In the above mentioned tune(under Doc's quote), it exceeds 500 at 10, and as they all do(plugged bleed valves) keeps going up from there. If there was
a degassing tool for this platform, then valve lock could be an in-the-field clearable inconvenience, but as delivered, clearing a valve lock requires partial disassembly.
Not a marketable product, nor one to gift to a child...

I really wanted to keep the primary mechanics as stock as possible. A previous rendition that did yield maximums of 497.6 on 10, only push ~365@3 and ~400@4, far
enough below criteria to consider as failure.

I'm confident that 470ish in 3 is durably attainable, I just haven't quite solved the 10 stroke part of the equation, which will
only get attended to, if/when the first
half of the equation is durably satisfied. . . .

Initially I'd envisioned a 3D printed insert, that could be sold for dollars yet made for pennies - hence trying to keep as many stock internals as possible.
I am however starting to lean in the direction of the above mentioned "easy way" for this gun. I do want my son to get it before his next, next birthday. . . .

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PostPosted: Wed Mar 18, 2015 10:09 am 
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Hi Vagrant,

Thanks for the excellent reply! Great details!

I don't have the pistol yet. I'm still trying to figure out whether to go with a 1377 or 1322. I'm hoping for 495 fps and prefer .177cal for economy. I'm understanding that 495fps could be done at 10 pumps with .177... but now I'm liking your idea of doing it in 3-4 pumps. Could you use Everhopeful's 2240 mod for degassing a valve locked 1377 pistol? Drill a 1/8" hole in the center of the tube plug (1322B002) and insert a rod through the hole so it rests on the hammer. Pull trigger and tap on rod to open locked valve.

You stated "I've got/had 7ish 1377/2289's, and have never had a single one exceed 500 on 10 pumps with just a bleed plug." I thought a plugged Cdn1377 will do around 530fps at 10 pumps (7.9gr). Not true? What is the correct velocity then?

You stated "The easy way, would be to make a decompression device for the valve, flat top piston, 480ish in 3, and have the valve lock on the 4th. That makes what it does at 10 moot."
What would a decompression device look like? Couldn't a weaker hammer spring work to open at 4 or 5 pumps but no more. Degas with rod if you accidentally pump too many.


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PostPosted: Wed Mar 18, 2015 1:16 pm 
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TCooper wrote:
You stated "I've got/had 7ish 1377/2289's, and have never had a single one exceed 500 on 10 pumps with just a bleed plug." I thought a plugged Cdn1377 will do around 530fps at 10 pumps (7.9gr). Not true? What is the correct velocity then?

Mid/low 490's on 10 with ~10" .177 barrel, 7.9 pellet.
Mid/low 480's on 10 with ~14" .22 barrel, 14.3 pellet.

I've never played much with an actual 1322, as I'm not a fan of the caliber. Everything I do is aimed at .177, not a hunter. . .

The primary issue with the bleed, is its effect on over stroking - A Canadian factory valve, will pretty much never valve lock, nor will it ever attain 500 in either caliber with the
respective 10" and 14" barrel, even when pumped 50 times. Plugging the bleed, pretty much ensures that at some number of pump strokes in excess of the factory
recommended max of 10, the speed limit is going to be exceeded, usually right at 11.

I will suggest that there could be a very few Canadian 13xx's that might very slightly exceed 500 with only a plugged bleed, but I'd suggest that they are the exception
rather than the rule. And here's why:

About 5 or 6 years ago, I purchased 4x "American" 13xx's at a local "Damaged Freight Clearance" wholesaler. I didn't really need 4 more of these at the time, but
after a short discussion with the manager, whereby I pointed out that these particular examples may not be technically "legal" for the Canadian market, it was decided
that if I were to take them all at a heavily discounted figure, his part of the problem would "disappear from his shelves". These guns were in boxes which claimed
600fps, and had un-vented(no bleed hole) all brass valves. Only two of them ended up apart on my bench, because of their respective shooting characteristics, the
other two were horse traded/gifted. When shot over the chrony, two were shooting dead on at 490ish at 10 pumps - all were over at 11, just like previous plugged
Canadian 1377s, but two of them were equally shooting 510ish. . . .

Curiosity required that one of each be torn down to find the source of the additional speed, and what I found was two different sizes of check valve inside the valve. The
larger check valved guns(reduced valve volume), shot hotter than the small check valve examples but neither style would hit the claimed 600, with even 25 pump
strokes applied. I've never seen the larger check valve in any Canadian market 13xx/2289, but I'm sure it could be possible, just like it could be possible to get one with
an un-vented valve. . . . .

TCooper wrote:
You stated "The easy way, would be to make a decompression device for the valve, flat top piston, 480ish in 3, and have the valve lock on the 4th. That makes what it does at 10 moot."
What would a decompression device look like? Couldn't a weaker hammer spring work to open at 4 or 5 pumps but no more. Degas with rod if you accidentally pump too many.

I'm positive that "the easy way" will work, the issue is/was dealing with the valve lock. Again, I am/was hoping for a marketable, more or less drop in device. Having to
drill a functional hole anywhere in a gun, isn't a problem for any of my personal pieces, but it sure cuts down on the sellability of the mod to most other shooters.

Heck, I still shoot/use the 1377 with the pressure gauge mounted in the side of the valve, but I don't advise that everyone should have a gun similarly equipped.
Quite frankly, while I'm personally comfortable that this gun is "safe", in the interests of personal/public liability, I don't really let anyone else "play" with
that gun. The anatomical grip ensures that it pretty much doesn't fit comfortably into anyone else's hand. :lol:

I truly believe that a "drop in" 470 in 3or4 <500 in 10 modification would be a profitable venture for the creator(hobby profitable, not retirement profitable :wink: ). If it
is completely reversible, it'd be a smashing success. If it's going to require drilling holes, cutting springs, any irreversible modification, appeal will be greatly effected, as
well as the effects of the desired outcome of the mod. Drill the hole slightly off, leave a burr behind, trim too much off the spring, not enough off, are all sources of
potential variable to the desired outcome. Then there's always the guy that'll completely fubar it somehow, and completely wreck his new toy. . . Not something
I'd wish to contribute to.

I'll have to search for Everhopefull's degassing mod, but I'm pretty sure I know what it is you/he's referring to, and I'm equally confident it'd be suitable
to the task. Another way would be a keyhole in the body tube and a degassing key similar to what is used on the QB-AR series of guns. Anyone lucky enough to
have one of "ustilgo's" Dual Power Hammers, has a degassing tool built right in already. . . .

I either need some custom cut valve guts, or I need to pick up some nest-able tubing/sleeve to move this project forward. Oh yea, and the time to devote to the
project. Four sons under the age of 12; it's truly a wonder that I get any "me" time at all... :mrgreen: This weekend is Beaver Buggy, Cub Kar, Scout Truck Racing,
which we've been fabricating/painting/decaling over the last couple weeks. The boys make them "look cool" and daddy makes sure they go fast! We've won, placed
or showed in every competition for the last 4 consecutive years. This year's the first time we'll have a vehicle in every category. . . Wish us Luck!

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PostPosted: Wed Mar 18, 2015 9:32 pm 
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TCooper wrote:
I thought a plugged Cdn1377 will do around 530fps at 10 pumps (7.9gr).

That was probably my bad - sorry. I thought they went over 500 if you just plugged the bleed hole, but I'm not actually sure I ever measured it. Both of mine have 24" barrels, flat top pistons and non-standard transfer ports, so I've had to struggle to keep them under the limit. I like detuning via the hammer spring because the light spring makes the cocking cycle so nice. The down side is that you quickly get retained air, so unless you dump that between shots (which seems wasteful) you get a lot of shot to shot variation in fps. Dramatically reducing the valve volume sounds like a neat idea - I should play with that sometime. My latest went the other way - I added extra volume for multiple shots :)

Jim


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PostPosted: Thu Mar 19, 2015 9:35 am 
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vAgRaNt wrote:






Four sons under the age of 12; it's truly a wonder that I get any "me" time at all... :mrgreen: This weekend is Beaver Buggy, Cub Kar, Scout Truck Racing,
which we've been fabricating/painting/decaling over the last couple weeks. The boys make them "look cool" and daddy makes sure they go fast! We've won, placed
or showed in every competition for the last 4 consecutive years. This year's the first time we'll have a vehicle in every category. . . Wish us Luck!


Good luck then! :mrgreen:

Regards,

Doc Sharptail

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PostPosted: Sat Mar 21, 2015 7:57 am 
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You may want to read the post Bob made on keeping the 1377 non RPAL .
topic27385.html?hilit=the%202289%20crosman%20should%20have%20made


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