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PostPosted: Thu Sep 09, 2021 5:21 pm 
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Joined: Tue Nov 18, 2014 12:23 pm
Posts: 218
Location: Calgary
I've recently picked up a new 1377 (on sale at Princessauto) and today I picked up a nice older used one. To my surprise they are no faster than my 1322, in fact they are a bit slower (new one is faster than the old) than my 1322. The other thing I noticed is that it doesn't matter how many times I pump them past 10 pumps, they don't seem to speed up much where as the 1322 will keep gaining speed but at a rapidly diminishing rate compared to the number of pumps.

Does the 1377 have a different valve or something than the 1322? My unmodified 1322 does around 440fps at ten pumps with a 14.3gr pellet and it does 499+fps with 20. The older 1377 does around 400fps with 10 and about 430 with 20. The new 1377 does about 440 with 10 and 450ish with 20 (7.9gr pellets).

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PostPosted: Thu Sep 09, 2021 5:29 pm 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1998
Location: Spruce Grove AB
They use different sizes of ports and bleeder ports. They used to use spacers inside the valve to take up more or less volume.
Basically your valve can take over 2000 psi, iirc, but your plastic piston basically fails at pressures closer to 1000psi, so you can't pump it up past the maximum pressure, no matter how much you pump.

You can get better pressure by using a different flat top piston and machining the face of the valve flat. At that point it's easy to get 500fps with less pumps. But you need to tune it so it won't go over that limit.


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PostPosted: Thu Sep 09, 2021 11:41 pm 
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Joined: Tue Nov 18, 2014 12:23 pm
Posts: 218
Location: Calgary
My curiosity got the better of me and I stiped the older 1377 apart and I also took the breech off of the new 1377. As noted above the transfer port is smaller, much smaller in fact. Also, as noted, there is a small (about the same diameter as the hex key that fits the small breech screw) bleed hole in the hammer side of the valve that lets air by pass the transfer port. I did not find any spacers or anything else inside of the valve but the aluminum valve bodies are crap compared to the brass ones. There was some corrosion in the older 1377 valve which was aluminum.

I fitted a larger 2240 transfer port to the new 1377 and it jumped up to the 470-480fps range with 10 pumps and 499+fps with fifteen pumps. This puts in closer to the claimed 495fps with ten pumps. There is no way it was going to get near the claimed range with the small transfer port. I think blocking the bleed/bypass hole would likely put it just about right on 495fps.

_________________
Slavia 630/77
Slavia 624
1322
1377
2240
2240/2260 20"
WF600
Vantage .22
Vantage .22 (.177 if the barrel shows up)
Walther Falcon Hunter .22
Walther Talon Magnum .25


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PostPosted: Fri Sep 10, 2021 12:05 am 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1998
Location: Spruce Grove AB
The bleed hole just guarantees crosman that nobody can pump the gun into oblivion to get 1000fps out of it.

There are tons of mod and build threads here on the forum pertaining to the 1377. You should definitely check it out.

But you got the bug now, you're fiddling and putting better parts into it and that's exactly how it starts :lol:

I once tuned one up nicely, a 1322, to shoot just under 500 fps with 5 pumps. Couldn't shoot any faster, you'd just retain air in the valve until the valve locks up.

So, there is a whole lot about the 1377 valve! :wink:


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PostPosted: Fri Sep 10, 2021 12:50 am 
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Joined: Tue Nov 18, 2014 12:23 pm
Posts: 218
Location: Calgary
How did you get enough air in five pumps? I've been considering the flat top piston and valve but more money and I'm not sure about the durability of the O ring vs the stock pump cup. A solid metal piston with a crosman cup seems like a good way to go but will not reduce the required pumping I don't think. I'll have to research it some more. I'm working on a 1377, 1322, and 2240 project at the same time and mix them up in my head a little I suspect. I just got an adjustable hammer spring unit for the 2240 only to find that I already had a new one in my parts collection from years ago. I also just tried putting a steel breech on one of the 1377s only to learn that the bolts are different... moving to fast.

_________________
Slavia 630/77
Slavia 624
1322
1377
2240
2240/2260 20"
WF600
Vantage .22
Vantage .22 (.177 if the barrel shows up)
Walther Falcon Hunter .22
Walther Talon Magnum .25


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PostPosted: Fri Sep 10, 2021 1:29 am 
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Joined: Thu Oct 13, 2005 4:20 pm
Posts: 1998
Location: Spruce Grove AB
I reduced the valve internal volume by quite a bit, then clipped the hammer spring til it was just right. Used a flat top piston with the oring. If you get the right oring, a 90 duro urethane is the best but a buna will do just fine. They last pretty good, you just gotta oil them lots.

The modded cup piston is one way, but I figure harder to make. and the removal of the tapered valve face also removes some headspace between the piston seal and check valve. Little more pump efficiency.

Parts get mixed up, it happens :lol

For your steel breech 1377, just punch the handle out of the original bolt probe and tap it to fit the steel handle that came with the breech. Should do the trick. I done many like that.


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PostPosted: Fri Sep 10, 2021 5:48 pm 
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Joined: Tue Nov 18, 2014 12:23 pm
Posts: 218
Location: Calgary
Today I put a 1377 stock barrel and bolt on a 1322. Surprise, 495fps with 10 pumps. I probably shouldn't say what it did with 20 pumps but I guess it is why they neuter the valve and port in the 1377.

_________________
Slavia 630/77
Slavia 624
1322
1377
2240
2240/2260 20"
WF600
Vantage .22
Vantage .22 (.177 if the barrel shows up)
Walther Falcon Hunter .22
Walther Talon Magnum .25


Top
 Profile  
 
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