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Thread: German-market (F-Type) Crosman 1377

  1. #1
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    German-market (F-Type) Crosman 1377

    Hello

    I ordered my 1377 from Germany as I couldn't find it for sale through a professional reseller here in France. Turns out Germany limits airguns at 7.5 joules ("F-Type"). From what I've seen this is not that far from the power a stock 1377C makes, but since France allows 10 joules maximum I'd like to try and get the pistol as close to that value as possible. I'm planning to order the flat top piston kit from GMac Custom Parts, but are there other things I sh/could do? Any ideas how the pistol may have been bridled to 7.5 Joules?

    For the rest I don't regret my choice. The pistol seems pretty accurate: I sighted it in from about 5m, in a standing position resting my hands on a support, and got several pellets through the same hole on more than 1 occasion. It doesn't feel as much alive as the Webley Premier I had before, but certainly more than the HW40 I shot a couple of times!
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

  2. #2
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    Aug 2004
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    10 joules is roughly 7ftlbs.
    Flat top piston and valve is a good start and will increase power.
    An aftermarket breech and extended bolt is a must for me. The crosman steel breech and gmac's hollow extended probe is a good combination. Replace the metal transfer port with some poly tube the same diameter prevents lost air. A smoother hammer spring makes shooting nicer as well.

    I've been tinkering with my crosman pumper carbine the past couple of days and am getting 10.5ftlbs with 13pumps. But mine has a longer barrel and i've modded the valve insides. I reckon with the stock barrel and all the above mods you could get around the 10 joules mark with 8-10pumps.
    Danny
    My collection = Ratworks BSA Scorpion T-10 .177, HW100KS .177 (tweaked by me), PP750, Crosman 1322 and 1377

  3. #3
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    Hello Danny,

    Thanks for the suggestions. I've already installed the GMac extended brass breech (I wanted to keep the stock sight without modding it...) with the extended probe. I understand they don't do a hollow probe for the .177 version - what's the point anyway? I've also added a transfer port top seal, I'm guessing that has more or less the same effect as replacing the metal port with a vinyl one. Also deburred the transfer port.
    I have the impression that this already increased the power - I'm now shooting through board that resisted previously.
    The flat top piston kit from gmac will be next.

    In fact, I was a bit concerned that there might be some security valve somewhere that would continue to limit the max output - any ideas if that's likely or rather not?
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

  4. #4
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    There will be a bleed hole on the end of the valve near where the valve stem exits if there is one at all. I know the Canadian versions have this, I had a 2289 backpacker from Canada which had one. It prevents the valve reaching high pressures. If youre getting a flat top piston and valve from gmac then I wouldn't worry about this.

    Gmac does have the the hollow probes in 177 now. They definitely increase fps, exactly how I don't know, probably channel the air more efficiently behind the pellet. He has videos showing this. They also make loading easier and smoother I find.
    Danny
    My collection = Ratworks BSA Scorpion T-10 .177, HW100KS .177 (tweaked by me), PP750, Crosman 1322 and 1377

  5. #5
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    Yes, I also understood the Canadian versions have some kind of bleed valve (from the review on replicaairguns.com). And I was indeed hoping that by installing the flat top kit, I'd simply be getting rid of anything of the kind

    I'm a bit peeved I didn't notice the hollow probe for .177 ... I can easily imagine how it makes loading easier (maybe even compensating for the increased difficulty with the gmac breeches?). From the image it would seem that it sits over the transfer port and thus maybe helps to concentrate a bigger amount of air directly into the pellet skirt? I haven't seen a lefthand version though, have you?
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

  6. #6
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    If you get the left handed breech, I think the bolt is threaded through so you can screw the handle into the other side - is that what you mean?
    Danny
    My collection = Ratworks BSA Scorpion T-10 .177, HW100KS .177 (tweaked by me), PP750, Crosman 1322 and 1377

  7. #7
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    I think I'll have to ask confirmation. The bolt that came with the left-handed breech is not an ambidextrous design; the handle screws in on one side only.
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

  8. #8
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    FT piston/valve install

    Coming back to this subject: I received the GMac FT valve & piston kit, and am looking for some advice on how best to install it - i.t. with minimal disassembly (surprisingly I haven't yet found any 'tutorial' online). Looks like the air chamber/valve is held in place with a single bolt or screw; is that the front screw that holds the trigger assembly to the main tube? Even if it is, I'm guessing I'll have to drop the assembly in order to unload the pressure exerted by the hammer spring? Does that mean the breech has to be taken off too (to avoid damage to the transfer port seals maybe?)
    If one has to disassemble to that point, I guess it'd be best to do the extraction and insertion of the new chamber via the rear end of the tube?
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

  9. #9
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    The whole gun has to come apart in order to get the valve out. Its quite simple to do really.
    1. First remove rear breech screw and the small breech screw under the bolt in order to remove the whole breech and barrel from the barrel band. Also remove the transfer port and seal.
    2. Remove trigger frame screws - front and back. The front one screws into the valve. Watch out for the tiny safety spring screw and ball bearing. Keep the pistol upright when you do this.
    3. Next extend the pump arm and tap the pivot pin out using a punch and hammer. The barrel band can then be removed then with the piston.
    4. Tap the piston pin out and replace with the flat top. You will need to adjust the piston when reassembling.
    5. From the back of the pump tube - use a piece of dowel, I use a wooden chop stick to gently tap the valve out. The valve has to come out the front of the pump tube, so tap from the back.
    With regards to adjusting the piston - you should feel the piston end meet the top of the valve when the pump arm is about 1/2inch from closed.
    A heavier hammer spring will allow the valve to dump more air. Inside the valve, the valve return spring determines the amount of air taken in during each pump. The lighter the spring, the more air is taken. Also a lighter return spring means the hammer spring can dump more pumps.
    I'd recommend a slighter lighter spring for your valve and a sdcustomdesign hammer spring and guide for smoother firing cycle.
    Danny
    My collection = Ratworks BSA Scorpion T-10 .177, HW100KS .177 (tweaked by me), PP750, Crosman 1322 and 1377

  10. #10
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    Thanks Danny! I'd already found "miketheknife's" disassembly video on youtube, but more instructions is better than less
    Does the valve have to go back in the way it came out? (I suppose it could well become obvious once working on the gun ... but it'll be a few more days before I can get my hands on it again.)

    René
    mad(dened) scientist, fulltime nerd, (early) music/photography/Moto Guzzi geek, discovering the joys of shooting

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