My 1377 project

[Mintyman]

  Since I’ve got my 2 new 362’s and the old 766 dialed in and shooting great I’ve really enjoyed shooting pumpers again. I asked my son if he still had the old pellet pistol and he brought it over. I forgot it was an early 1377.
 It wouldn’t hold air. I added a few drops of pellgun oil and got it to kinda pump up but it was very weak. I had ordered a plumper pumper forearm that fits perfect and makes it easier to pump.  It’s performance stunk. Pellets flying everywhere. It all leaked so bad.
I was not happy so I tore it all apart. I replaced the orings in the valve. I tried to install one of the plastic breeches from one of my 362’s but it leaked air badly at the barrel to breech/ bolt seal. I put the original sliding brass bolt back in for now with a new bolt ring and got it sealing nice. The barrel was filthy and (after I pulled a few patches thru) has no rifling left from shooting bbs.
I’ve got a bunch of parts coming  from MellonAir and a few others to turn this scattergun into a shooter.

[moose]

I'm very interested on how you get this older 1377 revived !!

[Mintyman]

Is this a big issue?
  When they stamped the serial number into the pump tube they dimpled the tube. I have to drive out the valve with a dowel and a hammer. I thought it was a burr but nope. I have no idea how to remove the dimple. I can feel it with a dowel. It doesn’t damage the oring and I don’t think I have any leakage with the stock setup.
 I have a flat top valve and piston on order. I hope it won’t matter. 

[Tack Driver 10]

I think you have a combination of two issues.
The heavy stamping on the pump tube.
The valves halves are misaligned.
I've seen over .010" mismatch on some of the older brass valves.

I have several of these old 13xx guns and they can be made to shoot.

[Mintyman]

The valves halves are misaligned.
I've seen over .010" mismatch on some of the older brass valves.

I have several of these old 13xx guns and they can be made to shoot.

What do you mean by misaligned? The rear portion of the valve body is machined different then the front. When I took the gun apart the exhaust port wasn’t centered in the transfer port. After I put the new orings in and reassembled the valve the port and trigger group screw hole line up perfectly.

[Tack Driver 10]

Here's a picture of one.
Since the heavy scrape is only on the front valve half I believe this is your problem.

[Mintyman]

Hmm I’ll have to check that when I get home. I never thought about that misalignment. It just appeared that the rear portion was turned slightly undersize compared to the very snug fitting front. I’ll check it when I get home.
I do have a flat topped piston and valve on order from MellonAir. I’m hoping the dimple won’t interfere with the new piston.
Thanks.

[Tack Driver 10]

The new aluminum valves are CNC machined so you should be good.

[Mintyman]

I’ve got parts on the way to so I started cleaning up parts. I filed and sanded the casting marks from the trigger frame. I’m not sure if I’m going to polish it all or repaint. I made new trigger and sear pins from a#30 drill bit shank. That tightened up a lot of slop in the trigger pivots. I’ll find some washers tmw and polish to fit. I messed with a few springs and a.22 case. I added a piece of dowel as a trigger stop. I’ll see how it works. It seems to test fine. (I like how easy it is to adjust the trigger on these). I have a few extra springs to try when things start to gel. Im really worried about the serial # dimple in the pump tube. The pump tube dimple is right in the piston stroke area. The stock cup seal has a flat spot matching the gouge on the air valve. I sourced a new pump tube so I’m waiting for that. 
This is turning into an expensive gun. Lol.   

[moose]

I just got a NEW 1377. I noticed the transfer port is slightly off center ... just leave it alone ?

[Mintyman]

The transfer port was off center on this one when I first too it apart too. The 2 halves of the air valve werent aligned in my case due to a bad o ring. It should be dead center in the air tube.

[moose]

I will take the air valve out and give that a look. I have it torn apart for another mod anyway

[Mintyman]

I’ve learned a lot about the 13xx guns these past few weeks. 😁
A lot of fun but there’s a lot of pumping. 

[gloob]

I don't think any of mine are perfectly centered. You can try loosening the grip subframe and twisting the pump tube a little to get the hole closer to centered. But it's no big deal. The barrel just ends up slightly to one side or the other of center.