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ZipSnipe · Veteran Member

Ok I have 3 crosman 1077's.

One has been tuned by Big Daddy Joe and it works like a dream.

The second one is the brand new one that I used in my bullpup mod and has a leak, leaked out quik could only fire a couple of shots.

The third one is the flea market find that I replaced every seal in it and it too leaks, I was able to fire a clip and half off.

My question is, the piercing part of the tube, it has two notches to tighten it down, should it be real tight or snug ?

AirGunEric · Site Admin

I assume you mean the screw-in hold down for the Co2 seal?

Snug, then tighten a bit more, but not "cranked" with a heavy screwdriver as this will deform the seal excessively.

Is the leak coming from that seal, or the Co2 tube seals? Also, if you lubed the seals when replacing them, they may leak a bit until the oil is blown off (I have found out over many many repairs of different Co2 guns that oil on seals when putting new ones in tends to cause leaks- which usually go away after a bit- although if the leak is extreme, maybe not. Use oil on a re-seal job sparingly).

ZipSnipe · Veteran Member

No I mean the part that actually punctures the co2 capsules.

AirGunEric · Site Admin

The piercing pin (#38A027) does not screw-down- it is retained by the 38-128 seal, both of which are held in place by the threaded collar #338-041.

There is no way to screw-down the piercing pin by itself.

ZipSnipe · Veteran Member

Then I guess I am talking about the threaded collar, I assume this should be nice and tight?

And here is another weird thing, today I grabbed the 1077 bullpup and it fired perfectly with the same c02 cartridge that I put in it yesterday. But when I went to shoot yesterday, the first few pellets fired fine but then it acted as if the c02 had leaked out and was firing very weak puffs of air into the ground. Now it shoots like a high powered rifle, hell it scared me because it was louder and you could feel the power when you pulled the trigger.

Fired it at a 1/4 piece of plywood with a piece of Hardi board behind it and it went through the plywood ,hit the hardi board and ricochet right back at me twice.

Any ideas on that one? I haven't tried the Flea Market 1077 yet to see if it had the same result, I was still shaken up by the bullpup almost taking me out.

AirGunEric · Site Admin

Re-read my first post here. Stop, consider what is being stated, then respond if/as required.

ZipSnipe · Veteran Member

Thanx Eric , I appreciate your help, both guns seem to be working fine now.

ZipSnipe · Veteran Member

Well I guess I am going to take that back , only the one gun is working and the brand new gun is leaking c02 quickly. However this is the new 1077 that I used in my bullpup mod. I did have to take the c02 piercer part out so I could extend the tube. So this might be my fault and I will have it apart tonite.

I thought the problem was fixed but then it reared its ugly head, I also discovered that I didn't correctly lock the ammo clips which will definitely cause misfires.

So I will have it apart but I am also out of c02 so have wait for mullah to show up in my pocket

ZipSnipe · Veteran Member

So Eric, I took your advice put the trigger back together without the lil flap and you are correct it works fine.

However when I put a c02 tube in it I can hear a leak, at the back of the valve it was all oily . Now when the hammer hits the back of the valve is there supposed to be a small release of c02 out the back of the valve?

ZipSnipe · Veteran Member

Ok got the valve apart. The piercer pin was rusted. This the new 1077 I bought. So I cleaned up the piercer and I also lightly sharpened it.

Also the lil rubber part that seals the hammer pin was very loose. So Crosman is sending me a new one. However I discovered the little brass washer that the rubber seal goes thru is also seems like its a little small for the valve opening allowing c02 to escape. They are not sending me that part but we'll see how it goes once I get the new seal.

I like the old valve way better than the new. The old one had the screw on cap while this new one has a retaining clip. Maybe I will see if they have any old valves and just order one of those.

ZipSnipe · Veteran Member

Well got the new seal for the hammer pin. However it is waaay looser than the old one. So I measured everything with some calipers. The hammer pin diameter is .107, the old seal hole diameter was .111, the new seal which is made out of delrin is .123.

Now when I look at this valve assembly , it seems to me that when the hammer hits that pin, that you would want a pretty tight seal to keep the c02 from leaking. So I assume that the hole for the seal should be around .109 at the largest.

Now the great customer service at Crosman are sending me another new seal and a hammer pin. So maybe the hammer pin on mine was just too small.

Being that I used to work in the tool and die trade, I know how easy it is to a take a few thousands too much off, so an easy honest mistake.

However I am ready to get this thing finally working. And why it would seem to work sometimes and not others , who knows. Will update when parts arrive.

ZipSnipe · Veteran Member

Well while I have been waiting for the new pin to arrive. I was pondering why they have the seal loose over the pin, then it dawned on me that the c02 freezes everything it touches so there would be shrinkage.

This caused me to research the delrin properties and discovered that the delrin is not a good seal as it turns brittle when frozen.

So they are sending another seal too with the pin, I guess we will have to see what they send me, hopefully a black rubber seal like the old one.

ZipSnipe · Veteran Member

Finally success!!!!! New transfer tube and seals did the trick. I believe it was the transfer tube that was causing the leak as it was .002 smaller in diameter than the new one.

Such a sad story though to have to completely rebuild the gun for the manufacturer. But they were very helpful and sent all replacement parts at no cost to me. This weekend I will post pics and fire several clips before I past final judgement on if the gun is finished. Thanx to all who have been keeping track and hopefully some will learn from my experience.