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Discussion Starter · #1 ·
Hello!
I bought a used CA m24 some time ago.
The previous owner said that there is a problem with the hop-up, so I rose to the challange and bought the gun anyway, since I had some spare parts available.
First thing I noticed was that the hop-up bucking was torn up pretty bad, so I replaced it with a similar right away (PDI). Also some of the screws on the PDI hop up chamber were in a pretty bad shape so I replaced them aswell. Everything else was in pretty good condition so I put i all back together, and tried to shoot. The first time I cocked the gun and fired, nothing happened. I cocked again, and the bb shot. I repeated this for a while, and it turns out that upon shooting the bb either just falls out of the barrel once you push the cylinder forward, or it shoots, but in some cases pretty bad. The gun never shoots on the first cocking. I tried a guarder bucking, but that didn't do the trick. The hop-up is obviously set to the lowest setting, so the bb doesn't get stuck on it.

Has anyone got any ideas about what could be the problem, and possibly on how to fix it? :shrug:
 

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Discussion Starter · #7 ·
Checked the internals earlier today. Nothing seemed to be broken or anything, though the cylinder head was pain to put back on, since the piston was very tight. And by tight I mean you needed 2 guys to put it back together. The whole cylinder set should be PDI. I don't know anyone who has had this problem, nor did I stumble upon anything on the internet..
 

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He may have done something with the cylinder head nozzle so it doesn't seal with the bucking. Compression test the whole gun.

Take the end cap off the gun and WITHOUT the gun being loaded put your finger over the end of the barrel fire the gun.

Assuming you have all PDI internals you should have damn near perfect air seal. Just listen to hear if the piston hits the cylinder head. If it does with little resistance from your finger being over the end of the barrel you have a leak.

Alternatively you can test the compression of each part by doing similar tests.
Put the cylinder head into the hop up chamber and push it forward. Stop the end of the barrel with your finger and blow through the cylinder head.

My guess is that he has the wrong cylinder head/cylinder on it and it isn't physically pushing the bb into the bucking so it can be fired. Thats why on the second shot it rolls out the end of the barrel. The first bb moves into the bucking and the bb behind it stops the air.

Measure the cylinder head. I'll get a measurement of my stock cylinder head to see if they are comparable lengths.
 

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Can you physically put a bb into the chamber, and see the cylinder head push the bb into the chamber?

If not, take a look over at Vindi's guide in the AEG section, and he shows how to lengthen you cylinder head. It is a fairly easy mod, and cheap to boot.
 

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Discussion Starter · #10 ·
I didn't quite manage to get the end cap off, but by doing other measurements I can state that there are no leaks.
I'll get the cylinder head length by tomorrow, I need to go and grab some better tools. I think the problem indeed might be that the cylinder head isn't long enough, but again, I'll return to you guys with more information tomorrow.
By the way woogie, exactly which part on the guide is about lenghtening the cylinder head? I'm reading about a whole different topic here.
 

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Discussion Starter · #11 ·
All righty, I measured the cylinder head, and here are the results:

Cylinder head (without the thread part, so it's the part of the head that comes out of the cylinder) - 22mm
The actual nozzle on the cylinder head - 19,5mm
 

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Overall length:
29.49mm
Length of nozzle:
19.54mm
OD of of nozzle:
5.98mm
ID of nozzle:
4.10mm

I'll post the pictures in a minute but it really isn't necessary as long as you understand what i said just above.
To me it doesn't look like the nozzle is the problem.
.
.
.
 

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Discussion Starter · #13 ·
Indeed.
The mesurements seem to match. I was kinda hoping the nozzle was the problem so atleast we know what the problem is.
Now I'm just weirded out... What could possibly cause this? :shrug:
 

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Discussion Starter · #15 · (Edited)
I tried to shoot a video, but it didn't turn out the way I wanted so I really don't think it would clear things up any further.
Goldentrigun's recap of the bb's behavior suits perfectly, but since the nozzle length seems to match up, that can't be the case. I was sure the problem was in the nozzle.

Edit: Just checked the small screw that tightens the hopup chamber to the outer barrel, and the threads are all messed up. Could it be that the hopup chamber moves to a point where it's too far away for the nozzle to push it? Only the very bottom threads are intact which explains the screw hasn't fallen off yet.
 

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I tried to shoot a video, but it didn't turn out the way I wanted so I really don't think it would clear things up any further.
Goldentrigun's recap of the bb's behavior suits perfectly, but since the nozzle length seems to match up, that can't be the case. I was sure the problem was in the nozzle.

Edit: Just checked the small screw that tightens the hopup chamber to the outer barrel, and the threads are all messed up. Could it be that the hopup chamber moves to a point where it's too far away for the nozzle to push it? Only the very bottom threads are intact which explains the screw hasn't fallen off yet.
I've never used that screw and not had a problem. Without that screw,when you shoot, the impact of the piston against the cylinder head will push the hop up and barrel ever so slightly forward to the point where it can no longer advance, due to the design of the outer barrel. Basically, the purpose of that screw is to prevent that from happen, not because it should cause problems, but because it makes it a PITA to get the hop up unit back out.

If you didn't have to physically pry the unit out, I suspect that that isn't the problem.
 

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Is it possibly an APS 2 unit? They'll fit, but loosely in the outer barrel. Or, the V1 M24 units, if I remember correctly had some issues. It's been awhile, so I don't remember what it was, but it's worth checking in to.

I know the initial version 1s were goldish, but the newer ones went to the standard black before being replaced by the black version 2s. The color difference is the only way I know to tell them apart, as I have no experience with the version 1s at all.
 

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I have been helping steve with this gun and it is a black unit. but its not the same PDI aps unit as I had, because this one has a little flat space on it where you tighten up the screw through the outer barrel, so I guess it is the m24 one...... not sure though.

And as steve mentioned, we are probably going to test my FF aps cylinder set just to make sure that that isn't the problem.
 

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Discussion Starter · #20 ·
Tried the FF aps cylinder set and miraculously it worked. The PDI pistons are something I consider rubbish so I will probably bin em. Ordering a new piston worked out fine.
Thanks guys for helping me out!
 
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