ASG CZ BREN 805 A1 feeding issue

[n0tr3adY]

Hello guys!
I'm searching through the internet since a week, and can't find any solution for this.

Here it goes:

Shooting on semi the bb's fall out after 3-4 meters, chrono test shows 250-320 fps. Changing fire mode to auto after 2-3 bb's the air leak disappears, and the feeding goes well and the fps goes up to 380 +/- 10 fps (with m110 spring).. Easy to reproduce the malfunction, change mags.

The gearbox shimming and air seal is perfect.

I have some experience on ver2 / ver3 gearboxes, but never experienced that kind of malfunction.

Thanks in advance!

 

Upgrade parts:

- ASG 40k Ultimate motor

- Specna Arms 16:1 gear set

- Slong 100% (full) cylinder

- Slong 14 teeth piston

- ASG POM vented pistonhead

- SHS cylinder head
- Airsoftpro nozzle (same lenght as original, 34.1mm)

- King Arms delayer (stock)
- Maple leaf 70 rubber + omega nub with Maple leaf 6.02 tightbore barrel

 

[Adolf Hamster]

try swapping the maple leaf out for something else, i tend to find the feed lips are too long and give similar symptoms.

you can sand them down a bit, but it's kind of a pain in the ass.

 

[Asomodai]

Are you using fully loaded midcaps for the first few shots? If so, half fill them then try semi. 

Could be midcap syndrome. 

 

[n0tr3adY]

Are you using fully loaded midcaps for the first few shots? If so, half fill them then try semi. 

Could be midcap syndrome. 

Click to shrink...

Already tried with the bren stock high cap magazine (have both magwell), same. 

 

[Prisce]

Sounds like it could be the nozzle not sealing correctly. Try the SHS nozzle with the cylinder head, I don’t know what compatibility is like with the Airsoft Pro version.

(Had the same issue with a M60- hence suggestion) 

Do your bbs fly every direction, or just out and drop?

 

[n0tr3adY]

Sounds like it could be the nozzle not sealing correctly. Try the SHS nozzle with the cylinder head, I don’t know what compatibility is like with the Airsoft Pro version.

(Had the same issue with a M60- hence suggestion) 

Do your bbs fly every direction, or just out and drop?

Click to shrink...

The nozzle seals perfectly in opened and closed state. The bbs flying for 2-4 meters in same direction then drop. There is only one type of aftermarket nozzle for Bren, because it's very long (34.1mm) - i had to replace the stock one because it leaks.

 

[Prisce]

The nozzle seals perfectly in opened and closed state. The bbs flying for 2-4 meters in same direction then drop. There is only one type of aftermarket nozzle for Bren, because it's very long (34.1mm) - i had to replace the stock one because it leaks.

Click to shrink...

Then it’s definitely hop related. Either the hop unit is putting too much pressure on the bucking, the bucking isn’t in 100% square, the nub has moved or like @Adolf Hamster said, the bucking may be to hard.

 

[n0tr3adY]

Then it’s definitely hop related. Either the hop unit is putting too much pressure on the bucking, the bucking isn’t in 100% square, the nub has moved or like @Adolf Hamster said, the bucking may be to hard.

Click to shrink...

Maybe..The BREN has unique hopup chamber (yt video), the nub can't move just up/down. 70° Maple leaf with Omega Tensioner (dedicated use with maple leaf rubbers).. I thought it was soft a bit for 0.3 - 0.32 bbs. I have a green G&G 60°, i'll throw a try.

Edit : replaced the rubber to G&G 60° with a softer nub, still feeding problems.. I'm starting to think my caps are sh1t.

 

[KOBK81]

I've been experiencing problems with my Bren the last couple of days. I've recently swapped out the hop rubber and nub due to wear. I replaced it with a madbull blue rubber and nub. After reassembly I've been getting very random bb trajectory and misfeeds. I turned the hop all the way down and it's even worse the bbs are now going up almost like it's over hopped. I've discovered after several hours of taking apart and reassembling that the rubber and nub are to hard for the gun. I believe that the original rubber is a 50deg which was working fine and givin consistent accuracy and the mad bull one is 70deg. I've also discovered that the Bren doesn't like specna m4 mid caps. I'm going to flat hop it and try the prometheus soft black rubber with a prometheus flat nub and see what I come up with.  

 

[Adolf Hamster]

Madbull blue rubbers are godawful, get that out of there.

If you want a standard rubber then g&g green or prommy purple.

Something a bit fancier then pdi's w hop (still takes a standard nub)

If you need to lift the heavies (.36 and up) then maple leaf macaron.

Flathops are a good cheap upgrade, but can have a very narrow "sweet spot".

 

[KOBK81]

Madbull blue rubbers are godawful, get that out of there.

If you want a standard rubber then g&g green or prommy purple.

Something a bit fancier then pdi's w hop (still takes a standard nub)

If you need to lift the heavies (.36 and up) then maple leaf macaron.

Flathops are a good cheap upgrade, but can have a very narrow "sweet spot".

Click to shrink...

The mad bull blue is in the bin. I fitted one to a g&p m4 and was hopping 0.28 lovely but the Bren really didn't like it. The lip was all wrong and the nub was way to hard. For now I've stuck a random black rubber in there and a flat nub along with a 6.03 barrel and tbh it is actually working quite well. I've spent most of the morning testing it with 0.25 and been sending bbs out to around 70 yards which is further than what the stock rubber and nub were doing.I've picked up a m125 element spring which I'm also going to give a go. I have ordered a promy black and a namazu firefly which will be here next week sometime. So hopefully I will be seeing the 100yd mark. 

 

[IainShep]

The Bren wiring is tricky. It wraps around the front of the gearbox, if it isn't tucked neatly the hop gets pushed to the side. Mine had feeding issues as well as low FPS. My problem was due to me using silicon wire, ended up switching over to the silver coated teflon stuff as it's not as wide.