Lock Up On Semi-Auto Help

[jagillham]

Hi everyone,

I'm new to the forum, and have just started occasionally airsofting again. Its been a long while since I played regularly, back in around 2010 I was quite obsessed playing most weekends for a good few years, and was a regular on the ZeroIn forums which now seem to be gone!

I know my way around an AEG, and my current set up is pretty custom based on a G&P VLTOR. It was a very good set-up back in the day, but it seems things have caught up a bit since then.

I've got a new issue, which about coincides with installing a new spring/piston. I'm getting lock up on Semi, which can be solved by flicking to auto. Sometimes it needs a few shots too. I think it was a Guarder M100, but I'm trying find the order receipt. I'm getting around 285fps on .25s (so about 320fps on .20s), air seal is good, but I lose a little fps due to the sorbo pad / air brake piston head.

Other relevant parts are...

- ASCU MOSFET (very early model, probably their original one! Takes up half the stock tube. Microswitch for the trigger)

- 7.4 2200mah 35C Giant Power LiPo

- SHS High Torque Motor

- SHS 13:1 gear set

- Anti reversal latch removed

I'm not convinced the spring is the issue given it is not particularly strong, and it gives about the same FPS as the one I took out (which was an unknown make/strength).

Any help on what to try next is appreciated. I'm not really playing enough to justify spending loads going around changing every part hoping something works!

 

[Adolf Hamster]

Got active brake turned on?

Because this sounds exactly like an active brake stopping the cycle too quickly problem

 

[Skara]

Oh god...

Air brake piston head, ASCU, ARL removed

That thing is straight outta the early '00s!

If I'm not mistaken that thing still uses a cutoff lever to recognise the gearbox cycle... Which as elaborate as it can be it will never get rid of the occasional semi lockup.

If you don't mind renovating the gun a little, I would suggest to get rid of the ASCU and install an optical FCU of some sort, I'm a big fan of the Perun Hybrid but Gate Titans/Asters work very well too. They eliminate the COL so the cycle detection is made by optical sensors, which also completely eliminates the chances of locking up in semi (gearbox always stops in the same position, every time)..

 

[Rogerborg]

Ahoy and welcome and what they said and also

View attachment 60896

 

[jagillham]

It is a bit of a classic design I know... but then again I used to play back when a 9.6v nimh in a battery sling was a good set up! ?

The set up has worked for years without a semi lock up issue, and for the few times I played in 2023/2024. Therefore its not a fundamentally 'bad' design, something must have changed or broken recently. I do like the look of the Perun Hybrid (with clicker), but I don't want to spent £90+ to find out that isn't the issue.

I've emailed ASCU for the technical spec on the MOSFET, and to see if I can work out how to get to the settings. 

View attachment 138945

 

[GiantKiwi]

I've emailed ASCU for the technical spec on the MOSFET, and to see if I can work out how to get to the settings. 

You probably aren't going to get a response - all of their interactions evaporated over 3 years ago.

 

[jagillham]

Played around with this some more, and might have found the issue. Took the spring, piston, cylinder etc out and connected the grip back to the gearbox without the lower receiver.

When firing rapidly on semi the selector plate moves forward just a touch and no longer connects with the ASCU contacts! Not sure if the selector has worn out a bit over the years (that and the gearbox case are probably about the only original parts), or the ASCU prongs have just lost their spring. I've bent the prongs out a little, but might replace the selector... any recommendations for one that plays nice with a G&P gearbox?

 

[Skara]

Uhm, I don't think such selector plates can be found anymore..

Why don't you shim it so that it stays in place during firing?

If you're really keen on not upgrading to a proper FCU (you have your reasons and nobody can force you) you may give it a "new" life with zero expense.

Btw you should really install the ARL again, seems silly to me to rely on the motor alone to keep the gearbox from spinning the other way, unless you have some sort of uni directional motor, which is not the case since it's a SHS HT..

 

[jagillham]

Is it not just a standard V2 selector plate on a G&P gearbox? I just ordered a SHS one earlier, looked the same to me (albeit the ASCU requires a slight modification to not manually engage the cut off lever). Also ordered a new trigger spring as that seems to have broken on me with all the semi-spamming. A bit of luck it happened whilst I needed to take it apart again anyway rather than during the next game!

I'm not sure if the selector plate is necessarily moving normally more than a minimal amount, and of course the selector cam would normally keep it in place when the gearbox is in the lower receiver. I'm hoping its more a combination of the ASCU prongs being pushed back, some wear on the selector plate copper contact, and the selector plate itself getting slightly out of shape.