AUG Rebuild Can you check my theory.

[Iceni]

Hey I'm starting my Aug rebuild from stock.

The base model is the ASG Aug A3. It it the non mosfet early model.

The work-up is to make a gun capable of using 7.4 lipo's. Be reasonable accurate, Have better than stock range. And be more durable.

The gun itself was purchased second hand. It has a few purchase issues, That will be worked out with the rebuild And this thread is to make sure parts and theory crafting are correct. The work will be done by me. And it will be a learning curve. And issues I will read, re-read, and find information before I make a silly decision and create more problems.


External modifications.

A new shim for the body pin is needed. The ASG original one is bending under stress and doesn't have the spring in the material to hold shape under tension. Meaning the body pin falls out when moved from the locked position. I still have the original so I'll template it out and make a new one with better steel. I have a decent propane torch so I'll heat the steel to red, make the bends, then re temper the steel. Taking it to red quenching, then back to blue. I'll drill it with a diamond ball tool. Should give me the correct level of spring and make a durable part.

Shell sound damping. Either sorbo or car speaker damping. I'm thinking the car stuff might be better as it will give the gun more rigidity whilst damping the gearbox. I'll have to have the shell split to sort this out so I'll use the same product on the magwell to reduce BB's dropping into the body.

The gearbox retention plate needs shimming, and a metal contact strip making to spread load.

Barrel modifications.

From stock, Madbull 6.03 and a Madbull hop rubber. I know there are better hop systems out there but this has to be something I can do without too much effort. These seem like the best compromise on price to performance. And will be replaceable in the field should I do something silly. The hop itself will be polished to have the internal mould lines removed.

Gearbox Electrical.

Because of the lipo and the fact it has already made single shot unreliable I have to do a few modifications here.

Home made NB mosfet (already made). Rewire with 30 amp wire. I need to amp test my motor and see what the total draw is. A future modification may be the removal of the replaceable fuse for an automatic breaker but not atm.

I need to clean and re-bend the single shot truck contacts. Depending on the lipo damage I may have to replace contacts as well. If this is the case I'll template out the contacts and make new ones in thicker brass.


Gearbox mechanical.

New bushings. 7mm Stainless steel with a re-shim.
Silent head and piston. (It slaps pretty hard atm, and the piston and head are more for my ears than anything else!).
Re-grease.
Tooth removal from piston
New spring guide to a metal one.
Polishing of the gear mesh, and casings.
The air nozzle needs new grease, and a check of the seals. I suspect it has no grease, and is giving a poor seal. If I find this to be the case then there are o-ring variants available that should clear up the problems. I understand that the aug is problematic on this particular part.



The gun last chrono was at 270fps. I suspect the air nozzle seal is poor so that will need to be addressed, The single shot is intermittent so that needs fixing. I don't think the gun needs a new spring. I think the low FPS is air leaks. So I'll fix the air problems before I look at a spring upgrade.

I did have a good chat to an Aug man at my local site. He runs 3-4 bodies with 3-4 different set-ups. They all work really well. I didn't get some information I needed from him but he can be called at any time if I need the specialist aug parts. He also showed me a selector mod for the safety that I may implement.

 

[Sitting Duck]

madbull barrel - hold up hmmm, bit overated/priced imho

clean old one and just check bucking first

change barrel n stuff later if needed

but check bucking/replace is cheap

check out semi problem

unsure if she is failing to fire electrics wise - contacts

or mechanically wise - cut off, switch or selector

or varying fps - was a bit vague

fps issue is most likely seals plus possible bucking torn etc...

Silent piston/head - yeah maybe if you wish but stock one might be ok as is

but use a sorbothane/neoprene mix when doing AoE will reduce piston slapping

correcting AoE will drop you 10-15fps so a bearing spring guide will claw it back

good seals yes but check everything once you got box apart

cylinder scratched - replace, polish it using silicone, soak good fitting piston o-ring in it too

ensure piston head has good vent holes - 6 to 8 about 2mm to help seal quickly on release

cylinder head ptfe tape or replace if still not happy with double o-ring type

polishing inside box - don't have to go nutz just ensure the bits that move are smooth

eg: piston rails, tappet, switch itself, cut off lever moves freely etc.....

just time more than money is what works best

money saved can be used for bits n bobs if/when needed after doing a good overhaul/service

eg: new motor or barrel once box and fps is running better

best of luck

 

[BBrotherwood]

My challenge to you would be to adapt the rails and turn it into a proper replica of an AUG A3 rather then the horrendously bad and non existent in real life system the airsoft companies dreamt up.

 

[Iceni]

Thanks for that.

It's defiantly the contacts that are having the problems, I took the gearbox out last night to check. All the trigger does is push back on a block with a spring and den-dent. Even on the naked box you can make it misfire on single shot. It's a common fault on an unprotected lipo, I just wasn't expecting it to show after a couple of games. The Aug having separate contacts for single and auto means it's actually pretty easy to fault find. I suspect when I open the contacts out I'll either have a warped contact or arc blackening. Even if I have to fashion new plates that is not a hard problem to sort out for good. The truck is still working as intended so it has to be the simple fix.

The airseal is another matter. I'll only know once I get it open and can see what the deal is with the internals. It's on the stock white nylon bushings atm so they have to go. I'm not risking them oval-ing and taking out the gears for a £10 modification. Same goes for the spring guide, It would cost me more to replace the other parts if it fails than to just put a more durable on in from the off. I'll have it in bits so I'll pre-empt the failure and replace it before it becomes a problem.

Motor wise the motor is decent enough. It's pushing 23 rps, and I'd actually like it to be slower. She burns ammo without a reliable single shot. The airseal should reduce it a little but I see not point in swapping the motor out when the one I have is more than enough. I did almost 3K bb's last game, and realistically I'd like that to be 1K or lower.

Don't worry about the pricing of parts. I'm not spending more than the gun is worth. I'm happy with the Aug as a gun and system. I like the fact the gun is an open design, The internals have room, the parts are interchangeable without needing anything special, And provided I can get it constant with a decent range I'll be more than happy with the system.

My challenge to you would be to adapt the rails and turn it into a proper replica of an AUG A3 rather then the horrendously bad and non existent in real life system the airsoft companies dreamt up.

I don't think that is ever going to happen. The model I have is an A2 with added bits. The real A3 is 100% different and I don't have the tools needed to cut and lower the top rail, then CNC out a new front end. You can make it look better with the blanking plates but it's still not an A3 it's a tarted up A2. At some point one of the companies might start to produce the correct upper receiver, when that happens the conversion to a real A3 would be possible, but cutting something up just because it ircs you isn't the right way to modify a gun. If the A3 I had bothered me that much I would have got the A1 or A2 wariant to begin with. Those models however have a feature I saw as been a model failure. The front hand grip is a weak point and if the small lugs it attaches to fail then you have an expensive repair (new upper reciever $50 evike) to make the gun right again. The A3 whilst looking wrong can use a more solid front grip and the added sound absorbing materials should rebalance the weight.

 

[Sitting Duck]

Motor wise the motor is decent enough. It's pushing 23 rps, and I'd actually like it to be slower. She burns ammo without a reliable single shot. The airseal should reduce it a little but I see not point in swapping the motor out when the one I have is more than enough. I did almost 3K bb's last game, and realistically I'd like that to be 1K or lower..

if she is doing 23rps on 7.4v that is good mofo neodym motor in there

soz thought she was running on weak ferrite one

 

[Iceni]

I suspect the motor is running fast due to the poor airseal. It doesn't look like the stock motor but it has no branding, I've done the RPS with 2 chronos now and both times it was over 20. My own element E1000 gives 23RPS, the xcoretech on site was saying 21RPS so I have no reason to doubt those numbers. And in a short game the gun will happily eat a 330rnd high cap when only using short bursts. I'm actually thinking I need more 170rnd MAG mags as the 2 I have are simply not enough!

 

[cyrexx]

You have mentioned that the gearbox retention plated is going to be re-shimmed, this may help with the FPS issue as the retention plate hold the gearbox against the hop unit, if the retention plate is not pressing hard enough against the gearbox the gearbox moves away from the hop unit reducing the seal, hence a loss of FPS.

 

[Iceni]

You have mentioned that the gearbox retention plated is going to be re-shimmed, this may help with the FPS issue as the retention plate hold the gearbox against the hop unit, if the retention plate is not pressing hard enough against the gearbox the gearbox moves away from the hop unit reducing the seal, hence a loss of FPS.

I don't think it's touching the top of the box at all. The bottom is locking in well but the plate just drops onto the top seating without any pressure. There are various mods.

The one I was looking at uses scotch pads as a backing material on the plate. They have enough compression to push without affecting the seating angle of the gearbox. The other options involve sorbo. I'll have to be careful with this mod as too much pressure will affect the plates screw mounts and there only small. The problem is how to make any modification solid enough for rough use. I suppose cable ties and shim with a couple of holes would be the simple solution.

Realistically removing those lugs all together and mounting an internal metal system that is bolted to the shells might be better. It's certainly something to think about in the future and provided it is done thoughtfully it should look right. It would involve making some outer plates for over the shell with counter sunk bolts, and then welding nuts to whatever I decide to use inside the shell. Placement of such a system might be problematic with the ejection port baffles on top of the gearbox.

The other thing I may do if the bolt and ejection ports do pose a problem is pick up another rubber port grommet. And remove the baffles from the top of the gearbox. Then upgrade the bolt slide internally. If I don't have to slide back the covers to get to the hop I can make the whole bolt slide more solid and provided it has at least 10mm of travel backwards it will still function to lock the barrel. It'll also sort out the bolt handle wobbling and been a point of failure.

 

[Iceni]

You guys are going to love this.

Stripped the box to have a peek.

It's only got a 50% cylinder in it.... Whacking great hole staring at me. The guy who sold it to me must have had it on the closed side of the box to keep the FPS up for sale lol!

The box looks good apart from that!

 

[Sitting Duck]

ahh that might help if was nearly a full cylinder - say 7/8th type 1 for 400mm

or full type 0 for 500mm....

add cylinder on list coz it ain't scratched

its got a friggin massive hole in it

 

[Iceni]

This is going to open a whole world of pain.

I have no idea what the gun is going to do once it's got a full cylinder in it! I suspect the ROF will decrease by a huge margin as the piston was previously running without any back pressure! So my ROF will go back to where it should be. The FPS will rise, but by what margin is anyone's guess! I'm suspecting the gun will be do hot after this I'm going to have to strip it again and take a trial and improvement method on spring to get it to rights!

I just measured the cylinder that came out. 22mm from the hole to the head. That's an Mp5 cylinder lol! There is no wonder the gun was doing crazy things! How those BB's were not just rolling down the barrel, and how it was getting 270FPS is my mind blown. The only thing I can think is the grease must have been holding back a lot of the air, or the spring is something industrial.

I'm going to have the be very careful when I put that spring back in!

Teeth and piston have already been checked, There both full sized and have been travelling the full length of the cylinder. So that is at least something I don't have to replace.

 

[Sitting Duck]

ya barrel length is 400mm to 500mm

so port will be either port very near back or full cylinder

in anycase the rof shouldn't drop massive coz it was still having to pull spring back all the way ??

(unless it was short stroked a few teeth - the spring still fully compressed)

if you wish - see if you can weigh the complete piston assembly

ideally no bearing to save weight

not an alloy piston head - plastic/pom one

piston can be swiss cheesed a bit but tbh only normally shaves off 2 to 2.5gms

the bearing can weigh more so drop that

if complete piston weighs in under 20gms that ain't bad

lighter piston returns quicker and can help avoid PE and minor slight boost in fps than a sluggish piston

but it is how smooth and how good the little bits n bobs all move and fitted together

that is what makes a good box really

 

[Iceni]

Yeah the spring was under full tension, Teeth all checked both on the piston and the sector gear. It even has a nice final metal tooth on the piston. The whole thing looks like new bar the grease taint so that is good to go back in.

It was the JG piston and head. Flat poly piston head, Poly piston, Counter weighted with the spring lock. I was already looking at the element V3 head set so I'll keep the piston as it was in good general condition, and replace the heads. I'll remove the bearing on that upgrade part as I don't like bearings under shock loads. The element set sits in a good position price wise, and should help with the piston slap as well. I'll lock everything up with threadlock on the rebuild, as for swiss cheesing it I'm not running the gun at a silly ROF so it's not needed. If I wanted ROF then there are better base guns with bigger battery capacities, shorter inner barrels, and less movement on components. Might be a future project building an MP5 or P90 to do that. Been a Yorkshireman by birth BB consumption or rather the lack of it is more of a concern atm. Less BB's of a higher quality on target, Win Win.

With an oem spring that has been using the piston spring lock thingy can I just clip and file the extra bit off the spring or is it advisable just to add an M90 and forget the OEM one even existed. I have a chrono so I can test away, I may also see if My friends have a spare M90 or similar for the rebuild so we can gauge it from a known point rather than an OEM unknown.

Once I get my parts sorted I'll start to rebuild.

This weeks mini project will be the shells. I'll get the trigger blocks out split it to nothing and start to work out where padding can go.

 

[Sitting Duck]

you can use the old spring - cut off the "hook" where it clips onto the spring lock

That metal spring lock can weigh up to 7.5gms - so lose it

The spring will now be compressed about 9mm less than it was originally once removed

correcting AoE will lessen the piston stroke by about 4mm...

but if adding a bearing spring guide then that adds 5mm to spring's starting spring compression

(so AoE & bearing spring kinda cancel each other out - soft of)

BUT you will still be that spring lock's 9mm out so think the old spring will be ok

(might have been a m100/110 poor seals/port plus if been there a while lost a bit of power as all springs lose a bit over time)

you can use a std spring guide if ya that worried and if say only shooting 300fps

then adding a bearing spring guide after testing will bring up fps by aprox 15fps

Alas you can try to use Mr Spock's best calculated vulcan "guess" in the whole universe..

but at the end of the day the real test is when you simply

"suck it & see" as so many many variables to predict even 99% accurately

 

[Iceni]

Right I've picked up some grease. I got 125ml for £5.99.

http://weldtite.co.uk/products/detail/cycle-grease-with-teflon-tube-150ml

I'm soaking some O-rings in it now to check for any swelling or embrittlement. As far as I can tell it's a mineral oil and teflon based formula. So it should be good for gears and safe with nitrile o-rings, Definitely not safe on rubber o-rings tho.

The reason for going to a racing bike grease is simple. It meets a lot of the criteria for airsoft, whilst also have a big industry that has plied research and money on the problems they face. The grease they use for the gear cassettes, wheel bearings, and cranks has to work well. Has to have low friction but also stick to steel, Needs to be highly water resistant, And has to function at great speed.

You don't always thing about cycle mechanics but a racing bike at 40Mph is doing 18M/s on a 70c rim that's about 9 revolutions a second. So racing grease is good stuff.


I've also picked up the padding for the shells. I couldn't get the self adhesive type without putting it on order, but I found some nice mid desitiy floor matting, It's about 3mm thick and has a woven inner core. And some industrial grade double sided tape. I'm going to start cutting and fixing it later this week.

 

[Iceni]

Right little update.

I stripped and rebuilt the gearbox. (several times!)

New full cylinder, m90 spring, shims, Silent head and piston head, solid brass spring guide.

On the m90 the gun is shooting 295fps. It's right where it is expected to be since it's running without any spacers on the piston or spring guide. And the new spring guide is a lot thinner at the base. The spring guide came with a plastic 5mm spacer, and there should be a bearing on the piston head that looks to sit very proud, Had I left them in the fps could be up to 320-330 ish. I may test this because 330 is ideal for me. I may get some stainless rod and make some spacers so I can dial the m90 to spec.

The single shot has been stripped to the contacts, removed from the gearbox, it's had the trolley polished and cleaned. When I rebuilt it the contacts were out by a fair margin so they got fettled. I also dropped the auto contact to be a touch lower, and filed the housings and trigger stop so full auto has more in-swing and a larger distance between single shot and auto.

I've ground the safety to add a single shot setting.

Padded some of the internals. The larger side walls, the sides of the magwell, the rear pressure plate and the handgrips. On rebuild this has removed a fair bit of noise but there is room for improvement. It's also 100% fixed the play in the upper receiver, and made the body pin a lot tighter.

The body pin has had the top leading edges filed, This makes it push better when you slide it to a locked position.

So far the gun feels 100% better, single shot is working well, and is selectable. The gun is pretty consistent on the m90, and it's not slapping so hard. The padding wedged into the handgrip has reduced a lot of the vibrations (I did both the front guard and handgrip). I've also removed one of the dendents from the trigger to make the auto setting smoother now that single shot can be isolated.


Jobs left:
Rewire with 30 amp multicore and the mosfet.
m90 spring tuning.
More padding.


My bike grease is working well on the gears, but I got some frog lube for the cylinder. The only thing I've broken is the dust cover under the trigger. I figure that bit is mostly for Ak's that have an open trigger at that point so I may not even replace it.