Sewdhull

The key to a dmr is a good hop and airseal so you can send heavy bbs consistently. You don't get range from fps alone, you'll lose most of that BB speed advantage in 30m.

There are 2 types of MOSFETs. The type that prolong the life of your trigger contacts by doing the switching of the power to your motor and the type that add features to your gun, which also prolong contact lifespan. The former should be fitted to all guns in my view as the contacts for Airsoft guns are not very good and are the same as when everyone used nimh batteries with lower current outputs. You will get more power to your motor and a way longer contact lifespan.

Filling a pressurised container from another pressurised container requires that there is a pressure difference. All that purging will do do is reduce the temp of the magazine allowing the gas to transfer, because the pressure reduces in the mag. There is some small temperature reduction from general filling which is soon offset by the valve spring requiring a bit more pressure. Liquid to liquid transfer does not alter the temp. With cooled magazines i have never had issues filling them. Its hard to know how much gas a mag will hold. It would be useful to know. If you do something expecting an improvement you will probably see one...

Glass is pretty flat, good enough for our purposes. There's no friction reduction to be had since friction is independent of area, the high points produce no more friction than if the load was spread over the whole shim. Our gearboxes are not precision machines, we can shim to 100 microns, were using plain bearings, with mediocre gears and unknown manufacturing tolerances for anything. Anything we do like this is because we like to fettle. Breaking in a gearbox is not something I've ever done, only the bevel gear could wear and offer a chance to correct the wear and that only between the motor pinion and bevel gear. Gearboxes have slack right from the outset, gear backlash, bearing to shaft gap, gear end float etc. It's not put together tight like an ICE for example and run in. Maybe that's something to try, build it tight and run it at low load until its not tight any more... Sure is fun to fettle tho.

I would carefully observe the movement of the tappet plate and see what the timing looks like. If it is fully forward in good time before the spring is released and stays there a bit before being pulled back by the sector gear, then you should be looking at the nozzle interaction with the bucking, some buckings are shorter or longer than others at the nozzle end. Since the nozzle and tappet plate are original then I would not expect the tappet plate to need any adjustment, unless the new cylinder head has pushed the nozzle and tappet plate forward causing fouling on the case. The tappet plate and so the nozzle should be able to go as far forward as before the changes were made in any case. Except perhaps if the cylinder head was off center for some reason. You do have a new sector gear so this may affect the timing and movement of the tappet plate, potentially preventing full forward motion against the spring tension. Where did you remove the teeth from on the sector gear? Removed what lip on the bucking? Oh and how well does the nozzle fit on the new cylinder head?

Where did you find the SEF receiver? I can't recall seeing one and I mooched around MP5s for ages before buying one.

Filing the grub screw down doesn't need any disassembly other than that shaft. My grub screw was rubbing plastic from the handgrip plastic. You do need to take the plastic grip off to do the rest. Gearbox is untouched. The slots can be filled with JB weld etc as the locking tabs are plastic. I haven't done it yet tho. I'll take the part down to metal and put tape on it to make a mould to put the epoxy in. I have a full stock which I might use instead since the collapsible stock has limited utility.

First thing was pull the lever out, there's a grub screw on the left to undo and then pull the lever out. There's another grub screw holding the lever to the shaft and this was sticking out too far and interfering with the body. Had to file it flush. It's locktighted in so I couldn't remove it. This helped but I had more. I made the mistake of looking at some of these falling down an internet rabbit hole and ended up hanging my nose over the gun in the title. Of course I then bought one and following are my thoughts on the gun. In case you don't know what it looks like... https://images.app.goo.gl/9mtVnfitABNswYUX6 For me it's a sexy gun, maybe the sexiest. Sexy and heavy. It weighs 3.6kg with mag, battery and sight and more than a little front heavy. It's the Blue version, so inside it should have half decent bits and clearly the air seal is ok, firing at 365 fps on a .2g BB, through its little 220mm barrel. It's happy on a 3S lipo or a 3S life. I swore to myself I would use it before taking it apart, but I didn't. It had a very clunky fire selector which bothered me greatly so I pulled off the sliding stock, which is very nice and sturdy, with a great extending action (only 1 of the 3 extended positions is useful to me, so I will mod those later) Once the body pin was out, I slid out the gearbox out and pondered the fire selector. I am used to a G36, they are V3 gearboxes and this is a V2. I don't recall working on a V2 before so of course I ploughed ahead, pulling the motor out and sliding the plastic bits off after taking the fire selector levers off ( grubscrew on the left, then pull the shaft and right selector lever through the gearbox. There's a "plastic bit" that sits in the plastic lower, through which the selector shaft passes from the right and gets sandwiched by the right selector lever. Anyhoo, the gearbox has a quick change spring, a shiny ribbed cylinder and a plastic nozzle, sans o ring. The casting is textured for some reason, it's not radiused and not shimmed properly. I noted that the plastic fire selector plate was binding leaving safe to semi on the contacts, which stuck up really high, so the copper part of the fire selector plate had a lot of work to do to get past them. I imagine it's meant to electrically disconnect the trigger as well as mechanically lock the trigger on safe, but it doesn't do the electrical isolation. I will probably rewire this given the pointless contacts. The fire selector plate and the aforementioned "plastic bit" ( a sort of cam) work together provide a crude detent, in addition to the detent in the left fire selector lever, when selecting safe, semi and auto. For safe the plastic bit has kind of beak that goes over centre on the bottom of the fire selector plate, on semi there's a nub on the plastic bit that nestles against a raised bit on the fire selector plate and on auto, the aforementioned beak engages the raised bit. To smooth all this out required: Pushing the contacts down ( they may have been incorrectly seated) so the fire selector plate would move more freely Taper the beak of the plastic bit, so it would engage safe with less force and move from safe to semi with less force. Reduce the size of the nub on the plastic bit to engage semi from safe more smoothly. Taper the top side of the beak so it would more easily engage in the auto position. There is still a detent effect putting the fire selector plate in the right place, which now works with the fire selector levers own detect, meaning it all clicks into place now. Much like my G36s. Having, as previously mentioned, sworn to not take this thing apart I now have a list of things to do. Spring change, maybe nozzle change. Shimming and consequently adjusting motor height. Filling in the 2 useless cut outs in the sliding stock so it slides to the right position. Add a MOSFET ( nothing fancy, I have a load of 3034 chips to use) Some of the MOSFETs used in the posh ETUs are really not very good. Altho the Jefftron ones are very nice. Rewire the thing in decent cable (the PVC stuff doesn't like the bends this gun seems to require and it uses lot of it, going to the back of the gun from the gearbox then to the front to the battery) Short out those weird contacts under the selector plate and get the copper off it. That's probably enough for now, please feel free to tell me where I'm going wrong or what else I might do since I am already doing this ^^^ Maybe you've noticed there are not many pics, Some tech issues prevented them appearing here. I'll add them as soon as I can. https://airsoft-forums.uk/topic/57368-cyma-mp5-sd6-thoughts/?do=findComment&comment=493052

I got the sd6 version, nice gun. Had to fettle the selector tho.

Don't need another wire to monitor battery voltage, maybe it's for trigger positive

Check the short stroking hasn't messed with tappet plate timing and all the above from SeanM

Yoga, do it.

I wonder if the only thing that really matters for gas usage is the spring that whacks the mag valve, or the valve spring itself. Other stuff will affect how much of that gas gets to the BB. Thoughts?

Watch alot of you tube if you are a visual learner. Get a gun to strip and see how it all interacts if you want to learn that. You'll find forums like this have lots of info, but also search for general how it works type stuff. Pick the type of gun you have or want and get to understand it.

It's fine because it's given not sold, which is where the law comes in and the conditions apply.

The ngrs has an mr30 connector? That's interesting and bizarre. You want a decent sized bit and good wattage for these types of connectors, plug a spare connector into the other end that you are soldering incase you overheat it.

Here's a selection of my batteries, Airsoft at the bottom. They have all been bought for different applications, the 2 big green ones are spares for large drones I've built in the past, some for electric planes. The big ones were used in pairs and didn't need a high C in the large drone they were used for. The 2 batteries supplied 200A. When I came back Airsoft, Hobbyking had stopped trading so I got some of what was on offer, it wasn't good . The green 2.2s are 30C and 40C 11.1s, they might fit in a stock. The .95 nanotech is for an aep, I have one with the pack split to fit. It's a 25C battery. Just incase anyone's interested.

That battery is 15 GBP from techshop. I don't think it's about reliability. Airsoft doesn't need the great performance drones do, but there's no excuse for the offerings in Airsoft at the price they are offered at. I suppose it's because people buy them.

Here have a look at this battery. https://www.quadcopters.co.uk/lipo-batterys/3s-lipo-batteries-111v/tattu-1550mah-111v-3s-75c-lipo-battery-2114 I'm unsure why our Airsoft batteries are so poor. I realise it's out of stock.

Yeah I understand, I wasn't clear. It's not as frequent as auto fire for example, but the loads will go from zero to 100% as the drone races around. Batteries only last 3 or 4 minutes. Our Airsoft batteries are pretty poor by comparison.

Your wish etc http://www.airsoftlab.eu/docs/experiments/motor_current/

Vapex and Nuprol packs look the same, because the voltage is lower motors won't pull as much current from a 3S life Vs a 3s lipo or lion. However I haven't used the life's much, as I just have the one for testing. I'll measure some of my batteries and let you all know what they are like.

Even those little drones draw some mighty amps at fully throttle as they whizz about. You'll see 70C or even 100C packs being used. There's some tests online you can Google. I use xt connectors, because they are better so I don't need to repurpose anything, Nuprol do some life packs, I have one and it's fine. https://www.tactical-clothing.co.uk/product/nuprol-np-power-1100mah-99v-20c-li-fe-slim-stick-type-battery-216629?gclid=CjwKCAiAjfyqBhAsEiwA-UdzJDECrsOk5S3L-TZEarDw3YC1QjQkIYJuQ9zcAi3Kpuk0A0wBlpJ8LBoCUkEQAvD_BwE

For gas efficiency a weak recoil spring seems logical as the striker ( the thing that presses the mag valve)gets reset when the bolt travels back and the spring resists this. The nozzle spring shouldn't make any difference to gas usage, it's purpose in life is to pull the nozzle out of the way so it can return and scoop up another bb for the next shot. Only when you are getting high ROF will a stronger spring help there, maybe if you have short stroked it and or added a stronger recoil spring, then its about timing. I was thinking earlier today how poor the seal is between the recoil piston and it's cylinder( nozzle) is and how to improve that. It should speed up the recoil and perhaps reduce gas consumption, cos I know mine chucks out a lot of gas at the end of the barrel. Way too much gas per shot I feel.

Drone currents vary by a magnitude compared to airsoft. We either have semi or auto. Semi draws more power for a shot, requiring more current as the motor starts from 0 RPM. Auto is a varying load for sure but cells don't mind that if it falls within their specs. For sure mAh rating is less useful than the current the battery can supply, and you'd need to do power calculations to estimate battery life. Way easier to get a pack and see how long it lives ( For me it only needs to last half a day, I can change it at lunch. For me, I use the largest batteries (physically) that will fit in my gun, current being more important than capacity. I have a couple of watt meters so i can see what my load is and therefore what type of cells I can get away with. My preference is Lithium iron Phosphate (Life), then Cylindrical cells, then Lipos. When I flew drones weight was an issue so they are all Lipo. I have some enormous packs, now in ammo boxes. I'm leaning towards 12.8v Life packs if they will fit, because they are so forgiving in use, last a really long time and supply good current, the voltage not being as high as the 12.8v 4 cells would give you because as we have seen in tis thread, voltage drops quickly and stays at a level for a good while before the battery is exhausted. However, often there isn't enough room for such luxuries.