Refurbishing a €20 AEG – Part 2

Having worked out what I have bought and fixed the loose stock, it’s time to try to work out why my €20 AEG won’t shoot. It didn’t come with batteries, but when I tried fitting the battery pack from my Umarex G36C, nothing happened when I pulled the trigger. The 7.4v Umarex battery is less powerful that the recommended 9.6v battery for this King Arms replica, but even so, it should operate. Clearly something is wrong.

I have to admit that I hate working with anything electrical. I have restored a fair number of elderly motorcycles over the years, and the bit I always dreaded was trying to sort out electrical gremlins. The crisply lined wiring diagrams never bore much resemblance to the rat’s nest of mismatched wires and soggy insulating tape that I found under the tank of most bikes. However, here I’m happy to report that the problem is fairly obvious, even to me.

The battery lives inside the vertically split front foregrip. To remove it, the sprung rear plate is held down and then one or both halves can be lifted off. Looking closely at the end of the Mini-Tamiya connector reveals that the wires have been fairly crudely bodged into the metal connectors. A couple of strands of one are even touching the other wire, clearly causing the connection to short-out.

It doesn’t take long to remake new, neater and more effective connections. I plug in the battery pack and it shoots in both semi and full auto modes. Hurrah! I haven’t yet tried it with BBs, but this AEG is certainly operational now.

Cosmetics

There is nothing else terribly wrong with this replica (and the red-dot sight works too – it just needed a new battery!) so all that’s left to do is to try to make it look a little better. I begin by stripping it down. To do this, you only need to remove a single pin, arrowed below.

This then allows the barrel assembly and upper receiver to be slid off to the front, being careful to guide the battery wires into the trough in which they sit.

The inner barrel and hop up can then be slid out to the rear and the inner plate that covers the ejection port can be removed.  

This disassembly probably isn’t essential, but it does give me a chance to check the internals. Nothing seems to be obviously broken or worn, the inner barrel looks straight and in good condition, the hop-up works as it should and I can’t see any other issues. It’s now time to start thinking about how to improve the way this rather tired AEGs looks. There is a fair amount of corrosion on metal parts including the ejector port cover, the handguard front plate and the collar that stabilizes the buffer tube.

All the metal parts are removed, sanded to remove rust and sprayed with a can of acrylic satin black that I have in the shed.

Then it gets cleaned thoroughly in warm water with a little washing-up liquid in it. This also gets rid of all the stickers. Finally, I go over all the plastics with a little silicon spray. When it’s dry, this helps to restore the faded plastic to its original black colour. Below you can see the two halves of the front handguard, on the left, after this treatment and on the right, before.

It may not be particularly obvious in this photo, but in real life, the difference is quite dramatic. All the plastics get the same treatment.

Then, it all gets reassembled. And I’m quite happy with how it turned out. It’s surprising just how much difference careful cleaning and touching up the rusty bits makes. This elderly M4A1 isn’t perfect by any means, but it is significantly better than it was.

The last stage is adding the carry-handle and rear sight. This replica didn’t come with either – it was fitted with a Swiss Arms red-dot reflex sight that I have decided to use on my Umarex G36. However, I was very happy to discover that it’s fairly easy to find replacements – I was able to source a generic Gexgune M16/M4 airsoft carry-handle and rear sight on Amazon for under €15.

It’s nicely made, fits well, incorporates elevation and windage adjustment for the rear sight and it matches the colour and finish of the rest of this replica. With this in place, it’s finally time to try some shooting.

Shooting

After all this work, I’m keen to find out how well this elderly AEG shoots. And the answer is: very nicely indeed! It has much more power than my Umarex G36C and it’s more accurate too. The Umarex AEG isn’t bad, but it does produce occasional flyers than hit the target at anything up to 2” from the main group. This one produces tighter groups at the ranges at which I shoot and the adjustable rear sight means that I can get the point of aim and point of impact to coincide.

The result of around 50, 0.2g BBs, from 10m in a mix of semi and full auto.

Problems? Well, very occasionally the trigger seems to jam in while in semi-auto mode, but flipping it to full-auto and back fixes this issue. The spring that retains the collar at the base of the handgrip seems much too powerful. Pulling it down to remove or replace the upper handguard halve takes a lot more effort that I’d have liked. And the Hi-Cap magazine rattles like a maraca when it’s full of BBs.

That’s about it really. I really don’t like peep-sights, but that’s just what you get with an M4 and I can always replace the iron sights with the red-dot sight I got when I bought this. The rate of fire in full-auto is fairly slow because I’m using the 7.4v battery from my Umarex AEG rather than the recommended 9.6v. However, I don’t find that a problem at all and, to me at least, this slower rate of fire sounds and feels more realistic than the rapid “Brrrr…” that some AEGs produce in full-auto.

Conclusion

I was nervous about buying an old AEG that wasn’t working, but relieved to find that refurbishing it was fairly simple and no more complicated than working on any other replica. I have enjoyed this project and I have even learned a little about how AEGs work, which can’t be bad. In addition to the initial price of €20, the only cash I spent here was on the new carry-handle/rear sight assembly, and even that was easy to find and relatively cheap. I could buy a more powerful battery and charger and replace the Hi-Cap magazine this came with for a Low or Mid-Cap, but do you know what? I don’t think I’ll bother. I’m quite happy with it as it is and I plan to just enjoy shooting it for the moment.

For not a great deal of effort I have ended up with a functioning AEG that’s fun to shoot and doesn’t look too bad as a replica of the iconic M4. This King Arms M4A1 has good weight (just over 2.9kg with batteries and the carry handle in place), looks convincing and shoots well. For a total outlay of just €35, I’m happy with the result of this project. If you are offered an old AEG that needs a little TLC and you’re willing to put in a little effort, perhaps it might be worth considering?

Happy shooting  

Related Posts

Refurbishing a €20 AEG – Part 1

Umarex H&K G36C IDZ

Refurbishing a €20 AEG – Part 1

You don’t get a lot for €20, especially not in the world of replica guns. So, when I visited a boot sale recently and discovered a man with (literally) a plastic bucket filled with half a dozen or so well-used airsoft AEGs, I was immediately interested. All of them showed signs of hard use with rusty fasteners and cracked and broken plastic. But one caught my eye. It was a replica of the iconic M4A1 that had good weight, everything seemed to be there (including the magazine), the plastic parts were in good condition and it was fitted with a simple Swiss Arms reflex red-dot sight in place of the carry handle.

However, it lacked batteries, the buffer tube and stock were flopping around loose and appeared to be retained by a great deal of black insulating tape, the red-dot didn’t switch on and when I asked if the AEG was working, the answer was, “probably”. And a  smiling shrug.

I asked how much? He said €25. I offered €20 and he agreed. So, I unexpectedly found myself the owner of an AEG of completely unknown provenance. There was nothing on it to suggest who it was made by and no certainty that it worked at all. But hey, for €20 at least I’d have a red-dot sight that I could use on my Umarex G36C. Probably… Let’s see if I bought some cheap fun or an expensive source of spares for my other replicas.

The M4A1

Back in the early 1950s, the US Army began a truly futuristic project to develop a totally new infantry weapon. The SPIW (Special Purpose Individual Weapon) was planned as a fully automatic rifle that would fire not conventional rounds but steel flechettes at an astounding 2,300 RPM and from a weapon weighing only 3lbs. However, the project was dogged with problems and in 1964, the US Army instead adopted a modified version of the  ArmaLite AR-15 assault rifle as an interim solution until the SPIW was ready.

The futuristic Springfield Armory SPIW. It never got beyond the prototype stage.

The AR-15 became the M16 in US Army service, just in time for major American involvement in Vietnam, which didn’t work out terribly well at first. Early M16s, particularly when they were used in the heat and humidity of Vietnam, proved susceptible to corrosion and frequent jamming. Eventually, these problems were addressed and the M16 became the principal infantry weapon of the US Army when the SPIW project was finally dropped.

A US Army soldier in Vietnam with the then-new M16

The M16 finally proved to be reliable and effective, but it was always intended as a full size infantry rifle. However, Colt (who had purchased the rights to manufacture the AR-15) also later produced a carbine version, the CAR-15, which featured a telescoping stock and a 14.5 inch barrel compared to the 20 inch barrel on the M16. Initially, the CAR-15 was issued to crews of armoured vehicles and helicopters, where its reduced size made it easier to store and use.

A US Special Forces Delta operator with a CAR-15 during the First Gulf War in 1991

However, several US Special Forces units also began to use the CAR-15 and discovered that the slightly reduced muzzle velocity provided by the shorter barrel wasn’t a major issue. Soon other US military units became interested in this handy carbine version of the M16. Before long, it was adopted by the US military first as the M4 Carbine (with semi and 3-round burst modes) and later as the M4A1 with semi and full auto modes. Experience in Iraq and Afghanistan proved the worth of this weapon and now, variants of the M4 are used by most US Army and Marine Corps units.

US Marines training with M4A1s

First step – assessing the problems

Three functional problems were immediately apparent on examining this well-used M4A1 AEG. First, the buffer tube was loose, allowing the stock to flop around. In an effort to fix this, the previous owner had wound a great deal of black insulating tape round the base of the buffer tube, but this didn’t really address the problem. Second, when I got home and tried fitting a battery and pulling the trigger, nothing happened. Third, the red-dot sight didn’t work. This last issue is a real problem as this didn’t come with the M4 carry handle that incorporates the rear part of the iron sights, so I need to get the red-dot working.

In addition, there are a number of cosmetic problems. Almost all fasteners and metal parts such as the buffer tube collar, the ejection port cover and the front of the handgrip are lightly corroded. Most of the plastic is faded and grubby and there are stickers and the remains of stickers on the receiver. If it’s going to look half-way decent, all these things will have to be addressed. On the positive side, the receiver is in generally in good condition and none of the other plastic parts are cracked, broken or missing.

Finally, I have to work out what I have bought. I can’t see a manufacturer’s name anywhere on this replica. The receiver is heavy plastic with nicely engraved Colt markings and the battery fits inside the handguard which is split vertically. The magazine release and telescoping stock work as per the original and the charging handle retracts, though all it does is open the ejection port to give access to the hop-up adjustment. The forward-assist on the right side of the receiver moves, though the spring-loaded button doesn’t do anything.

The whole replica, with magazine but without batteries or BBs, weighs just over 2.6kg. After a great deal of looking at photographs of AEGs (the M4 and its variants must be one of the most common AEGs), I believe what I have here is a King Arms M4A1 Ultra Grade. King Arms are a Taiwan-based manufacturer of airsoft replicas and accessories and this particular replica seems to have reasonable reviews which makes me think it’s worth trying to refurbish.

Fixing the loose buffer tube

The first job is to fix that loose buffer tube and stock. After removing yards of black tape, nothing is obviously broken which is a good thing, but the base of the buffer tube and the adjustable collar aren’t sitting firmly against the rear of the receiver as they should.

All that insulating tape wasn’t actually doing much… You can see here the gap between the base of the buffer tube and the rear of the receiver and that the buffer tube can move from side to side. The screwable collar on the buffer tube should be flush with the plate on the rear of the receiver.

The plastic stock is removed by pulling the adjustor down all the way and sliding the stock off the end of the buffer tube. This then reveals an end-cap that is secured by a small hex screw. 

Looking down inside the buffer tube with the end cap removed reveals a cross-head screw. Unscrewing this allows you to remove the buffer tube.

With the buffer tube and retaining screw removed, the problem is clear.

Someone has replaced the retaining screw with one that has the correct thread but is much too long. You can see where they have tried to force the blank part of the screw into the threaded part of the receiver. When this hasn’t worked, they simply wrapped a length of insulating tape round the base of the buffer tube to hold everything in place. Happily, this bodging hasn’t damaged the thread in the receiver and simply swapping for a screw of an appropriate length fixes the problem completely.

Well, that was easy! If the rest of this refurb is as simple, I’ll be very happy indeed.

But, in the next part I’ll be doing something that I don’t enjoy at all when I take a look at the electrical side of things to try to find out why this AEG won’t shoot.

Related Posts

Refurbishing a €20 AEG – Part 2

Refurbishing a Crossman Peacemaker

How to make your BB shooting replica more accurate

I like BB shooting replicas.  The use of BBs makes it possible to replicate the function of semi-auto firearms more accurately than is possible in replicas that shoot pellets.  However, I find it frustrating that so few BB replicas shoot well.  One of the first replicas I owned was a Tanfoglio Witness, and I loved its heavy weight and the way it felt just like a cartridge firing 1911.  But I found it irritating that, even at six yards, it scattered BBs over a 5” circle.  Given that current replicas are generally well made, surely they can be made to shoot with a little more accuracy than that?

The main problem here is consistency.  Pellet shooting replicas are good at sending pellets on a very similar trajectory every shot, leading to satisfactorily small groups.  BB shooters are affected by tiny imperfections in BBs and the barrel which leads variation in the trajectory of the BBs and larger groups.  But there are things you can do to make your BB shooting replica produce smaller groups.

How does it all work?

The first thing to consider is what happens when a pellet or BB travels down the barrel of an air or airsoft gun.  A .177” pellet (or a .177” lead ball) fits tightly into the barrel of an air gun and is squeezed against the rifling on the inner surface of the barrel.  When you fire the gun, gas pressure builds up behind the pellet until this is sufficient to overcome the friction holding the pellet against the sides of the barrel.  When the pellet starts to move forward, the rifling also causes it to spin.  When the pellet leaves the end of the barrel, it continues to spin, improving stability.  The friction caused by the pellet being squeezed against the sides of the barrel is the reason that pellets always leave the barrel with less speed than BBs.  The accuracy (or otherwise) of your pellet shooting airgun is largely dependent on how accurately the barrel was made in the first place and how much the rifling has eroded over time.  A build-up of deposits on the rifling can cause some minor degree of inconsistency in the flight of the pellet (though some lead build-up can actually improve accuracy), but generally the most important factor is how straight the barrel is in the first place.

Shooting a pellet in a rifled barrel

Now let’s look at what happens when you shoot a BB through a smoothbore barrel (I’ll talk about shooting BBs in rifled barrels in a moment).  And it doesn’t matter whether we’re talking about a 4.5mm steel BB or a 6 or 8mm plastic BB, the mechanics are the same.  The BB does not fit tightly inside the barrel.  A typical 6mm airsoft BB for example, is actually around 5.95mm external diameter while the barrel on most modern airsoft guns is anywhere from 6.04 – 6.08mm internal diameter.  So when the gas is pushing the BB down the barrel, some leaks past the BB and forms a thin layer of gas between the BB and the inside of the barrel.  Because of this, the BB doesn’t actually touch the sides of the barrel at all and this thin layer of gas actually helps to stabilize the BB and keep it travelling straight.

Shooting a BB in a smoothbore barrel

There are couple of things to think about here.  First, barrel length.  It takes time for the BB to stabilize on the layer of gas.  When it first enters the barrel, the BB tends to bounce off the inner sides of the barrel, especially if it hits a hop-up rubber on the way.  After it has travelled some distance, this bouncing is dampened down and the BB stabilizes in the centre of the barrel.  There is some argument about how long a barrel must be in order for the BB to stabilize fully, but most people seem to agree that anything less than around 70mm (a little under three inches) is unlikely to allow the BB to stabilize completely.  In general terms, the longer the barrel, the better stabilized the BB will be when it leaves the muzzle.

The second thing to consider is hop-up.  Most airsoft guns and some steel BB shooting guns have hop-up.  This is a rubber nub inside the barrel and close to the breech.  The nub is located on the top of the barrel and projects inside.  As a BB travels down the barrel, it strikes the rubber nub which causes it to spin backwards.  This backspin helps to overcome the force of gravity and allows the BB to maintain a flatter trajectory after it leaves the muzzle.  On many guns, the amount which the nub projects into the barrel (and therefore the amount of backspin) can be adjusted.  Most people will tell you that the effects of hop-up are not evident at ranges below 10m, but I haven’t found this to be entirely true.  Even when shooting at 6m, I have found that adjusting hop-up can affect the vertical point of impact of BBs by an inch or so.  However, hop-up initially de-stabilises the path of the BB through the barrel.  So, on a gun with hop-up, it may take more distance for the BB to stabilize.

Hop-up nub inside the barrel of 4.5mm ASG CZ75

OK, now let’s talk briefly about shooting steel 4.5mm BBs through a rifled barrel.  Some pellet shooting guns can also fire steel BBs.  Many manufacturers and some suppliers talk about .177” and 4.5mm as if they’re the same calibre.  They are not – a 4.5mm steel BB is notably smaller than a .177” pellet.  If you shoot a steel BB through a .177” rifled barrel, it is not large enough to engage with the rifling.  Instead, just as in a smoothbore barrel, it floats on a layer of gas in the centre of the barrel.  However, the flow of this layer of gas is much less stable than on a smoothbore barrel because of the rifling which causes it to swirl and tumble.  Also, as it initially enters the barrel and bounces off the sides, the hard steel BB can cause erosion and damage to rifling over time.  A BB will always leave the barrel travelling faster than a pellet because of the lack of friction, but in my experience, I have not come across any replica air pistol which shoots BBs accurately though a rifled barrel.  The higher speed at which BBs travel is unimportant and because of the lack of accuracy and the possibility of damaging rifling, I’d suggest that you shoot steel BBs only in guns which have smoothbore barrels and only shoot pellets or .177” lead balls in those which have rifled barrels.

Left, shooting eight .177” pellets from a replica with a rifled barrel (in this case, an Umarex H&K P30) at 25 feet, aim point is the centre of the black circle. Right, same replica, same range, same aim point but this time using eight steel 4.5mm BBs. As you can see, the steel BBs give notably less accuracy.

How to improve things

Right, so, now we know how it all works, how can we make our BB shooting guns more accurate?  If we’re talking about airsoft guns, the first thing many people think about is a tightbore barrel.  As the name suggests, these are aftermarket barrels which have a smaller internal diameter than the original.  That sounds good in theory, but I’m not totally convinced.  The critical thing that determines how straight your BB will travel is how well the BB stabilizes inside the barrel. Part of what determines this is the size of the layer of gas between the outside of the BB and the inside of the barrel.  Too big a layer is bad and can cause the BB to be unstable.  But, too small a gap is also bad and can prevent the BB from stabilizing fully.  If you do fit a tightbore barrel, you can expect to see your replica shooting with more power – less gas is lost round the BB and so more is available to propel it down the barrel.  However, I suspect that most accuracy gains which users report after fitting these parts come as much from improved tolerances in the manufacturing process used when making these aftermarket barrels compared to the processes used in creating the original barrel as from the tightness of their bore.  An expensive aftermarket barrel may be straighter than a more cheaply made original part (though there is no guarantee of this) but if the bore is too tight, it can actually make consistency worse.

If you don’t want to buy new bits, what else can you do?  Well, there are two things that affect the way the BB travels down the barrel. The first is the quality of the BB itself.  The layer of gas between the BB and the barrel is very thin – around 0.05mm.  That’s equivalent to about the width of two human hairs.  So, any tiny imperfection in the BB which is spinning after hitting the hop-up rubber can cause instability in the flow of gas and may cause the BB to move erratically in the barrel.  The closer to being perfectly spherical that your BBs are, the more consistently they will shoot.  If you can see seams or other moulding marks on your BBs, they are obviously not going to perform well. 

This is a pair of cheap and very nasty Chinese 6mm plastic BBs with clearly visible seams and moulding marks.  Very few 6mm BBs are this obviously crap, but no matter how good your replica, it’s never going to shoot consistently with poor quality BBs.

However, even if they look glossy and smooth, not all BBs are equal.  In general, you should avoid brightly coloured or transparent BBs (especially those which have visible bubbles of air inside them), any small packs of BBs which are supplied with an airsoft gun and any BBs which are not identified by weight.  Most BBs which are made in Japan are good as are the majority from Taiwan.  In my experience, Chinese BBs can be of comparatively poor quality and should generally be avoided.  Just because it says “Precision” or “High Quality” on the packaging is no guarantee that BBs are good.  Be prepared to try different brands and pay a little more for quality plastic BBs and when you can, choose those from manufacturers you recognize (Guarder and KWA, for example, produce very high quality 6mm BBs).

Hopefully, it’s also obvious that re-using plastic BBs isn’t a good idea. The plastic used to manufacture 6 and 8 mm BBS is fairly soft, so they tend to develop flat spots when they hit a target. This of course makes them unstable if you re-use them. While we’re talking about plastic BBs, it’s also worth thinking about weight. In general, the heavier the BB, the more stable it will be and so the smaller groupings you’ll see. You may have to experiment with different weights of BB to find one that works best for you, but the table below gives a general guide to the most appropriate weight BBs to use in your replica. The fps figures are based on the speed when shooting with standard 0.2g BBs.

Under 300 fps: 0.12g

300 – 350 fps: 0.2g

350-400fps: 0.25g

400-450fps: 0.28g

450 – 500fps: 0.36g

Over 500fps: 0.43g

I haven’t found the same variation in quality with 4.5mm BBs.  Most steel BBs from the big producers seem to be of very high and consistent quality with few blemishes or imperfections whether they say Blaster, Umarex, Crosman or ASG on the pack.  I tend to avoid steel BBs from unknown manufacturers – there are Chinese steel BBs around and though I haven’t tried them, I’d probably like to keep it that way.  I don’t use copper coated BBs because I find that they leave deposits on the inside of the barrel, though I know that many other shooters use them without problems.  I also don’t use lead balls in guns with smoothbore barrels intended for steel BBs either.  These lead balls are slightly larger than the 4.5mm steel BBs and they are often not perfectly spherical (or even if they start out that way, the soft lead can deform as they move through the feed system).  They also tend to leave deposits on the inside of the barrel. Lead balls are fine in rifled barrels, but generally not good in guns with smoothbore barrels.

The second thing that affects the way in which a BB travels down the barrel is the cleanliness of that barrel.  On a smoothbore barrel, any tiny speck of dust or other contamination on the inside surface can cause disruption to gas flow which will affect BB stability.  I have found that cleaning the inner barrel is the best way to quickly improve groupings and to reduce the number of flyers on any BB shooting gun.  Even a new replica will likely have traces of packing grease inside the barrel.

Cleaning the inner barrel is very simple.  Remove the barrel if possible, or at least dismantle the replica so that you can easily access both ends of the inner barrel.  If your replica has adjustable hop-up, turn it completely off (i.e. so that the rubber nub protrudes as little as possible into the barrel).  Make a simple pull-through using a piece of cord or string and a piece of clean, absorbent cloth. Do be careful what you use for a pull-through – many inner barrels are made of very light alloy and it’s frighteningly easy to cut the end of the barrel if you use a hard cord or wire pull-through. Soak the cloth in warm water which has a little washing-up liquid in it and pull through several times.  Finish off by doing the same again with a clean, dry piece of cloth.  That’s it!  Re-adjust the hop-up, re-fit the barrel and you will now have an inner barrel which is free of particles or deposits which are likely to affect the stability of the BB.

Cleaning the barrel from an ASG CZ75

Use top quality BBs and try shooting your replica after cleaning the barrel (and after re-adjusting the hop-up if fitted) and I think you’ll notice a marked improvement.  Groups should be noticeably smaller. Gas flow is critical on any BB shooter and gas flow through the barrel and around the BB is the single place where you can generate the most marked improvement.  Go on, give it a try.  And let me know if it works for you.

Related Posts

Are all steel BBs the same?