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ASG M40a3 Upgrades/Review: My personal build

ASG M40a3

I had my eye on the  ASG M40a3 since they were initially announced, but had always been put of purchasing one due to the lack of information on upgrades and the issues people had been having with feeding etc. It’s worth noting the feeding issues weren’t specific to the ASG M40a3, but rather any guns that has been using the ramp system such as the Tokyo Marui L96 and some of the Well clones etc

However, after a long wait and coming into some spare cash I was lucky enough to pick an ex display model up from Airsoft Sniper Parts UK. I held of ordering any parts at the time as I had some spare bits laying around I wanted to test compatibility wise. Also just to be clear this is the VFC/ASG model, not the cheaper ASG Sportline versions which are entirely different.

Initial Thoughts:

The ASG M40a3 arrived well packaged and come in your standard airsoft style box with a few images and logos etc. Kudos to ASPUK for the good job on packaging and getting it out to my quickly.

Upon opening the box and picking up the rifle I was immediately impressed with the weight of the gun and the finish, it was beautiful to hold and just felt great in my hands.

Cocking the rifle was fairly smooth and I didn’t have any feeding issues with .2s (for chronograph only), the gun was quite loud and seemed to suffer the same echo that you get on other rifles. Not a huge issue as it’s a common thing and with a few DIY mods it can be reduced, but I’ll cover that later in this post.

The ergonomics of the ASG M40a3 in my opinion are quite good, it’s well balanced, the hop up is easily adjustable and has a distinctive click sound when adjusting (this is great for noting down hope levels for different ammo), cheek rest is adjustable etc.

My only small gripe and it’s really small is the hop wheel can easily be turned by accident as it’s close to where you hand would be when shouldering the rifle.

Performance Stock:

As for the performance of the gun, I’ll do this in two parts, the first will be before I upgraded it and the other is after I’ve installed the parts, tweaked ,cleaned, done the DIY mods etc

Putting the ASG M40a3 through the chronograph I was getting around 400fps on .2s and the consistency was around 4-5fps average with a few lows. I put this down to it being a new gun and probably some small air seal issues. But for a stock gun it was good, no better or worse than most stock sniper rifles.

Range on .36’s was actually quite good for a stock gun, they were able to have a decent amount of hop applied and even over hopped. I didn’t have any decent .4’s at the time but I’d have no hesitations stating it could hop .4’s.

Accuracy was again ok for a stock rifle, it wasn’t massively impressive but with a basic clean/polish of the barrel, some PTFE tape around the bucking, DIY barrel spacers  and ensuring it the bucking  was aligned correctly, it certainly did improve and would have been more than adequate at a skirmish.

The barrel in the rifle was a brass 6.03 470mm tightbore, which had the open ended cut, this is good news for people who like running Maple Leaf buckings.

Something about the ASG m40a3 which I think ASG/VFC did a good job on was their bucking and nub combo. Sadly I’ve since used the m in another build which has been sold, but the bucking was very similar to the “Tru Hop” and Maple Leaf buckings in the sense that it has an elongated flat contact surface and makes long gradual contact with the BB which is likely why the gun is able to hop so effectively. The nub they used was essentially a flat nub like the Maple Leaf Omega bucking.

The piston and spring guide are exactly like what you would get in a TM VSR, they are a black poly carbonate and for stock components they would probably last a while.

The cylinder head was brass and of a good quality, nothing really to say about it, it is still in the rifle and working fine. I ordered a second one to do some testing as at the time of building the rifle I couldn’t source a decent aftermarket upgrade. ASPUK I’m looking at you to make me one as part of your new line of “Sniper One” parts 🙂 .

Performance Upgraded:

Upgraded ASG M40a3

I purchased the ASG M40a3 with the intention of upgrading it and using it as my personal rifle, rather than a project to build, test then sell.

Over the years I’ve used various parts from all the big manufacturers such as PDI, Laylax, Airsoft Pro, Action Army etc. In my experience and it is my personal experience, so I’m sure not everyone will agree, the one thing I’ve found is you can get great results from mixing/matching  parts, sure you may have to tinker to get things to mesh, but things such as efficiency, consistency, Joule rating (not creep) can be improved upon quite well.

After the upgrades the rifle has 1-2 FPS variance between shots, great air seal, shooting at 497fps on .2s and 2.38J on .4s.

Is the accuracy good though I hear you ask, for me personally….. yes. If I can see it in my scope and it’s up to 80m and the weather is in my favour, I’m going to be hitting that pretty consistency. At 90m+, if I upped my BB weight, added a Sugru patch or Rhop and did some DIY mods to increase my Joule Creep etc then sure with lobbing and luck I might land a few.

However I didn’t build my rifle to lobs shots and hope luck was on my side, It was built to give me nice accuracy and range at the distances I’ll be realistically engaging people at.

So as it stands today my ASG M40a3 currently has the following parts installed-


You can buy most parts from Empire Airsoft

Maple Leaf 6.02mm 470mm Inner Barrel – This can be purchased here
ASPUK “Sniper One” Spring Guide
Action Army 90 Degree Piston – This can be purchased here
ASPUK Steel Cylinder
Maple Leaf 75 Degree “Decepticon” Bucking – This can be purchased here
Maple Leaf Omega Nub – This can be purchased here
Element M125 Spring  – This can be purchased here
Springer Custom Works “S Trigger” (90 degree zero trigger)- This can be purchased here, I’ll be reviewing this separately in another post.

S-trigger VSR10

ASG M40a3 Upgrade Parts

Some tips for installing some of the parts-

For the S Trigger the sear can sit to high in some receivers causing dragging of the cylinder this seems to happen more on the cheaper clones such as WELL/HFC. It’s very to easy fix, simply add an AEG shim each of the screw to lower the trigger slightly. On other guns the sears sit to low, this can be resolved by sanding the lower receiver where the trigger would sit, this again seems to be more frequent on clones, I put it down the uneven paint and quality control.

Springer Custom Works

For the ASPUK piston, the guide rings can be slightly to wide to fit into some cylinders, this isn’t an issue though and a few minutes evenly sanding the rings is enough to get it to fit. Personally I didn’t find this an issue as such as it was nice to be able to get the rings to have a nice smooth fit in the cylinder based on my set up. Some aftermarket pistons have a considerable gap between the outside of the piston and the cylinder, this can cause slam firing as the sear pushes the piston up and can also add friction leading to a tougher bolt pull.

ASPUK Piston VSR10, ASG M40a3

DIY Mods:

PTFE Tape on Cylinder head threads and dampening pad (removed now, other cylinder head used)
Electrical Tape Barrel Spacers
Foam added to the stock to reduce sound/vibration

ASG M40a3 Stock


Harris Style Bipod – This can be purchased here

Leapers 3-9×40 scope – This can be purchased from here

Paint Job was done by spraying the gun black, then coating in Tan, then a light dusting of brown in stripe, same with OD, then an all over dusting of brown where I’d done OD and vice versa. Then to get the worn look I used this and gentle wiped away the paint in certain areas to different degrees to show the layers underneath.

B&T Suppressor  (modded to actually suppress the sound) – This can be purchased here

ASPUK Suppressor adapter – This can be purchased from here

ASG M40a3 Compatibility:

The ASG M40a3 for the most part is actually VSR compatible with the below parts-

Trigger unit
Inner barrel, you’ll need 470mm
AEG hop nubs
Bolt Handle
Spring Guide
The feeding system is compatible with the TM L96 AWS system.

Final Thoughts on the ASG M40a3:

So my final thoughts on the rifle…It’s a good rifle in stock form, certainly one of the better stock rifles.

Being mostly VSR based it certainly makes a great platform to work on and upgrade with huge potential. With many companies making VSR parts, it’s an easy platform to get started on. It takes an extra few minutes to disassembly due to the hop unit and feed system, but still very easy.

Is it a perfect Airsoft Sniper Rifle? This is airsoft, nothing is perfect 😛 but it is a great platform, it’s different and I think it looks great.

That being said, as with anything there are a few gripes I’d mention. One is that the mags can be a pain to get in and out due to the angle of them, but it’s something you’ll get used to and in no way is it a game changing, more something to be mindful off.

Secondly, the feeding system can be a bit finicky. I’ve been lucky with mine, only needing to slightly sand a few burrs of the feeding ramp , but other ones I’ve worked on have had to have the fin sanded down a smidge.

These are very minor things and every Airsoft Sniper rifle has it’s own issues, for me they were tiny issues and wouldn’t stop me from 100% recommending the rifle to others. Currently this is my favourite build to date!

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