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Classic M4 Build Off—Leo’s Edition

2727 Views 64 Replies 6 Participants Last post by  rue_exe
Alright y’all! After some harmless confusion, I have figured it out. Everything related to my build will be posted here.

I’ll be competing against @danerd but I’ll be taking my build in a completely different direction.

My base gun is a TM M4A1 carbine length AEG (not the NGRS), chosen to provide a bit of a different, more classic flavor compared to what I usually run, as well as having a few desirable attributes for the build.

For now, my concept is of an “apocalypse” AR, built using a combination of old parts and new.

Everything will be “weathered”, and most likely painted (patterns and colors TBD).

I’ll be keeping the carrying handle, as I think it looks kinda sick.

I’ve decided to keep the original stock to help ground the build, although I’ll probably be adding a stock pouch.

I’ll be changing the grip, mostly likely to an EMG/Strike slim grip, but that’s yet to be determined for sure.

For the optic, I’m caught between form and function: function would have me do either an open reflex sight, or none at all, but I have a 1-9x hunting scope that would look great, and really fit the theme.

I’m still debating the muzzle device I want to use. For regular use, I have a very nice looking RS Surefire Warcomp .556, or a foam filled “mock” suppressor can that may be used to hide an extended barrel, but I also have an RS Silencerco suppressor for a real M4A1. It can’t stay on the build permanently, but it can stay for a couple of pics.

I’m looking at adding a sling, but not sure yet—I have a buddy who somehow acquires just about every piece of tactical gear known to man, so I’ll see if he’s got anything.

For the hand guard I’m still doing my research—the Magpul MOE SL is my top contender, but I’m also admiring the BCM PMCR. Nothing determined yet—research to be done!

I’m looking at adding a Krytac Trident sling plate, but first I have to see about sourcing a sling.

That about wraps it up for my ideas on the externals, now we get to the insides:

Danerd is probably going to outdo me on the externals, build aesthetics, and cool factor (GBBR), so my chance to pull ahead is on the inside. I’ll be using a GATE Pulsar, with the aim to achieve an effective range of 90 meters using heavy ammunition. I’ll be trying to keep the FPS under 450 w/ .20g, but if necessary I’ll go up to 500.

Since very few people have this engine so far, the limits aren’t well known, so I might have to adjust my effective range goal as I begin tuning and tinkering.

For now, I’m trying to use the supplies I have on hand, and unfortunately I only have a couple inner barrels in the 380 range, which is where I’d ideally want it.

I have two Lambda SMART barrels, 6.08mm and 6.03mm, but both are 509mm. The HPA engine should be able to correctly volume either, but it may cut down on efficiency and potentially even accuracy.

Unless I source a different barrel, the most promising choice is looking to be a T.N.T. S+ 387mm.

I’m going to take a look at the stock hop unit, but since I prefer to work on rotary units, I’ll likely use a G&G polymer rotary (assuming it fits).

I’ll be testing several packings and nub combos to determine what works the best with the engine and with the gun itself, but I’m leaning towards a ML MR.Hop silicone 85* and either a 3D printed RHop arm or a homemade concave nub (I would probably cut out of plastic; broken barrel clips work great, since they’re already the right ID.)

Everything will be exhaustively tested, fitted, and stabilized to attempt and provide peak accuracy.

Unfortunately, Danerd’s build looks to be no slouch either, so I have my work cut out for me.

The second requirement of the internals, is that I’m going for complete silence. Though accuracy comes first, I will certainly adjust barrel length and other factors to attempt and make this rifle as quiet as possible. (Here’s where the foam-filled suppressor comes in)

And that about wraps it up for my build ideas/notes so far.

And one final note; Since I didn’t want to allocate my budget to buy a $200 Yong Heng air compressor, I opted for a hand pump to fill my air tank. Put your bets in, ladies and gentlemen; how many times do I fill the tank before I give in and buy a real compressor??
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Okay y'all, the Pulsar has landed. After some mighty shenanigans, it works!

Here's my thoughts and experience on the build so far

My regulator seems to be stuck on 140 PSI (until I can mess with adjusting it), so that's what I tested on. Since I know nothing about HPA tuning, I invite all you with experience to criticize my methods...

First off, adjusting the Pulsar settings is a breeze. You can even tune as you fire, thanks to GCS allowing you to switch into shooting mode at the touch of a button. This thing also has a lot of tuning range... It allows you to turn the RPS up to 100, though I'm unsure if the system will work that fast.

On first test, using Madbull .38g (heaviest I have around. BLS .40g is on the way) and a Lambda 6.08mm x 509mm, I only chronoed at 1.2J, which seemed pretty low to me. This made me think my FCU settings were improper, and I starting messing with things. First I tried tuning the "main valve time" setting, which seems to regulate just how much air the Pulsar outputs. Let me tell y'all… this thing can produce a TON of volume. Moving the "main valve time" up to 6ms from 5ms fixed my voluming issue, and the rifle now fires at a healthy 2.25J. But, of course, I wanted to go farther, and kept increasing. My barrel noise kept getting louder, and the joules rose up to 3J at 10ms main valve time. Any farther any I'll need a longer barrel to keep the joule output the same. I'm sure this is horribly inefficient anyways, but I kinda want a 650mm barrel just to see what this thing can do. I turned it back down to 6ms, which seemed to produce the best barrel noise without losing joules to undervoluming.

The next setting is labeled main valve pause, which I equated to nozzle dwell, which according to my limited understanding is how long the nozzle stays extended. Increasing the nozzle dwell drastically increased my consistency, from ~15 FPS to ~4 FPS. I'd like it to be even better, but for now increasing the dwell from 10ms to 12ms is enough to make me happy.

Up next are the "boost timer" and "main valve boost time" settings, which I have no clue about, and haven't messed with.

With adjusted settings, I'm sitting at 2.25J, ~4 FPS, and the firing noise is like a quiet snap. I have yet to test, but I'm assuming that it'll be inaudible past a few yards. Unfortunately I was unable to test accuracy, since my stupid Umbrella Armory RHop arm broke. But, I'm still happy with what I'm getting out of this thing so far!
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Is there supposed to be a pick? I’m curious about this engine….
Is there supposed to be a pick? I’m curious about this engine….
What do you mean by a pick?
sorry, auto correct….pictures?
Unfortunately, my wifi hates this forum with a vengeance, so I can't upload photos for the time being... :(
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Oh well… I can be patient….hope the Wi-Fi starts to behave….
my wifif hates this forum. For any and all picture requests, PM me your email and I'm happy to send you pics of whatever

Alright y'all--I modded my G&G stock hop arm and the build is once again fully functional! Er, aside from not having a grip and the air line not being the right length and other shenanigans like that. But it does shoot, so that's a plus.

Also, now that I can actually adjust the hop unit, this thing is dang accurate. No full range numbers or groupings sizes just yet, but I was sending .38g past where my eyes could easily track, so that's a good sign in my book. The next question before I start fine-tuning the Pulsar settings is whether I'm switching barrels or not. The Pulsar can easily volume my 509mm x 6.08mm... but do I really need to? Or want to? I have a 430mm x 6.05mm that should, on paper, shoot just as well without having to deal with 80mm more of barrel length. Both in terms of practical length, and in terms of efficiency. Shorter, tighter barrel = higher air efficiency.

Ah, choices. I have some testing to do, but thankfully it shouldn't be too hard--the GCS app makes adjusting volume settings, etc, a breeze. So much easier than when you want to change your setup or your BB weight with an AEG!

On a side note, on auto I have it cycling at 77 RPS so far. This is without any real tuning (and without testing if it'll actually feed that fast), but interesting to note that speed this thing allows you to set.
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Just purchased some ASG .48g. Time to start really pushing my range with this thing! I got some advice on tuning the Pulsar, and so I should be able to set it to any weight I want within minutes.

On a side note, the Pulsar seems to have some interesting extra settings that aren't typically found on this kind of engine. As I can find zero info online, I'll be updating what I learn as I experiment.
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You may have passed the wall with .48g.

Staying within rates for field use with such a heavy bb is like shooting frisbees, really slow frisbees. It's going to be like ~200fps
You may have passed the wall with .48g.

Staying within rates for field use with such a heavy bb is like shooting frisbees, really slow frisbees. It's going to be like ~200fps
So, my ASG airsoft calculator says .48g @ 2.25J should come out to 320 FPS. This should put me right under my field's sniper limit of 500 FPS w/ .20g... of course I'll be testing all of this.

Also, chances are that I put this thing together, tune it all up, do range and grouping test, bring it to a few games, and then use the Pulsar in a different build or change the settings to CQB. As much as I love the long shot, I'll play less with a DMR than with a carbine build, so I won't always be shooting .48gs out of this thing.
I do the same with my AR based HPAs. I‘ve got a short barreled upper for my SR25 that allows me to use a 363mm inner barrel, if I wanna run something smaller.
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Surprisingly, the upper from a Classic Army Nemesis PDW I have is the closest to fitting. If all else fails I can probably file down a few edges, and strap the TM outer barrel and accessories on. (Assuming anything fits correctly)

Before I do that, I'm going to try the trick Guges mentioned about putting metal rods inside the upper. I also had the idea that coating the insides in epoxy might increase the stiffness, but I'm not sure about that yet.
Alright. I've pretty much given up on the stock receiver set... Now I'm on the warpath trying to find a set that's TM compatible and has colt markings. It seems I'm looking at old G&P, and maybe E&C, which seems to be the more affordable and common option. If anyone has a marked E&C receiver or knows where to source one I'm all ears!
Hong Kong...wgc...look for one that is blurred out.
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Okay, the Internets have been searched... WGC has a couple receiver options, but they're both M16 receivers, rather than the hard to find M4A1. I did spot one store located in Greece that had a proper M4A1 receiver in DE, but I decided I wasn't going to order from Greece.

I'm on a short vacation right now, so I'm away from the workbench, but as soon as I'm "back in the office" I'll be testing the various receivers I have for compatibility with the TM gearbox, and trying a few different ideas to stiffen the stock TM upper. If those fail, I'll be back to considering the E&C M16 receiver. While I would prefer to keep it an as M4A1, I feel like an M16 receiver doesn't compromise the "classic" feel (aside from not being 20") too much.

Who knows though, Danerd might attempt to murder me if I stick all my collected parts on an M16 receiver...
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Who knows though, Danerd might attempt to murder me if I stick all my collected parts on an M16 receiver...
I will allow this
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Chrono readings @ 140 PSI with .38g once I tuned it down a little bit. Could be more consistent...

...and, of course, my other pictures once again refuse to load. :mad:

Y'all will get to see my messy testing station later.


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Lines, wires and clutter glaore... I love it, and the other part of me is having a bit of a coniption about it being messy... I just tell myself that "Organized Chaos" is fine.
Hey, it did attach! Kinda.

Hopefully some of the mess will disappear as I get the build fleshed out with a pouch to hold the tank, and probably a smaller battery--I'm using an AEG 7.4v right now.

And my yogurt, 'cause who wants to test on an empty stomach? :D
Alrighty. A package from Guges just came in, and I had good laugh over the captions on some of these ancient deep fire parts. I kid you not, the bushings literally say "ENDOW YOU WITH A VIOLENT WARRIOR" on the front in all caps...

Some of these parts are clearly just for fun, like the ancient pistons, but others will probably see actual use, resurrected in new builds and upgrades for friends. No one put an expiration date on cylinders and barrels!

I also have a TMish compatible Classic Army receiver set in. I'll be keeping the TM lower, with those original unlicensed trades, and substituting the CA upper, and potentially a CA outer barrel set that Guges also sent me, though the TM one isn't that bad anyways...

I'm also going to immediately use that DF spring guide in the HPA build, as the TM one only has a nut in it instead of being threaded, and really needs a spring to keep it in place...

I may just have a finished build together soon!

...Though I still need to figure out how I want to HPA mod my grip, and also how to resize that grip line...
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