DMR build

[Sheepy]

Hey guys just ordered a bunch of parts that from what I’ve researched there all pretty decent for a dmr build. But I wanted to get your guys thoughts and any tips you might have for me when assembling them to ya know increase, accuracy, compression or decrease stress on the shell or parts 

shs high torque motor

ares efcs 

super shooter 16:1 gears 

shs 14 tooth aluminium piston

guarder 

action army cylinder head 

action army piston head

element m4 nozzle

element reinforced rotary spring guide

element tapper plate 

m130 spring

ultimate cylinder for 401 to 450 barrel length

any help would be appreciated guys

[Wo1f]

I'd exchange the piston for an ASG ultimate blue piston. i usually try and keep the cylinder head and the nozzle to the same brand to avoid tolerance issues but you should be okay. What fps are you going for? And most important of all, what are you doing in terms of hop up as thats the most important part of a dmr.

[Lozart]

Obligatory posting of the best thread about building a DMR ever http://www.airsoftsniperforum.com/43-longrange-aegs/892-holy-grail-building-your-dmr-aeg.html

[Sheepy]

37 minutes ago, Lozart said:

Obligatory posting of the best thread about building a DMR ever http://www.airsoftsniperforum.com/43-longrange-aegs/892-holy-grail-building-your-dmr-aeg.html

Cheers man but I’ve read that cover to cover about ten times it’s a good read 

[Lozart]

2 minutes ago, Sheepy said:

Cheers man but I’ve read that cover to cover about ten times it’s a good read 

 

Certainly is, shame the pictures don't work any more though.

[Sheepy]

1 hour ago, Wo1f said:

I'd exchange the piston for an ASG ultimate blue piston. i usually try and keep the cylinder head and the nozzle to the same brand to avoid tolerance issues but you should be okay. What fps are you going for? And most important of all, what are you doing in terms of hop up as thats the most important part of a dmr.

I was going to get the asg one but from what I’ve been told the shs one is absolute tank. And hop up ive got a ultimate hopup chamber with a maple leaf bucking and I’m going to 440 +\-1 hopefully

Just now, Lozart said:

 

Certainly is, shame the pictures don't work any more though.

Ye man the pictures would of been so useful 

[Wo1f]

The asg blue (or red if you really need it) is really tough. I don’t like the idea of an aluminium piston rubbing on a zinc gearbox shell. 

 

Good choice on the bucking. I’ve had great luck with maple leaf. Just make sure you use the omega nub with it. 

[Iceni]

I'd go with the cheap shs bore up kit.

NOT for the volume increase. But for the compression increase when using a 2.5mm x 20mm o-ring. The stock 2.5mm x 19mm o-ring that comes with those kits isn't up to much with the slight diameter increase but the 1mm larger ring is quite a bit tighter, too tight for a standard cylinder but in the bore up it'll start to compress almost instantly and have a stunning airseal inside the bore.

Get the correct kit for the gun however as the airseal nozzle is a larger bore with the bore up kits. The one supplied will also have a double o-ring seal.

The kit at £24 replaces 4 or the components you have selected (Cylinder, Cylinder head, Piston head, Airseal nozzle), so it might actually work out been cheaper as well.

 

https://gun-fire.co.uk/product-eng-1152212768-Bore-Up-Set-for-M4-Replicas.html
 

Just remember that you will need a 2.5mm x 20mm nitrile o-ring as well. You can get 50 rings for £6 from here. The 20mm is inside dimension.

https://simplybearings.co.uk/shop/Seals-O-Ring-Seals-NITRILE-O-Rings/c19_4501_4705/index.html

The rest of the stuff you can get from AK2M4. He has in stock

SHS rebranded 16:1 gears, not as good as the super shooter but not bad either and half the price. Stock 18:1 would also be fine.
SHS rebranded 14.5 tooth piston CNC. Stock would also be fine.
SHS rebranded stainless v2 spring guide with bearing
SHS rebranded M130 spring (425fps) You will need to fettle this a little.

https://www.ak2m4.co.uk/index.php?route=common/home

You don't need to go crazy with gear in the box. You are only bringing the gun back up to 400fps, and that is stock for the USA market, so pretty much all internal parts can cope with those stresses. It's USA crazy builds where 500fps is legal where the majority of the mods are needed.


 

 

[Sheepy]

41 minutes ago, Iceni said:

I'd go with the cheap shs bore up kit.

NOT for the volume increase. But for the compression increase when using a 2.5mm x 20mm o-ring. The stock 2.5mm x 19mm o-ring that comes with those kits isn't up to much with the slight diameter increase but the 1mm larger ring is quite a bit tighter, too tight for a standard cylinder but in the bore up it'll start to compress almost instantly and have a stunning airseal inside the bore.

Get the correct kit for the gun however as the airseal nozzle is a larger bore with the bore up kits. The one supplied will also have a double o-ring seal.

The kit at £24 replaces 4 or the components you have selected (Cylinder, Cylinder head, Piston head, Airseal nozzle), so it might actually work out been cheaper as well.

 

https://gun-fire.co.uk/product-eng-1152212768-Bore-Up-Set-for-M4-Replicas.html
 

Just remember that you will need a 2.5mm x 20mm nitrile o-ring as well. You can get 50 rings for £6 from here. The 20mm is inside dimension.

https://simplybearings.co.uk/shop/Seals-O-Ring-Seals-NITRILE-O-Rings/c19_4501_4705/index.html

The rest of the stuff you can get from AK2M4. He has in stock

SHS rebranded 16:1 gears, not as good as the super shooter but not bad either and half the price. Stock 18:1 would also be fine.
SHS rebranded 14.5 tooth piston CNC. Stock would also be fine.
SHS rebranded stainless v2 spring guide with bearing
SHS rebranded M130 spring (425fps) You will need to fettle this a little.

https://www.ak2m4.co.uk/index.php?route=common/home

You don't need to go crazy with gear in the box. You are only bringing the gun back up to 400fps, and that is stock for the USA market, so pretty much all internal parts can cope with those stresses. It's USA crazy builds where 500fps is legal where the majority of the mods are needed.


 

 

Ye I was going to get the bore up kit but the few people that I’ve talked to about them have said they’re not much cop and are less durable than a standard but they could be talking out their arse. The stuff piston head and cylinder are a really tight fit so they should be good and ak2m4? I’ve never heard of that shop I’ll have to have a look all of my usual part shops have virtually nothing in stock

2 hours ago, Wo1f said:

The asg blue (or red if you really need it) is really tough. I don’t like the idea of an aluminium piston rubbing on a zinc gearbox shell. 

 

Good choice on the bucking. I’ve had great luck with maple leaf. Just make sure you use the omega nub with it. 

Ye a few of the guys on reddit said the same but my shell got a solid black coating over it so I thought it was one of the reinforced ones that it shouldn’t cause a problem with

[Iceni]

AK2M4 stuff is fine, He regularly posts on here and has a good reputation from the community. So if you did have problems he would resolve it quickly.

@ak2m4

I'll let him tell you about his products. But for the price he's well on point.

He's also one of the guys that can probably advise you best on internals since he has a shop full of them and all the feedback that goes with that.

The bore up kits without the oring upgrade are pretty lacking. They need the o-ring to get the best seal and most people don't bother or don't know it can be upgraded. They don't offer much more volume and in that regard they don't do what they should, but for getting a great seal I have yet to find a better combination. The cylinders are thin walled and not as solid as the stock ones, but they will function without any problems provided you don't damage them.

You will need a decent lube for the piston seal. And it'll feel much stiffer on the push but that will bed in. If you use a stock 19mm ring you will find no matter how fast you push it'll struggle to make a seal.

 

[Sheepy]

1 minute ago, Iceni said:

AK2M4 stuff is fine, He regularly posts on here and has a good reputation from the community. So if you did have problems he would resolve it quickly.

@ak2m4

I'll let him tell you about his products. But for the price he's well on point.

He's also one of the guys that can probably advise you best on internals since he has a shop full of them and all the feedback that goes with that.

The bore up kits without the oring upgrade are pretty lacking. They need the o-ring to get the best seal and most people don't bother or don't know it can be upgraded. They don't offer much more volume and in that regard they don't do what they should, but for getting a great seal I have yet to find a better combination. The cylinders are thin walled and not as solid as the stock ones, but they will function without any problems provided you don't damage them.

You will need a decent lube for the piston seal. And it'll feel much stiffer on the push but that will bed in. If you use a stock 19mm ring you will find no matter how fast you push it'll struggle to make a seal.

 

Ahh well in future I’ll probably get most of it off him then :’) ye I know picked a maintenance kit the other day that’s got all the lubes  and greases a guy could want and ye I’ve heard the cylinder are prone to get deformed from a little bit of damage because of a loss in structure,

im looking at doing a Mid to long range support weapon build in the future so I’ll probably end up putting a bore up kit in that but with a ported cylinder to prevent feed back. Similar to a l86 lsw build with a long barrel

Also would you say it’s worth just getting a 20mm o ring anyway for a better deal?

[Sitting Duck]

A lot of compression is also done to the piston head itself....

 

Some piston heads are just moderate crap no matter what size/thickness/material o-ring you use

ATM I've fallen in love with stock JG piston heads

often they have a double o-ring stock plastic cylinder head too (result)

 

But the piston head (rest of piston is junk with heavy alloy spacer/mount)

The piston head - just works, seals immediate and when a nice polished cylinder used

provides great solid compression, not slowly moving air escaping but rock solid stuff

very little drag or pop when yanking out of full cylinder meaning it is working as it should

 

Type of stuff you dream of than settle for good or very good compression at best

Even some new decent heads have been slightly good at best

A few have been f*cking dire no matter what o-ring/cylinder combo is tried

So I think a fair bit is down to the piston head to begin with imho

 

Well enough waffle....

 

 

If anybody has one of these in their junk/spares box

widen the holes very slightly maybe (no need to go nutz)

slap it in piston (m3 bolt, nylon locking nut washer or whatever)

test it out with a few o-rings you have around and you should be quite pleased

(if you don't get very good/great compression you forgot the o-ring)

 

Obviously polished cylinder and o-ring & ptfe if needed on cylinder head etc....

(test cylinder head leak in a basin/bowl of water like checking for puncture)

 

But think quite a bit of the difference between good & GREAT compression seal

Well a good portion of it is down to the piston head itself too imho

Well so I have found - got a number of crap/meeeehhhhhhhh piston heads

(plus never got really good seal with a std G&G piston head)

[Iceni]

20mm rings are too big for a stock cylinder, you can get them in but the resistance is far too high.

I have 19mm ones for my stock cylinders, They work well but are the same as your regular stock ones. There are some 19.5mm ones but I haven't picked any of those up as I was that impressed with the bore up kit on 20mm ones that I have been converting my guns to that setup. Not had any problems with the cylinders yet but that doesn't mean it won't happen in the future.


Again with what @Sitting Duck has posted, the piston head itself needs to be right. The SHS bore up ones are well finished aluminium, and have a CNC smooth rear face, It's the rear face that needs to be right,  It needs to be strong enough to hold the pressure without bending and deforming, and smooth enough that the o-ring gets a solid seal on it. It also needs to be as close to the cylinder wall as is possible. If those are right then the O-ring will seal like a trooper, If it's wrong it doesn't matter what you do to the rings it'll always be poor.


It's the rear face that is actually your compression wall, not the front of the piston. The front is a stopper.
 

[Sitting Duck]

7 minutes ago, Iceni said:

 

... It's the rear face that needs to be right,  It needs to be strong enough to hold the pressure without bending and deforming, and smooth enough that the o-ring gets a solid seal on it. It also needs to be as close to the cylinder wall as is possible. If those are right then the O-ring will seal like a trooper, If it's wrong it doesn't matter what you do to the rings it'll always be poor.
 

 

200% agree with ya sir, that was my conclusion too I have found

certain ports can assist with blow/swelling the o-ring to seal

but all/most means jack if it isn't supported at back perfectly sealing the mofo

some really cheap/crap stock heads come in two parts and can mix stuff at a push

but really - too much f*cking about if you can find a very good or great one at times

 

Often we have to settle for good or rather very good depending on what we have to hand

But if/when you get the combo and get a GREAT seal - omg you really notice it

Wish I could find a place that sells the JG head on its own, I'm that impressed with it

[Arwen]

5 hours ago, Lozart said:

Obligatory posting of the best thread about building a DMR ever http://www.airsoftsniperforum.com/43-longrange-aegs/892-holy-grail-building-your-dmr-aeg.html

Thanks for this, first time I've seen it. As I am aiming to make my Recce a 350fps "DMR" this may prove rather useful!

[ak2m4]

That JG cylinder and piston head look very similar to the CYMA ones, same colour plastic as well.  Does it have the unusual piston head fixing plate / screw?

[Iceni]

This is some food for thought @Sitting Duck

I just took apart another aps AUG I picked up for the son. It's got a different component set to the ones that came stock in my model.

I grabbed an image of Evike to see if what I saw was a manufacturing feature, and sure enough it is.

Have a look at the sealing edge of the piston head. You see that deformed flat spot... It's the injection point for the plastic. Absolute junk.

I'm actually at a loss as to how that passed any form of QC from the design team.

[Sitting Duck]

@Iceni Wow - what a w@nky bit of QC

 

 

19 hours ago, ak2m4 said:

That JG cylinder and piston head look very similar to the CYMA ones, same colour plastic as well.  Does it have the unusual piston head fixing plate / screw?

 

 

The Cyma piston head is a concave type head with 8 holes near the rim

(not a bad head but stock o-ring is often meeeehhhhhhhh and needs changing but not bad at all)

Really not a bad head - worth keeping in cheapo cyma upgrades

 

JG one is a five hole flowery or pentagon set more in middle of radius but totally flat

but even stock as is, it just seals very very well

 

look here at piston say 5:00 onwards....

 

 

 

compression test at about 6:25 - it works very very well like I said

 

Most China guns have that f*cking alloy spacer bollox inside piston - often spring is hooked into it

So need to unscrew/unhook and dremmel off hooky bit, then use m3 bolt washer nylon locking nut etc....

Cyma, JG, SRC - even ICS Sportsline have that f*cking alloy bollox spacer usually self tapping screw crap

(but ICS the spring isn't hooked into spacer like most)

 

I'm thinking of doing a modest DSG G36c using mostly stock parts for cheap budget as stock stuff looks good

(metal rack piston of course, JG gears seem both sturdy and run smooth on a steel 7mm bushing box)

So trim up tappet fin, swiss metal rack piston and reassemble, beefy spring SHS DSG and that is about it

Motor - could be an oem JG 22tpa but likely on ferrite, could reshell that arm into old neodym can

Or might be OK pulling m140/150 with a beefy lipo (just), but think that is pushing it tbh on ferrite magnets

Hence me saying about the damn good JG piston head & also the 2 x o-ring cylinder head will do very nicely too

The 250mm barrel & a spare cylinder with a port that piston just clears means max volume & filling OK (I hope)

So should get max possible fps/joules for a DSG build so a m140/150 might get 275+ fps 25-30rps neodym can (7.4v)

Or 40-45rps just over on 11.1v (maybe a little more fps as seals are damn good but a snappy project for little work)

Well - just a project idea I'm thinking of doing due to barrel length and great seals etc....

Could make a nice SS SSG build on say a zci 300mm barrel too with 13:1 but DSG one looks likely as I said

 

All I know the stock piston head rocks, I don't rave about stuff unless I'm really really impressed by it