Army R85 DMR project

[cain_126]

I recently bought an army r85 from my friend and I want to upgrade it to a semi auto only dmr/sniper type weapon. I'm thinking of using the following parts:
Guarder sp140 spring
CA25 super torque up gear set
system magnum or guarder infinite torque up motor
SRC 8mm ball bearing set
G&P m4/m16 hop up unit
deepfire 6.02x590mm barrel
deepfire hop up bucking
h-nub
9.6 or 8.4 3300 MaH large battery

I wanted to know if the gear set would work properly with the guns gearbox and if bearings would be fine for a high torque setup. Also I've not be able to find very much info on the deepfire barrels or buckings. But mainly what I need to know is if using a 9.6v battery with the m120 spring that is in my gun will be alright as I've heard the gears spin faster than the piston can travel with a more powerful battery (and also if the 8.4v will have the ability to pull an m140 or m150). Oh and if someone could tell me how to completely disable the full auto function that would be greatly appreciated.

[Booligan]

Unless you plan on boring out the gearbox to handle 8mm ball bearings, the ones you listed won't work. You'll need something sized 6mm, but it already has halfway decent metal bushings stock, so replacing them right away is not terribly important.

[biohazard327]

If you are on a budget i would recommend a matrix magnum. Since you aren't going full auto things should be fine with that spring and those torque gears. Also to disable the blowback take the screw thats all the way in the back upper of the gearbox off and slide the black bolt catch mechanism off.

[cain_126]

Thanks for that info, yeah I am on a tight budget and that's the man reason for the 9.6v question, as I'll probably be buying this piece by piece starting with the barrel/hop up parts. And about the bearings, are you sure they aren't already 8mm? Redwolf's review of the G&G L85a1 said it has 8mm ball bearings stock so I just figured this gun would be the same.

[Booligan]

Yep, I own the gun, and it uses 6mm.
Here's the G&G gearbox, note the big bushings: http://www.airsoftgi.com/product_info.php?products_id=3404
And here's the ARMY, note the smaller bushings: http://store.matrixbb.com/catalog/Gearbox_5867T_lg.jpg

Note that they are oddly shaped, but still 6mm. Mine have been going strong, with the gun as a SAW for a few months now, with no issues whatsoever.

[cain_126]

So would it be necessary to upgrade them to 7 or 8mm bushing to handle the stress of an m140 or m150 or would 6mm be fine?

[utc_pyro]

I've actually built a 600+ fps DMR off of an ARMY l85, so hopefully I can help you out. First off, my gun:

ARMY L85A1



Upper gearbox 1: 542.7 fps w/KSC .25's (Equiliv. to 605fps w/.2's)
"Military Action" Aluminum L85/SR25 piston
Guarder Aluminum piston head W/Bearing
Viton X-ring
Custom Sorbothane pad set
JB Weld re-enforced stock cylinder head
CA M4 blue air nozzle
Systema PSG1 400% spring
"Military Action" V3 spring guide



Upper gearbox 2: 498FPS W/KSC .25's
"Military Action" Aluminum L85/SR25 piston
Guarder plastic piston head W/Bearing
Custom Sorbothane pad set
Stock cylinder head
Stock air nozzle
Guarder SP160 spring spring
Element V3 spring guide

Lower gearbox:
Stock gears, stock shimming (checked and it was OK as is)
JG High Torque motor

Barrel system:
King arms hopup chamber
Firefly bucking
DBC 6.01mm x 509mm barrel

Electrical:
Prototype SW-Panther
Mystery 2650mah 11.1v 20C lipo
14AWG wire throughout

External:
G&P long mock mock mock mock mock silencer
G&P 3.5x ACOG

First off, it's a 6mm gearbox in the L85, and it's design is such that it will not take to boring out very easily. Just leave the stock 6mm metal bushings, they'll be just fine.

Dont bother with the upgraded gears, they'll just cause headaches. Leave the stock ones.

On the motor, I'd advise staying glear of the Systema or for that mater the Matrix "Magnum". Poor quality on both, the G&P M160 is a much better motor in that performance range and cost ~$20 less then the systema. Ether way though, those are overkill for waht you are wanting to do. Just get a SRC high torque, JG High Torque, or Guarder Infinate torque up motor for it.

Also, I'd suggest taking the battery all the way up to a lipo. It's nor verry expensive and oferes huge performance advantages. Here is the one I use: http://www.dealextreme.com/details.dx/sku.18109

You'll want to upgrade the piston on it. The stock one WILL NOT last very long. I'd suggest puttin one of these in: http://www.airsoftpark.com/military-action-full-teeth-aluminum-piston-r85blue-p-770.html

Also if you want to extend the barrel you'll need a SR-25 or PSG-1 cylinder. This one is cheap and will get the job done: http://www.airsoftpark.com/military-action-sr25-stainless-steel-cylinder-p-1159.html

Finally on disabling full auto: You should be able to just monkey with the cam system on the selector to force it into only one position. Another option is to drill a hole below the selector and put a screw into it. This will prevent you from being able to put it into full auto on the field, but you can unscrew it if you ever need to.

[cain_126]

Thanks a lot for your help. I just have a couple questions left. First off I have a G&P sr25 piston right now, will that be fine for a 450-500fps setup? And about the battery, will a 4.2v lipo really be better than a big 8.4v?

[utc_pyro]

That lipo is a 11.1v, it's just labeled wrong on the website. The G&P piston will be fine for a while, but I ripped one in half (literally) in my gun using an SP150 after about 2000 rounds. That's when I found those AL ones just put those in both of my uppers.

[cain_126]

Thanks for clearing that up for me. Now I only have 2 more questions. Why do I need the longer cylinder to increase barrel length and is it worth it? And if I buy an 11.1 lipo right now with an m120 in my gun will it destroy my piston?

[Wetsuitxninja]

You wont be able to change cylinder length because the limiting factor is the cutout for the sector gear.

On mine I used some fiber washers and used a standard length piston, (G&G SNC Piston) and a standard sector gear.  The issue I had with the longer piston was the pre-engagement with a higher ROF.  (Lipo and M130 I had this issue so you probably will too)

Im chrono'd at 440-450 with .20s and hitting 27 bps, and around 10k rounds through the gun as it sits.     

Swapped out the Bevel as well. (used KWA gears)  Ive got a v7 G&P spur for when\if the stock one goes.  I like where you are going with it, should be sweet. 

[cain_126]

So if I can't switch to a longer cylinder is it impossible to use a longer barrel?(would going from 509mm to 590mm really make a noticeable difference?) And do you think a lipo would be fine once I get an m140 or above in there? or should I just stick to big 8.4 and 9.6 NiMh batteries? Also can anyone tell me if a prometheus tightbore would be better than a deepfire 6.02 accuracy wise?

[wtfasiankid8o8]

I can tell you the prometheus will beat it, and you'll probably be prone less jams than with a super-tight barrel like a 6.02, although you are only going semi so the choice remains open.  I would still get the prommy.

Also, I've seen guns running on lipos and m140-150's and crash, but for the sake of just DMR'ing, I suppose there will be no harm done.

As for the cylinder issue, you can use a standard non-ported cylinder, because that would probably be your best bet to getting as close to an SR25/PSG cylinder as possible.

[cain_126]

So with the standard length cylinder I have I could use a 550mm prometheus or 590mm deepfire barrel without a loss of compression? And would I experience the same problems with timing using a 7.4 900 mah battery? The battery thing is important because it will be the first thing I replace and I can either have my friend make me a custom 8.4 or 9.6v 3300 mah battery or I can by the 7.4 lipoly for the same price. keep in mind that I will be using full auto and everything (well more like 3-5 shot bursts) until I can get enough money for all the cylinder parts and the barrel especially if I decide to spring for the prommy.

[Lemon lime]

I would recommend a different Hopup unit. G&P's are not the greatest ones. Maybe a KA unit.
I suppose you know you will have to cut the bottom leg part down for it to fit.

[cain_126]

Are those element polycarb hop up units any good? Or should I stick with systema/KA units?

[Lemon lime]

Are those element polycarb hop up units any good? Or should I stick with systema/KA units?

I don't know. I would go with the KA over Systema.

[Wetsuitxninja]

Are those element polycarb hop up units any good? Or should I stick with systema/KA units?

I actually love my element. Ive got that in my R85, as well as my M16.  For a fact I gained on average 8 fps vs the stock G&G hop up unit.

[cain_126]

Can someone explain to me exactly what a bore up cylinder does and why I would need one to extend my barrel to a 550mm length? Also would 40mm of extra barrel length make a notable difference in my effective range?

[phoenix212]

Can someone explain to me exactly what a bore up cylinder does and why I would need one to extend my barrel to a 550mm length? Also would 40mm of extra barrel length make a notable difference in my effective range?

Bore up cylinder adds more area to the cylinder so it can (provided compression is good) push more air through the barrel, once you get to a length that is above your cylinders output the bb wont have air pushing it for the entire travel through the barrel thus lowering your fps. The difference between 509 and 550 will be minimal at best, a few millimeters difference at 100 feet would be an abnormal at best.

[cain_126]

Alright so I just have one more compatability question. Will a psg-1 piston and cylinder work together in the r85 GB? And what is the difference between psg-1 springs and normal springs?

[phoenix212]

I am not sure whether it will work, but I know psg-1 springs are longer

[cain_126]

Alright so this setup should work right?
Military action aluminum R85 piston
Element V3 spring guide
Guarder sp150 spring
Guarder infinite torque up motor
Madbull 6.03x509mm barrel
Madbull shark hop up bucking
Element polycarb m4/m16 hop up unit

And I'm trying to decide between using tsd .28 or ksc.3g bbs.

[Wetsuitxninja]

KSC .30s for sure.