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Discussion Starter · #1 ·
So, after doing research for the past few months, I've finally made some progress on creating my first DMR build!

I've decided to create an SPR, out of my current TopTech M4. The reason behind this, is that it is ideal for a semi only build, as you can trip the AR latch externally via the forward assist. (Lockup issues will no longer be a problem). Unfortunately, this will require a little bit more effort on my part, as there are a few proprietary parts that will need modification.

My current goal for this build is to achieve around 400fps (0.2g) with a max of a 5fps variation. (The reason being that at my local field, DMRs are classified the same as every other AEG, with a limit of 425fps with a .20). For accuracy goals, I hope to achieve consistent groupings at 80ft, using that as a benchmark to longer distances as time goes on.

(Currently, my gun is shooting at 380fps with a 0.2. Checked at a gun tech's after last game of the season, has not had more rounds through since)

To start off this build, I have:
- Disabled the blowback feature
- Replaced the stock gears with standard ratio King Arms steel gears (the machining quality on the stock gears left a bit to be desired)
- Replaced the tappet plate with a King Arms tappet plate (the stock tappet plate was composed of a hard, black, rough plastic that did not slide smoothly, so it had to go!)
- Replaced Aluminum Bearing piston head with a Plastic bearing 'head
- Replaced Single O ring cylinder head with a Dual O ring variety, that is awaiting the Hammar mod for damping+AOE correction
- Reshimmed gears

Without the air nozzle, and the blowback hole plugged, it has a 100% air seal. With the nozzel, however, the lack of an O ring beats my hard earned air seal with a sack of potatoes. So, off to the bin with that!:yup: Which brings me to the list of parts I hope to buy, in which I'd like the opinion of the forum, since you guys know your stuff.

To start things off:

1. Modify Air seal nozzle (M4/M16): Has an O ring, doesn't make the gun breathe harder than a 90 year old man running up three flights of stairs. 'nuff said

2. Modify Accurate Hop Up (M4/M16): Now, originally I had planned to go with a Pro Win, but I had found out that those arent very R/Flat hop friendly. (feel free to correct me on this). I found this lovely little thing, that seems to be a fantastic substitute. It incorporates a gear system in the arm instead of a rounded wheel to provide a better adjustment system.

3. Modify Wellock Bracer: This part is supposed to transfer the vibrations from the gearbox and hop up to the receiver, to reduce the chance of cracking a gearbox. I thought I'd give this part a try, see if it helps!

4. Modify Baton Ryosuku Drop in Flat Hop rubber and nub: I figured I'd buy this to compare with my current G&G Green bucking. If anyone has had experience with this, it would be great to hear!

5. Madbull Stainless 455mm 6.03 Barrel: Since I plan to be pushing heavier weight bbs down the barrel (Type 0 cylinder), I opted to go for the slightly shorter option instead of a 509 to ensure I have the air required to push them out. This barrel will be polished!

6. Shs High torque motor: Other recommendations are welcome!

7. PicoSSR Mosfet: I only need a mosfet to protect my trigger contact, so this tiny 'fet will foot the bill!

Any thoughts/recommendations are appreciated, and I will get photos once all the parts have arrived!
 

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Hey mate!

Sounds like a good start, sounds like a decent list of parts, the Modify parts are great in general, i would skip the wellock bracer, if you're gonna do the Damper-mod you will not need that brace since you're running a low power setup, the damper mod really does take care of the impact enough to render any other solution pointless in sub 550fps setups

dont rely too much on parts to do the job for ya - it's how you put it all together that will set your gun apart from the other 400fps rifles on the field =)

I know it's a bit of a hassle but an R-hop or similar solution DOES improve accuracy when done right.

i like the fact that you're replacing the metal PH with a plastic PH, -you can however add alot of weight to the piston with no worries, it will only help with consistency =)

With the new hopup make sure your tapetplate/nozzle doesn't bottom out in the gearbox-shell when it's at it's furthest stop position against the bucking

I try to get this out to as many as i can, the weak spot in any aeg is the connection between the nozzle and the bucking when the pressure from the piston comes, the bucking expands and if the nozzle does not have that extra travel with constant spring-force towards the bucking to close that gap during the shot, you will have inconsistency, this seems to be a jungle on it's own, some guns comes with perfect mating with lots of travel left for the nozzle without having feeding-issues, and some dont!

just something you should really fiddle around with!

I even milled out the front part of the insides of the gearbox to allow the tappet to travel a bit further, ensuring there's always a spring-force on the bucking =)

Good luck, read the holy grail and think twice cut once and you'll be alright =)
 

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Discussion Starter · #3 ·
Thanks for the info!

An R hop is definitely planned down the road, once I get a feel for what the current setup can do. I'm in the process of tracking down a retailer in Canada that has the Z kit in stock, so I can plan accordingly.

I do plan to invest most of my time and energy into the hop up unit, and am practicing on shimming the arm. One thing I'm caught up on, is should I use the "Floss whip" method, or the "Mega Teflon Tape" mod. I like how the MTT mod eliminates the need for the C clip, as that has been the Achilles heel of my current setup.

That's a good point about the damping characteristics of the silicone, I failed to take that into account when selecting my parts! You, sir, have saved me a solid $35.00. With that saved money, I just might be able to afford stepping up to a Prometheus barrel...

Now, how would you go about Adding weight to the piston? More washers?

The reason I went with a complete set of Modify parts, is to ensure a precise fit between parts, but you have shed light on the tappet plate issue, which I was not aware of! Though, how would milling of the shell compare to sanding the front of the tappet plate?

Haha, I've lost count of how many times I've read the Holy Grail, some might say it's been borderline religious... The people in my small local community need to read it, as 99.9% of them are in the "MOAR TIGHTBORE MOAR BARREL LENGTH" stage in their life!

Cheers, this helps a lot!
 

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If you havn't already bought it. I might advise against a modify hop up chamber for a dmr build. The construction quality is excellent, and also comes with two different style arms, and the gear system has no slippage issues that I'm aware of. It does unfortunately have a few quirks. For one the gear system makes the adjustment more sensitive. This is good and bad because it means that for the same amount of turn as a regular hop up you get more "hop" this means that the entire range of the hop up is only about a half of the turn of the wheel as opposed to nearly the entire turn of the wheel in a traditional hop up. It does however easily allow you to fully engage the hop for heavyweights, but it makes it more difficult to find the "perfect" position.

Hopefully that was clear, it's sorta difficult to explain with words.

Secondly for whatever reason I was getting massive air leaks with my m4. It turned out that the hop up chamber wasn't allowing the air nozzle to reach the bucking to seal (I tested this with several different nozzles and buckings). I ended up having to drill out the back of the hop up chamber slightly which did correct the air seal issues. This combined with the tappet plate mods suggested should solve it though.

Like I said, the quality of the construction is there so if you're willing to deal with the overly sensitive adjustment and possibly some slight modifications it could work for you. I do still use my Modify hop up unit, but in my shorty m4 where I don't care quite as much about precise hop adjustment.
 

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Discussion Starter · #5 ·
You bring very good food for thought to the table!

Unfortunately my retailer just went out of stock of every M4/M16 Hop up unit, instead of the Modify and Pro win, so I guess I'll have to deal with the quirks!

Would you say that it would be worth looking in to a way to adjust the ratio of the gears inside the unit?
 

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I bet something like that'd work, but I don't think they make aftermarket hop up chamber gears...
 

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Discussion Starter · #9 ·
Rifleman, we may have stumbled upon a stroke of marketing genius...

I digress, as long as it stays where it's put, I can deal with sensitivity. Thanks for your insight on this situation!
 

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Discussion Starter · #10 ·
Parts have been ordered, and it is now a race between Airsoft GI and AirsoftParts.ca to see who can arrive first!
 

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Discussion Starter · #12 ·
For sure! I'll do a review of sorts when I document the build, and a comparison with the stock hop up when I can get to the the range when it isn't -27*C... Welcome to Canada, folks!
 

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Discussion Starter · #14 ·
You just made me remember something! I'm also going to test out G&G's new cold weather bucking for a flat hop mod. Supposedly they stay soft up to -40*C! That remains to be seen, however.
 

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to be quite honest, the bucking is the least of my worries when it turns cold, it's how brittle the pot-metal gets and all the grease sticks up in regular guns, i always clean out all the grease in guns i buy or has in for service to WURTH HSS Fluid spray-grease, it does the absolute best job i've ever seen down to -25 degrees up to about 200 c+

(gears can turn pretty damn hot, white lithium turns fluid at about 60 degrees C and just gets thrown around in the gearbox at that point.)

WURTH HSS stays on my gears like fibers at high-speed, it almost looks like it's a belt-system when you look at it in motion cuz it really does NOT wanna leave the gears =)

guarders softest usually works pretty damn good at around -10/-15 As a last way out =)
 

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Discussion Starter · #16 ·
Hmm, I did not know that... It doesn't appear that I can aquire that kind of grease, any alternatives that you know of?
 

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Discussion Starter · #18 ·
So in preparation for parts to finish arriving, I tried my first crack at the Cylinder head damper, and was rewarded with a complete failure. Has anyone got a trick to getting the shape right? Once I try making the inner well, the structure collapses towards the outside edge!
 

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do a little bit of everything at the same time lol, dont just make a dome and then press down in the middle, first you shape the dome, then push down slightly in the middle, reshape the outer corners and repeat that process, use plenty of saliva and dont spin too damn fast =)
 

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I can't give input on all the parts your listing... but I can comment on some...

Modify Flat Hop/Nub.... I actually used one of these in my AUG, worked really well, great air seal, but for my aug the bucking lips stuck out to far into the hop unit and the BB would pinch the bucking as it came up and out of the mag often.

that can easily be solved by a little trimming, other then that it is great, though I do recommend using a namazu hard nub with the little bar, or a prome hard flat hop nub with the bar.

SHS High Torque gears I have not had a problem with, I have used multiple sets, and from what i recall they require a half tooth piston. I do prefer Prome double torque gears.... but they come at a price...

MOSFET..... I have no experience with the one you listed... but I always like to recommend xtremefire mosfets, here is a link to the one I use: Extreme-FIre
 
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