Airsoft Sniper Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
37 Posts
Discussion Starter · #1 ·
Hey, I was hoping to build a silent and accurate m4-based DMR. The silent part is coming along nicely, but the accuracy is really depressing.

The platform is a Dboys SPR Mk12 Mod0, with:
-king arms gearbox (this one)
-ab mosfet
-systema m130 spring (shoots 128m/s without variation)
-prometheus neo strike hop-up chamber

..and a combination of the following parts:
-prometheus 420mm 6.03 barrel
-madbull python 509mm 6.03 barrel
-prometheus soft rubber
-guarder hard rubber
-madbull soft rubber
-prometheus nub
-madbull shark nub
-airsoftpro snob (this one)
-G&G 0.25 bbs

I used almost every combination of the spare parts I have. I followed most of Vindi's dmr guide, tweaking my hop-up, yet my accuracy sucks. I hit around 2-5/10 torso at 70m. I even tried gluing the h-nub to the hop-up arm and filing down the rubber's bump, which seemed very logical, but yielded the worst accuracy. My stock G&P Sentry is far more accurate, and that is a cqb version.

My goal is 10/10 torso shots at 70m, with a maximum velocity of 140m/s. What could I be doing wrong?1 I have no velocity variations on the chrono, so it's not an air-seal related problem. Could it be the bbs?2 After I install a stronger spring to get me closer to 140, I'm thinking about switching to KSC 0.3 super grade, or bioval 0.30, which should I go with?3
 

·
Registered
Joined
·
807 Posts
I use Bioval 0.3s in my DMR and my M9 now. No problems what-so-ever, there was even no improvement after I cleaned them, so I don't anymore.

What do you mean by "tweaked" the hop up. If you haven't done the shims I would HIGHLY reccomend doing that one.

If you truly have ZERO variance in your FPS, then it has to be an issue from the hop up forward with the exception that it may have to do with the nozzle as well. Counter sink your nozzle for consistant BB placement. Teflon and dental floss your barrel and bucking if you haven't already and chose one of those barrels and polish the c$#p out of it and finish it off with a thin wax (obviously you can't polish the madbull because of the teflon).

Also, choose one bucking and stick with it. I have had great success with Guarder Hard buckings, so thats what I would go with, but thats up to you. Make sure the bucking is clean on the inside before you instal it. If it is one you have pulled off of an old gun there can be Mould release all over the inside of it from unwashed BBs, this will adversely effect your hop, and if you dont have the nub connected to the arm then it will become an unpredictable effect.
 

·
Registered
Joined
·
1,045 Posts
As has already been said, you need heavier ammo, I use .28s at 350fps, bare minimum!

I use a Guarder Black at +400fps and a stock TM rubber at 350 and below.

If you want to try going back to a stock style nub I recommend the X nub that comes with the madbull red rubbers.

I'd still take the nub out of the rubber though. Make sure you do this as thoroughly as possible, as if you dont, your accuracy will never be any good. If you are not happy you could try removing the locating rib in the rubber aswell, then turn the rubber through 90 degrees, dont forget that the slot in the barrel will need filling aswell or you'll never get a descent seal.
 

·
Registered
Joined
·
23 Posts
Dang, .28s at 350 fps? I run .2(gonna upgrade to .25) in my 400fps ak and honestly, I still get nice accuracy. I guess I would get better accuracy with heavier bbs. Anyways, setup looks good but m130? Won't that get you at like 440? Is that for the field limit? And by the way, how do you like that king arms gearbox, I was looking at that and it seems like a good bang for the buck.
 

·
Registered
Joined
·
37 Posts
Discussion Starter · #7 ·
Tried Blaster 0.3s and I now have more stability/consistency in the way that my bbs now consistently take a right-ish flightpath, so there is improvement. I can get 10/10 body shots at 50m, but i don't want to be calculating drop, wind AND this weird effect.

I'm starting to think there's either an alignment problem between the upper receiver and the outer barrel, or the outer is slightly rotated CW. Will take out gearbox and hop chamber + barrel and stick them in my G&P (since the G&P mur-1 upper and the Dboys lower are not compatible). It's all getting kind of ridiculous.

@jeffrey: I'm quite satisfied with the gearbox, individually, the parts are great but the combination isn't perfect for a DMR. Also my field limit for DMR is 140m/s but the M130 was lying around so..


- LE:

Turns out the problem was with the Dboys outer barrel - upper receiver. It was either crooked, or held the hop-up chamber tilted or something. As soon as i put the prommy chamber + madbull 509mm tightbore in my g&p sentry, it jumped from 114m/s to 127m/s and the bbs flew straighter than ever.

Installing the systema m130 spring got me to 136m/s, which is perfect for my field limit. I'm waiting for the wind to die down so I can determine my effective range.
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top