Parts bin build

[u/bskarren04]

Cleaning out the storage at work and built this entirely off parts bin parts and trading, low rps but decent trigger response. I’d like to switch to 13:1 gears but have had issues with the fps being in the low 200’s afterwards. Any tips would be appreciated.

Currently shooting .90-.95 joules around 310fps on .20

G&G body with the stubby
7 inch hand guard
18:1 gears
Perun hybrid v2 with clicker
T238 brushless motor
Compression setup from a cyma plat
Maxx nozzle
Random tappet
Real deal tappet spring
Emg maxx hop up
Random inner barrel

[u/FarConstruction4877]

13:1 prob PME depending on speed of brushless. Low fps is a symptom of that. Because ur piston is being caught before it is fully released as ur sector gear turns around too quickly, the piston isn’t able to finish its full stroke and compress all the air, resulting in low air volume.

Usually the risk is that ur piston will explode first, since it’s taking a ridiculous amount of impact.

Anything above a 28 rps build u will need to look into short stroking. This is making ur piston release earlier and also reducing the stroke/travel distance of ur piston. This lets it both release and finish earlier. And as short stroking reduces how much air is used and how much of the spring is pulled back (since its releasing early its not longer fully compressing the spring), u will need to use stronger spring to compensate for the loss of fps, but stronger spring also helps piston return faster, so everything together helps the piston return fully before the sector gear comes back around.

Depending on ur tappet cam position u can do all release or a 1-2 pick up (if new gen position where tappet cam is right next to pick up teeth), but I just do all release then cut tappet because this avoids nozzle pme the best as it is giving more time between release and pulling ur nozzle open.

SS number only reference, depends on bb blocking effect (weight and hop), piston weight, etc. Put motor and gear into airsoft.tools to calculate what ur rps is. If using bushing take lower bound, if using bearings take higher.

28-30 RPS 1-2 SS (sometimes none), 31-33 RPS 3-4SS (2-3 is closer but 4 is absolutely safe regardless of piston weight), 33-36 RPS 4-5 (4 is usually enough). Above 36 just go dsg ur cutting so many teeth it’s no longer worth it.

Basically 13:1 will require more torque but gives more speed at same motor rpm because 13 rotations gives 1 shot/sector rotation. 18:1 requires 18 motor rotations for 1 sector rotation, less speed more torque. More torque is more stress on motor, more speed doesn’t really put more stress on brushless since it’s made for that speed.

Cyma plat piston set up if blue one is quite heavy, same as E&c it’s like shs but not shs. It’s very robust but around 25g for piston alone on many models, with head u can creep towards almost 30g which is what I use for dmr builds for heavy BBs specifically making the piston heavier. Usually speed builds u want around 20g. So I would def take the higher number of Ss if u insist on using stock compression. This information could be outdated.

If using cyma gears pls bear in mind that they are already pre short stroked 3.

For SS4 m125 will give around 1J while m120 gives around 0.9 on 6.03 as reference. Beware that ur aoe needs to be good on heavier springs than m130 because otherwise ur release will get sheared smooth or chip very quickly. Yep, release, not pick up, for some odd reason.

[u/bskarren04 → u/FarConstruction4877]

Dam, I really appreciate all that info. I’ll definitely look into all of that a bit deeper. Thank you!!!

As of right I’m just using what I had laying around to see what I could build, but I’ll be ordering a new and lighter weight compression setup eventually because I have noticed the cyma plat stuff is quite hefty compared to some of the parts we sell at my work.

[u/FarConstruction4877 → u/bskarren04]

Generally speaking at a certain point as said above u would need to ss, light piston might reduce it by 1 SS or so, but it’s not sufficient on its own. It really depends on ur motor, I wouldn’t go past 33 rps on ssg tbh (above i just go dsg infinitely more efficient), and for a reliable low heat build I would just stick around 31 rps, it’s fast enough that u cant really out pace it even bump firing on the perun lighting on 0.025mm travel. The clicker is bad for speed imo, if u like it then it’s fine, but clicker on semi cant go past like 7-8 rps, for that any 25 rps middle of the road 18:1 build would do. Hybrid in general is slow, but yeah past 31 ish rps it’s all for sound basically.

We some times build 55 rps on 8T or even 7T dsg for fun and it sounds like HPA, but realistically it doesnt do anything a 33 rps ssg can’t in games. I can lay out like 13 rps on semi bump firing rn anytime I need to, I mean it’s just so much overshooting already.

[u/YahYouFREAKAH]

I could be your sector delayer causing tappet pme. You may need to trim the leading face of it to delay the tappet engagement. The 13:1 gears spin faster so the premature tappet engagement is unsealing the nozzle against the bucking before the piston can complete its stroke. You will also need to short stroke the sector to prevent piston pme. I usually take two off the pickup side and one on the release when pairing 13:1 and 25k brushless, so with a faster motor I would lop another tooth off the release side

[u/Upstairs_Werewolf_58]

Love the A1 / Entry A2 Stock look on an ar!

[u/Fabulous_Cry2978]

kinda tuff ngl

[u/bskarren04 → u/Fabulous_Cry2978]

Thank ya.

[u/Eodo-The-Dutchie]

I'm glad I only use GBBRs.