Arcturus NY06 Review and Build Thread

Quick update on the build side of this: I‘m at 85% completion… for now. The hop unit has been partially tuned, and I replaced the barrel spring with a piece of cork, which provides more consistent pressure. Unfortunately it’s icy as frick right now, so I haven’t been out long enough to do good shooting tests, but once I do I’ll check barrel on the barrel setup and my review of the stock parts. Aside from the chamber packing, I’m still interested in exactly what I can get out of the stock setup with just an aftermarket rubber. Currently my ammo of choice is G&G .25g, which is great since the barrel voluming works out well, but I’ll at least be doing tests to see how this performs on .30g and upwards.

The major issue still in the works:

Despite having lightened my piston to 20.5g, I am still getting PME w/ an 11.1v @ around 30 RPS w/ .25g. This feels like I’m missing something, since myself and others have absolutely run similar setups without any PME issues. Tomorrow I’m going back into the gearbox to go through everything again and continue tuning. It’s rare that I get everything right on the first try, and I tend to find that the more times I work though something like this, the more refined the gearbox will be.

I’ll be checking for:

Piston drag on the GB rails (maybe polish them with some metal polish anyways), and I’ll be removing all lube on the rails, testing, and relubing with different lube (I use some different stuff). The Arcturus piston is a chunky fella and it’s possible I missed something when I checked the tightness last.

O-ring drag on the cylinder. I’ll be doing a manual check, cleaning and regreasing, and then maybe change for a buna-n ring I have around, or even trying a different piston head, depending on how it feels.

Spring binding. It has recently come to my attention that the Arcturus spring guide is actually faulty. The bearings do not rotate properly. As such, I’ll be testing different springs with a Specna Arms (I think?) QD spring guide that‘s compatible to make sure it’s not the guide’s fault.

To clarify, the gun hits PME with the stock M120 spring, and a PDI 170% I tested. PME goes away on a PDI 190%, which is roughly an M130 (gives 410 w/ .20s 3/4 cylinder and 380mm barrel). One note is that the spring gives me a bit less energy than it did in the other build, and with the little bit of inefficiency from using .20gs to chrono, I’ll probably be under 400 FPS on the 190%, so the gun will actually be field legal as an ordinary assault rifle, which gives me the choice to just roll with it as-is and ignore the PME on M120.

The question now becomes, do I really want to do that? I’m very confident the setup will handle the M130, but I’m not sure I want to give up yet on fixing the issue, especially since if I ever wanted to run a barrel longer than 265mm I’d have no full auto, since my power would go up, I‘d have to bring the spring down, and then I’d have PME again. Or I’d have to deal with running it as DMR class. While not the end of the world (15 yards MED), it would ruin the real reason I have this replica: run and gun! Move and shoot! So at the end of the day, it would be pointless.

I also have the option of giving up RPS via the motor’s handy potentiometer, but I don’t want to do that. Not yet at least.

Okay, final post to wrap up this thread (for now). I’ve put the gun through another game day and everything seems to be holding up and functioning nicely, so I think it’s safe to say my work is done.

Current stats:

28 RPS

1.5J

Effective range: 65 meters ish? I haven’t done anything resembling an objective test yet.


Here’s the current list of mods and parts:

T238 33K BL motor (tower bearings lubed with ceramic bicycle bearing grease)

PDI 50 degree W-hold packing

Guarder tappet plate

PDI 190% spring

Piston assembly lightened to 20g (attempting to address PME)

Gears reshimmed (too tight factory)

Cylinder polished (why not)

And then I’ve done some basic stabilization on the hop and barrel group.