Modify srock Systema cylinders (M90, M150, etc)

[kengel]

Edit: Dammit...I noticed the "srock" typo in the title as I was clicking on "submit". It should, of course, say "stock"

I have my PTW assembled and ready to roll just in time to watch the outdoor season disappear. I guess that means I'm switching my focus to CQB.

The problem I'm trying to dance around is that even the Systema M90 cylinder is 10-20fps above our indoor field limit (400fps).

I'd like to create my own home frown M80 equivalent.

Anyone know if the spring inside the factory systema cylinders are swappable with standard systema (or any other) springs?
If so, has anyone got first hand experience doing this? Any detail would be appreciated (spring type, fps achieved, reliability, etc).

Thanks

[trevor]

here is what the cylinders are expected at:
M150 cylinder: 505-510 FPS
M130 cylinder: 428-432 FPS
M110 cylinder: 387-389 FPS
M90 cylinder: 330-335 FPS

a M90 should fit well into indoors

[mcguyver]

The springs inside PTW cylinders are not compatible with standard AEG springs. The diameter of PTW springs is smaller.

You can get a spring for an APS and cut it down to make custom velocities. SBranson23 has done just that. Perhaps he'll chime in here and give you the details.

But for CQB, my M90 shoots 285 fps with 0.25g BBs, so you should be fine with 0.20g.

[Griffin]

Originally Posted by trevor

here is what the cylinders are expected at:
M150 cylinder: 505-510 FPS
M130 cylinder: 428-432 FPS
M110 cylinder: 387-389 FPS
M90 cylinder: 330-335 FPS

a M90 should fit well into indoors

I take those FPS readings are with a .20g bb. So would it be possible to use lets say M110 with a .28g bb instead, and M130 for outdoor use with a .25g-.28g bb to lower the FPS.

[Daes]

Originally Posted by Griffin

I take those FPS readings are with a .20g bb. So would it be possible to use lets say M110 with a .28g bb instead, and M130 for outdoor use with a .25g-.28g bb to lower the FPS.

Unlike Paintball, Airsoft is more worried about the joules. That means the FPS of 400 is measured for .20g's, thus using heavier weight will mean less FPS and the club will NOT allow you to bump it back up to 400fps with the said heavier weight.

[Griffin]

Originally Posted by Daes

Unlike Paintball, Airsoft is more worried about the joules. That means the FPS of 400 is measured for .20g's, thus using heavier weight will mean less FPS and the club will NOT allow you to bump it back up to 400fps with the said heavier weight.

I am sorry I don't really understand what your trying to say but, Ill take a guess. Basically than if I used a heavier BB for example with a M130 cylinder and the FPS was reduced to below 400, I would not be allowed to make tweaks to the gun to get to shoot 400 with that weight of BB correct?. Now if .28g reduces the fps of M130 between 400-420 FPS wold I be allowed to play with that setup, or are you saying that when being Chrony'd it has to be done with a .20g bb.

[Ace of Spades©]

Usually before a game, the host will get you to chronie your gun to make sure it is compliant with the regulations of that game. They will always make you use .20g bbs to make sure you are not running a hot gun and using say .30g to bring it down to the 350 fps limit.

[Griffin]

Thanks Ace cleared that up nicely for me.

[kengel]

I've heard conflicting stories, but the indoor limit at Trek in Calgary is either 300 or 320 fps. The M90 cylinder is definitely above that so it looks like I need to be looking at getting a spring cut down.

I know I know...I could probably get away with it as nobody chronies their guns before play, but I also know how much it pisses me off when a get hit in the sensitive junk by a hot gun...I figure I better lead by example.

[mcguyver]

Isn't Trek semi-only? If so, you should be fine with the M90. All the other PTW owners in Calgary use the M90, and I'm pretty sure none of them have chopped a spring.

[kengel]

Edit: Oops...misread what you guys were saying above with regard to bb weights. I agree with what you are saying so disregard this post.

I don't think the reasoning behind "just run a heavier bb to reduce fps" is sound from a physics perpective. It may reduce fps but it will essentially hit with the same force (approximately), and that's really what the fps limits are trying to address.

I forget the actual equation but I'm sure it's been discussed in other threads. Someone can correct me if I'm wrong.

I've seen guys running some pretty hot guns indoors and they tend to load them up with .3's or higher thinking that they are being safe because they're reducing their fps below the limit. Wrong wrong wrong.

Anyway, back on topic.

Anyone else ever modify their stock cylinder?

[kengel]

@Macguyver

Yup, Trek is semi-only but there are fps limits that the JOC crew have defined which are less than the M90.

[mcguyver]

Considering that there are about a dozen or so guys in JOC that have PTWs, I think you'd find the M90 sufficient. But ask Kimbo or ThePirate what they use.

Look here:

http://www.systema-europe.com/Forum/...s.asp?TID=1049

[SBranson23]

Yup, as mcguyver said, an APS spring is the right diameter if you want to use a custom cut. I was working towards a 400fps or M120 spring so I started with the APS180. If you need 300 and don't really need the 320-330 or so of the M90 (mine shoots 328fps almost every time), I just suggest you cut the spring in your M90 down to an M80. Just cut a coil off, heat the end and bend it flat again and chrono it. Keep going until you get the FPS you want. It requires patience 'cause you don't wanna end up with an M75 if you don't have to. Very easy to do.

[Daes]

Here is a flip question, anyone tried to pop in a higher than M150 spring? Bring it up to M170 - M190?

Under law, keeping under 5 joules or so, a M200 would be feasible, completely non-playable, but just to test the limits of the planetary gears?

-Daes