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Grant
04-07-2007, 02:14 PM
I want to achieve a very high ROF in my CA SCAR Light. I think I am going to use a Systema Turbo motor, some sort of high speed gears and a 10.8v 30amp battery.

Is there any chance that the piston will be pulled back before the previous BB exits the barrel causing suction and slowing down the BB? The Barrel is 384mm. That is a little longer than your normal M4 (363mm), but shorter than an M16 (510mm).

Thanks!

Grant
04-07-2007, 02:25 PM
I figured it on paper, and it really does not seem possible, but I could be doing something wrong.

shakman
04-07-2007, 02:28 PM
Congratulations! You're well on your way to having a ROF in your gun that NO magazine will be able to keep up with.

Let's forget about the "suction" problem you're addressing and look at some more obvious things.

1. ROF that high does exactly 3 things: a) wastes BB's needlessly. b) Eats your internals prematurely. c) See point b.

2. There are several people in this community that own the CA M15A4 CQB. With a 9.6v 3000mah crane stock battery and an M120 spring, most owners still complain about their magazines not being able to keep up with the cyclic rate of the gun and the guns subsequently "shoots blanks" at the most inopportune moment. In fact, I've had conversations with some owners about dropping in high-torque gears to slow down the ROF to something the magazines can properly feed.

My point is this: If you run high speed gears with a 10.8v battery, you're asking for nothing but problems down the road.

Now to address your question...

There is a *good* chance that the piston will begin to retract before the BB has exited the muzzle especially in the proposed configuration you've outlined. Just add that to the list of why you shouldn't do what you're proposing to do.

Just my 2 cents....

AustinWolv
04-07-2007, 02:39 PM
Ah, the obsession with ROF for some reason. Quality mags can keep up with insanely-fast ROF, such as standard mags and TM hi-caps.

No, you don't need to worry about suction. What you need to worry about is ripping up your piston because it isn't all the way forward before the gears come around again.

You'll want to short stroke mod the piston.....cutting a tooth or two off the end of the sector gear's rotation will release the piston sooner. It isn't scientific, but expect to lose roughly 10fps for every tooth you remove, give or take.

Grant
04-07-2007, 04:16 PM
Yea, I am familiar with the internal consequences of insane ROF, and some of the tricks to subdue them. (A few of my teammates also enjoy insane ROF)

I will probably not be using the high speed gears, I just said that to make sure I would be well under the ROF needed to make suction.

Thanks for your time and input.

SilentVectorX
04-08-2007, 01:13 AM
You would need to hit approx. 312RPS to 'suck back' a BB in a barrel that long at 400FPS. Not gonna happen.

Shakman; well I guess CA highcaps just plain suck then ,ne? Common sense says... get better magazines. I thought you were a techie? 10.8's aren't scary. 14v Lipos are.

A Systema Turbo, HS Helical gears, Promy piston, M100 spring and 12v3800 IB pack gets me 38RPS in my G36S Pro. Haven't chonoed, and I still need a MOSFET switch. Oh, and I use MAG midcaps to feed the beast. Reliably.

Go for the HS gears. They're 13.8% faster than stock ratio, and it gives you an excuse/reason to buy Prometheus. If you bump up the spring tension, you can forgo the SS mod. With an M120 spring, G&P HS motor, Promy HS gears, and a 14.4 nimh, I didn't get any sector clipping. I broke a guarder piston in half (thanks to a pistonhead vibrating loose... shoulda taken the 15 minutes to locktite the SOB) before I got to record the RoF, gotta wait for some better parts to get here before I try again.

The only way to learn (short of cheating and having a tech teach you everything), is trial, error, and experimentation. Having an engineer look at broken stuff does help though. :D
-SVX

AustinWolv
04-08-2007, 08:40 AM
Conversely, one could learn how to use semi-auto, double-tapping, and short bursts on FA, because that kind of ROF is really great for overshooting people!
Yes, let's teach everyone, including the inexperienced, how to have each and every replica be a BB dumpfest tool with drum mags on everything. That really contributes to the mindset of a milsim atmosphere versus paintsoft spray'n'pray.

Lame.

SilentVectorX
04-09-2007, 01:57 AM
PMs sent.

Last time I did a SS mod, it dropped me 10M/S per tooth. That's a big drop! I ended up getting 80M/S out of an M100 spring IIRC.

-SVX

Dirus
04-09-2007, 12:06 PM
If you chop a few teeth from the sector, the stroke is shorter. Maybe you can put a spacer on the string guide to make the spring a little stiffer. Just a thought.

Grant
04-09-2007, 07:03 PM
Conversely, one could learn how to use semi-auto, double-tapping, and short bursts on FA, because that kind of ROF is really great for overshooting people!
Yes, let's teach everyone, including the inexperienced, how to have each and every replica be a BB dumpfest tool with drum mags on everything. That really contributes to the mindset of a milsim atmosphere versus paintsoft spray'n'pray.

Lame.


Well, I mostly wanted the ROF to 1. Be really cool. and 2. A high ROF really helps when you are shooting through evergreens. (Which our field happens to be dominated by)

So, really it is not taking away from the milsim, it is allowing me to shoot through trees...