KA M4 velocity after break-in period

[Maniac Marshall]

Hey all,

Quick question, I recently bought my first replica, a brand new King Arms colt M4.

At the store it was shooting 405 fps with .2s right out of the box, they assured me it would drop after a while.

So far I haven't had many chances to use it so it has maybe 1000 rounds though it, and I couldn't use it at our last game as it was still shooting hot, averaging 402 fps, spiking at 406.

Question is, what's the best way to break it in and will it actually drop enough to game with it, 390 fps would be perfect, but I don't know if that's realistic.

I want this gun for outdoor use only, no cbq, I don't really want to get the spring changed unless it's necessary.

thanks

[Intelligence_Dream]

Try firing it on full auto with the mag out you will see the nozzle moving try to stop it when the nozzle is pulled back so the spring is compressed leaving it like this for a day or two should bring it down a bit.

[venture]

Actually you want to stop when the nozzle is pushed back into the hopup, but before the piston releases.

[Intelligence_Dream]

Ya I thought that's what I said.

[Comeau-SCS]

I know you said you dont want your spring to be changed but it will be the easiest way to drop FPS. Also a lighter spring will require less work from the motor and less stress on the gearbox.

[Maniac Marshall]

yeah, that's what I'm thinking now, so for a v2 gearbox, what spring would bring me to ~375ish fps, and how hard would it be to change out myself?, I have mostly knowledge of paintball guns

[Hectic]

what is the fps limit at your fields? Most places (in ontario) are 400 and 5-10 fps normally wont get a gun pulled from a game. More than that is often pulled tho.
obviously thats always the host or field owners call, but most of the time they will allow a bit of a buffer.

[Maniac Marshall]

the limit is 400, I tried speaking to the owner but even with just 2-3 fps over he didnt want, I was bummed but didnt want to argue more than that

[lurkingknight]

it can take a few thousand cycles for a spring to settle... I would honestly open it up and separate the piston and piston head, see if there is a spacer inside the piston or a bearing.. take it out.. chrono it, it'll be about 30fps less depending if it's a solid chunk or if it's a bearing you can take 2 or 3 pieces out that will drop around 10 fps per piece. For a bearing assembly, first part you take out is the bearing plate. Leave the spacers.

Chrono it after taking the spacer out, then game it... few months down the line, chrono it again. IF it's dropped 20-30 fps, put your piston assembly back to the way it was and now your gun is under 400.

[Hectic]

not to thread jack, but lurking is the fps drop comming from lightening the piston assembly?

[Hectic]

oh nevermind, i get it now, less tenssion on the spring lol. Hurr durr

[lurkingknight]

no when you pull the bearing/spacer out it relaxes the spring a tiny bit so you don't compress it as much.


normally it's fine and dandy to do it when you have a bearing spring guide, it's a bit less desirable to do if that's your only bearing in the compression assembly. But it could save you from spending some money, and it's only a temporary thing in this case.