More problems with my dpms M4.

[NoGear]

mabie ur hopup adjuster is broken

[theguy]

Originally Posted by NoGear

mabie ur hopup adjuster is broken

Good god please stop raping the English language!

[Skladfin]

Your hop up nubbing is missing. Nothing to do with gearbox whatsoever.

And the O-Ring on the airseal nozzle is inside the nozzle, it's not on the outside, that's why you didn't see it.

[Janz99]

Well, i can assure you the hop up bucking is definitly there. Its possible that the bucking isnt functioning properly, but i also doubt that. If i remove the barrel and look inside the hop up unit, i can see the bucking pushing the hop up rubber into the barrel.

Ive tried adjusting the hop up all the way to the max. and it actually seems to make the problem worse, almost like its putting the wrong spin on the BB lol.

On a decent m4, what kind of range should you be able to see before the BB's start to arc down to the ground?

[Styrak]

Originally Posted by Janz99

On a decent m4, what kind of range should you be able to see before the BB's start to arc down to the ground?

100 feet.

[Janz99]

Is that with or without any sort of hop up adjustments.

[Dynamo]

was one of your upgrades a new cylinder?
i was having some FPS issues with my gun for a while.
i was using a new systema M120 and getting no more than 300fps.
turns out that i had a non-ported cylinder, so i was getting "suckback", as the piston was pulled back, it would cause a vacuum and suck the BB back slowing it down.
now that i replaced the cylinder with a ported one, im just under 400fps.

[AngelusNex]

Originally Posted by Dynamo

was one of your upgrades a new cylinder?
i was having some FPS issues with my gun for a while.
i was using a new systema M120 and getting no more than 300fps.
turns out that i had a non-ported cylinder, so i was getting "suckback", as the piston was pulled back, it would cause a vacuum and suck the BB back slowing it down.
now that i replaced the cylinder with a ported one, im just under 400fps.

That makes no seance. it's vise verse. ported with long barrel = suck back, non-ported with short barrel just maximizes damage caused to mechbox shell.

[Styrak]

Originally Posted by Dynamo

was one of your upgrades a new cylinder?
i was having some FPS issues with my gun for a while.
i was using a new systema M120 and getting no more than 300fps.
turns out that i had a non-ported cylinder, so i was getting "suckback", as the piston was pulled back, it would cause a vacuum and suck the BB back slowing it down.
now that i replaced the cylinder with a ported one, im just under 400fps.

That's incorrect. An unported barrel would just cause your BB to be pushed by air that would otherwise be blown out the port, and not maximizing the air usage in your cylinder. The BB has already left the barrel and the piston has not completed it's cycle so it's wasting air.

Basically, the port is there so that after the piston passes the port, the entire volume past the port can be used to push the BB.

So it WOULD cause the FPS loss you're talking about, it's just your methodology is wrong

[NoGear]

Originally Posted by theguy

Good god please stop raping the English language!

dude quit flaming not cool.

it could be that you put the reciver back wrong (like i did once XD)
if you cleaned your barrel and forgot to turn off the hopup you might of broken it and it needs to be replaced

[Janz99]

I didnt change the cylinder. The parts I changed are:

-piston head, to a ball bearing pistons head
-spring guide, to a ball bearing spring guide
-air tip/seal nozzle
-spring (s120) which i had to take out due to the stock motor not being able to compress it.
-new hop up rubber (which also had to be taken out due to jamming issues with it)
-re-shimmed gear box
-tightbore barrel

Ryan

[NoGear]

you may have wreched your motor when trying to compress the s120 spring causing the drop in fp range and possibly accuracy. it could also be the cylinder might be damaged or causing a leak

[Styrak]

Originally Posted by NoGear

you may have wreched your motor when trying to compress the s120 spring causing the drop in fp range and possibly accuracy. it could also be the cylinder might be damaged or causing a leak

Motors don't affect range or accuracy. And highly unlikely that the cylinder is "damaged". Don't give out bad advice.

[Janz99]

The motor spins just fine. I took it out cleaned the brushes and armeture and inspected everything.

I did happen to open up the mech box again tonight to have a thorough look at everything. So here is my what i have so far:

-first thing i noticed is that 2 of the 3 gears are shimmed way to tight. When i did the shimming i only held the two cases together by hand, but didnt check it when it was actually bolted together. When bolted, the gears barely turn by hand.

-second thing i noticed, is that without the air nozzle in place and the piston in the cylinder, if i cover the hole, and pull the piston out of the cylinder, there is almost NO vacum/resistance when pulling it back. It almost seems like the oring that came with the piston head isnt quite large enough and doesnt seal against the cylinder. Is it suppose to be like this, or should i start playing with o-rings untill i get a good seal?

-i did have a look at the air nozzle again, and i do see the small oring inside the nozzle. again, i really think the oring could have been larger creating a better seal on the nozzle, but i guess ill have to live with it.

So im now wondering if all my problems were completly caused by to tight of a shim job? Im also wondering if this is the reason why it wouldnt compress the s120 spring all the way, and would only compress the stock spring.

Ryan

[Mitchell12]

Originally Posted by Styrak

No, it's really not that accurate.

I didn't say it was accurate, I said it was vague. It gives you a basic idea of if you've at all increased your fps or decreased it accidentally. Never did I claim it to be accurate though I would argue it's consistency, Sorry for slightly deviating off topic.