Odd FPS from new build

[Shirley]

Maybe they aren't "M110" springs...?

Are you using the right kind of BBs? LOL!

[mcguyver]

Load 1 BB into the chamber, remove the mag, and plug the nozzle with your finger (press hard). Does the FPS go up significantly? If so, you have an airleak around the nozzle, escaping back down the feed nozzle.

You can also try to push back on the hop-up to force it to mate better with mechbox, but that one is a little tough to do

[m102404]

Originally Posted by mcguyver

Load 1 BB into the chamber, remove the mag, and plug the nozzle with your finger (press hard). Does the FPS go up significantly? If so, you have an airleak around the nozzle, escaping back down the feed nozzle.

You can also try to push back on the hop-up to force it to mate better with mechbox, but that one is a little tough to do

Thanks! Didn't plug the feed tube by hand...did try the "no-upper hold hopup by hand pressed into mechbox, mag jammed up tight ontop of thigh" juggling thing...no change in low FPS.

When plugging by hand...it wouldn't matter if there was 1 or 3-4 bbs in the feeding tube, right? Objective would be to create a hard seal so no possibility of air loss towards mag...

Shoots nicely for indoor games though...

[m102404]

Another night of fail...

Plugging the hopup = no change in fps

Tried another hopup/rubber/inner barrel combo....seemed to shoot 350fps (w/400fps rated spring) but after a mid cap it dropped down to a consistent 285fps...

I'm down to swapping mechboxes & bodies with a known-good AEG to determine if it's some weird fitting issue with this setup.

[CDN_Stalker]

Originally Posted by m102404

weird...just plain weird...

Rebuilt the mechbox...new piston, piston head, cylinder head, nozzle...400fps spring, Guarder black hopup rubber/nub, KA hopup unit, different M4 inner...best it'll do is a meager 330fps...

I swapped a complete new upper onto it...systema hopup, 6.01mm 300mm short inner...shot 330-ish...

Tried my upper on another lower (that should shoot 350)...and it shot just under 340fps....

Confused...but resisted the urge to chuck it against the wall...so at least the evening ended ok...

Lol, you sound like me swapping various CA M24 parts around in my rifle, try a combination out, chrony, swap a part, chrony, recording what is in there. Luckily I have two piston heads, four pistons, one with an O-ring head, two non-bearing spring guides, a bearing spring guide........ five springs, 7mm and 9mm............. ya, at least it's way easier for me to swap parts, and it's good to do since I end up with a variety of combinations for use at various games (340fps, 370fps, 400fps, 430fps and 490fps....... cut my 585fps spring since it's barely usable anywhere except the huge annual desert game).

[hebet]

Sounds like my issue with my MP5 You still have the Mask piston head and cylinder head installed. I'm going to take mine out and see if my 209FPS can go back up to 350. I also might change out the cylinder and experiment with different port positions.

[m102404]

Nope...the mask piston head and cylinder head have been out of this build since the 2nd tear down...

[hebet]

Originally Posted by m102404

Nope...the mask piston head and cylinder head have been out of this build since the 2nd tear down...

Didn't like them eh?? I'll be getting those parts together then you can pick and choose what you want

[coach]

Originally Posted by hebet

Didn't like them eh?? I'll be getting those parts together then you can pick and choose what you want

nothing wrong with the MASK piston head. (the white plastic one) you do need to replace the white silicon oring though. It's too big and loose. The current batch and the new aluminum ones have had the white orings replaced with a black one. Alternatively, you can also use a standard black rubber oring.

[m102404]

I'm still undecided on the MASK setup...but with the FPS issues, I wanted an "old-fashioned" baseline. If I get this running properly, I'll swap out parts and sub in the MASK components.

Just bought a Systema mechbox shell last night...so now I'm really in the RED on this project...

[m102404]

I transplanted all the parts from the Guarder reinforced shell...to a Systema shell....and that seemed to work.

It shoots as expected now.

The systema selector/selector plate is wonky like the other one that was on the Guarder shell (Deepfire)...when in this body.

So I'd conclude that there's a definite incompatibility issue with this KA body and at a minimum this Guarder reinforced mechbox. There's also something wonky with more than one type of selector plate with this body.

It's a pretty setup...but what a pain in the a**.

Tys

[Crunchmeister]

Originally Posted by m102404

The systema selector/selector plate is wonky like the other one that was on the Guarder shell (Deepfire)...when in this body.

Just for your own personal info here, I've got CA selector plates on both a Guarder and Deepfire reinforced shells and they fit perfectly and they work great. Nice smooth action on both. I know CA doesn't come up often as an "aftermarket" part where people prefer the higher brand names, but I tried a Systema selector plate on both those shells, and both were tight and didn't work quite right.

Happy to hear you got your problem sorted out though.

[Donster]

so with the new mechbox, and the proper FPS settings, have you reinstalled the MASK stuff or no?

[m102404]

Not yet...I'm going to leave the setup I have as is for a week or two...I want to game the FTF game on the 25th with it to stress test it. Then I'll tear into it again and swap back in the MASK piston/cylinder head.

Here's a couple of pics of what I've finished off for now. This is the M4 that finally shoots...the shiny thing is a CAPS pistol I've had on the go for some time now.

[Styrak]

Ah, another problem with Guarder crap parts...