Maruzen (spring)M870 adjustable hop mod...

[Docv400]

Had a search and couldn't find anything on this being done before, so if anyone's interested I'll post a little 'how-to' later (I'm at work now) with some pretty pictures

[Five-sEvEn]

Isn't the spring M870 the CA870?

If that's the case, then there's these hopup spring things that were being sold at one time that you could kinda use to adjust hopup. I forgot what they were called, but they might've been manufacturered by ANGS or something.

 

Ahh found it.

http://www.angs.co.jp/98_45.html

Not that you can read any of it though...

 

And since that doesn't give you the picture

go to: http://www.angs.co.jp/

Look for the box that says keyword, or at least something that looks like a search box, and type in "ca870" and the second result will be your hopup springs.

 

Hope that helps!

[Docv400]

Isn't the spring M870 the CA870?

<{POST_SNAPBACK}>

You may be right about the name, but having to strip the barrel out to adjust the hop is just plain crazy for such a pricey springer.

[Five-sEvEn]

If it's not the charger, then that's what you have to do. The CA870 isn't meant to have adjustable hopup. The only CA870 I know that had adjustable hopup is the Charger.

[cazboab]

Also, the Maruzen costs £70, not 250, what you're dealing with is a VFC.

[Five-sEvEn]

I any case, aren't the VFC M870's based off of the CA870 design, only with a metal body and power upgrades? Or something like that?...

[cazboab]

Yeah, except the hop on any Maruzen I've used worked.

[Five-sEvEn]

Hopup on the VFC guns don't work?

[Docv400]

The CA870 isn't meant to have adjustable hopup. The only CA870 I know that had adjustable hopup is the Charger.

<{POST_SNAPBACK}>

That's the whole point of this topic. I've modded a non adjustable hop to be adjustable.

And it doesn't really matter what it's called. It's a Maruzen spring shotgun, all metal (except for grip and charging handle) and has a fixed hop (which sucks for such a powerful gun)

[Five-sEvEn]

So why the long posts about not particularly relevant stuffs? Post the how-to already!

[Docv400]

What you'll need;

Maruzen 870 spring shotgun (with non-adjustable hop)

4mm tap and tap-wrench (locking pliers will do)

4mm grub-screw (approx 6-10mm long)

1 X 2mm ball bearing (optional)

5mm drill

Allen keys

 

OK. Take your non-adjustable hop Maruzen spring shotgun and remove the outer barrel by unscrewing the end-cap (at the front) and removing the two tiny grub-screws at the rear of the barrel tube. The outer then pulls off.

On top of the body where the inner barrel fits is a small round sticker which holds in the hop spring and plastic bucking piece. Remove it, and tip the gun over to get the spring and bucking out. (Hole 'A')

The inner barrel is held in by a 'roll' pin (in hole 'B'), push/tap it out with an allen key, pin-punch or small screwdriver.

Pull the inner barrel out carefully, being careful not too lose the (easily lost ) hop rubber.

You now thread hole 'A' with the tap, right through.

Drill a 5mm hole in your outer barrel in-line with the freshly-tapped hole 'A' in the body.

You can hold the hop rubber secure with a piece of tape but it has to be really thin because of the tight fit of the hop assembly in the body.

Refit the inner barrel and hop assembly (watch that rubber, it's tiny and it's not impossible to fit it the wrong way round. Check the shape of the cut-out in the plastic hop sleeve, the rubber matches it)

I superglued a ball bearing to the hop adjusting grub screw but it's not strictly neccessary.

Reassemble the gun, and lastly, screw your 4mm grub screw into the hole you tapped, through the hole you drilled.

Screw it in carefully whilst looking down the barrel, with a light shining into the magwell so you can see when the hop rubber starts to protrude into the barrel.

Back it off half a turn and load up your favourite BBs and go play. The adjustment is direct (not geared like an AEG hop) so it's very sensitive, adjust an 1/8 of a turn or less at a time.

 

 

I think that covers it...if something doesn't make sense, just say.

[Docv400]

P.s.

I also added an O-ring ('B') to seal the end of the hop assembly to the inside of the body where the air nozzle pokes through ('A').

It means machining a bit off the plastic hop sleeve, which is difficult without a lathe but if you have one available...

Couple of other pics...

[Five-sEvEn]

You sir deserve a +1

[Five-sEvEn]

DOUBLE POST

[Docv400]

Thanks...