KJW M9A1, inconsistent hop-up?
 

'Evening. Bought the pistol brand-new a few weeks ago and have since been able to take it out for some plinking. I've noticed that around 60ish feet, the BB's seem to drop to the ground or fly straight up- with very few going relatively straight the whole one-hundred or so feet of my yard. Now, obviously I've taken the slide off and everything looks to be in order, the bucking isn't torn or the like and the barrel is secure and clean. I've been using .2 and .28 bb's, both have the same results. I'm at a complete loss here.

just to be sure, your bb's are randomly going up or down? Nothing consistent?

are u sure its the hop up? remember these are airsoft with round ammo its not going to go perfect everytime there will always be some movement( even more so if there wind or something)

Exactly. Three shots will drop, the next four will go straight up, the next two will go straight- I've got no idea what the deal is. I cleaned the inner barrel/rubber again as per a suggestion, but the problem persists.

Pretty damn sure it's the hop-up. When it goes up, it doesn't simply veer, it makes a steep climb. And that's using .28 bb's. When I lower the hop, they just drop 30 feet in front of me.

Can't say i've been a fan of KJW quality. Its really hit and miss with their products.

Strip down the gun and barrel assembly and clean out any excess grease. I find a lot of KJW guns are either packed incredibly greasy or dry as hell. Not sure how yours were but there could be excess lubrication on the hopup itself, which will give you inconsistency.

Just remove the hopup, wash it in soapy water and let dry. Reinstall after that and see what kind of results you are getting.

Could also be from the fps variation that comes with a gas gun as it nears an empty tank.

Hop rubber could still need to be broken in. Could just be a crappy rubber.
I know the rubber in my kj m9 vertec has served me well for years but not all of em are great. Also what weight of bb are you using. I use 30 in all my gbbs they like heavy ammo

Well, to me it looks fine. The hop-up unit didn't seem to be bathed in grease at least. Gutted and cleaned the entire unit just to be safe, though... still getting the same consistency (or lack thereof) as before.

Been testing it out with .2 and .28's, more so the latter. I'm starting to think that the problem is indeed the rubber... I'll try to switch it out in the next few weeks and see if anything changes.


Thanks for all the help and suggestions, guys. I'm sure I'll have this sorted out yet. :D

Is it a new KJW M9? Older ones had a fixed hopup.
Just some information.

Figured I might as well bring some closure to this thread. I replaced the stock bucking with a 50 degree 'Maple Leaf' rubber, and it seems to be doing wonders. Shots are now nice and straight within the effective range. Haven't decided if I'm going to run .25's or .28's, both seem to be working at the moment.

All in all, I'm pretty impressed for a $6 fix. Hopefully it will continue working up to snuff for the next season.