A Nightmare M4 DMR Build

[tskeleton]

Hello AP! So basically I got a custom m4 DMR build that was a work in progress off of a friend of mine. Turns out there are quite a bit of problems with the gun but I'm hoping to work out the kinks and have one beast of a gun. Unfortunately I have little experience with airsoft tech work so I have a couple q's for you guys.
1. The gun has an m130 spring in it. The motor seems to be a stock jg motor and has a hard time pulling it but it manages. I also have a madbull ultimate hopup unit installed. For some reason, bbs seem to get stuck inside the hop-up unit. Could it possibly be the weak motor? Or is something else causing this?
2. The selector switch, dust cover, and charging handle came off of a jg s-system. They are on the new dmr's metal madbull noveske body but don't seem to fit. The dust cover is to small, the selector switch doesn't click into place, and the charging handle doesn't pull back. Could someone link me a good m4 body pieces kit or recommend a solution?
3. I'm not sure if this is the right place to ask this but I didn't see any airsoft shop/tech section on this forum. I was wondering if there were any official airsoft tech shops or even just airsofters who know they are doing in South Oregon (springfield/euegene area)? I'm feeling I might just want to hand this off to someone who knows what to do.

[Payback]

That motor will eventually fail early. You need a good high torque motor.

The hopup is meant to keep bb's in it when the mag is pulled out. There is a little O-ring on the bottom. If you don't like this function, remove the o-ring. If they are getting stuck inside the tube where the bucking is, then turn the hopup off (raise the hopup). They are getting blocked by the bucking.

The body parts are usually listed in the "other" on websites for external parts. The charging handle is either riding on top of the gearbox, or stuck on something.

It all seems to be fairly easy fixes tho. Just tuning a tweaking. Sometimes a drill and a small bit is the fix.

[tskeleton]

Yeah just picked up a matrix high torque, but the pinion gear seems to be a bit to big for the gearbox so I'm just waiting for a smaller one to ship. The hop up is off and I took off the o-ring but the bbs keep getting stuck right at the intersection of the "T". As for the charging handle, it is rubbing on the top of the gearbox. Would sanding a bit off the top of the gearbox case be alright, or will it affect it?

[Payback]

I have the same motor. I just used a drill bit to open up the hole on the gearbox a little more. It's not a stress point, so a few more mm's wont hurt.

The tabs on the top of the gearbox are for the charging handle. So sanding them down shouldn't hurt. Not sure what else could be with the hopup without looking at it. I have one at home i can look closer at if nobody else has an idea.

[Beran]

How new is the hopup unit? It might just need to be polished up or something. If it''s been heavily used it could be slightly deformed from a bad BB or debris, and if it's brand new it might need to be broken in to smooth out some of the casting marks. I've had new metal hopups that jammed like that before and needed to be lightly filed and buffed.

[CommieHunter]

First, the hop-up and barrel are unrelated to the spring and motor. It sounds like the hop-up issue, if it really is a jam, is due to the installation of the bucking, or a nub that is too large (the MadBull ones often are). It does sound like it's the bucking if they're getting stuck right there.

What velocity are you trying to reach? With the right components, you should be able to get 450FPS (in some cases) with only an M120. An M130 will occasionally be the easier route, if you can't get the compression components right to get that velocity on a lower spring.

With the body, it's really a matter of hand fitting the parts. I've had a MadBull body before, and some dust cover/charging handle parts don't fit correctly. You can either look for scratch marks on the charging handle and file the handle, gearbox, or body, or you can just live with it. If it were me, I would probably file the inside of the charging handle instead of the gearbox shell. While the top isn't really a critical spot, I'd always err on the side of the cheaper / non stress bearing part.