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Discussion Starter · #1 ·
So after following almost everything in the DMR guide that doesn't involve opening the gear box, I have yet to shim the hopup arm on my dboys SCAR.
Before I do that, I was hoping I could have a few things cleared up.

1.) Currently my hopup nub looks like this:
http://www.airsoftpost.com/images/Parts_ICS_MC_17_lg.gif This is very different from the style that Vindi suggested in the DMR post. Is there something inherently wrong with using a nub shaped like this? It definitely has enough strength to make the .3's I want to shoot sail pretty well at 320-330fps, but would it not be accurate enough?

2.) My gun has a tendency to have shots that veer left, right around the time the hopup spin begins to effect the trajectory of the bb. Now this is all well and good for when I want to get hits on those super annoying enemies who like to hide behind trees... but even so, I think I'd prefer having a gun that shoot strait. :-/ Also, this doesn't happen every shot, maybe more like 3/5 shots. This, in my limited experience leads me to suspect the hop arm not staying in the right place, yielding a less than 100% vertical back spin. I checked the arm, and it is slightly wiggly, confirming the stray shots, and with most of them veering left, I think I can assume that in addition to being a little loose, the arm is also favoring a specific side.
So with that in mind, when I go to shim the hop arm, which side should I stuff more shimming on to correct for the veering towards the left?

3.) I had an interesting thought:
Of course, I'll be shooting .3's in skirmishes, due to the increased range and accuracy. However during testing, what if I used .2's? My reasoning is that since .2's are much more apt to be effected by inconsistencies in the gun, would testing with these result in more pronounced accuracy issues,making things easier to diagnose?
 

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Discussion Starter · #2 ·
Hmmm.... I don't want to be annoying or anything, but I've got a game coming up in a day and a half, and I'd really like to get my gun working well before then. Some advice would me most appreciated. Is my question clear enough? I could try to provide some more details if it would help. Thanks :)
 

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Though I'm new to the forum, since no one has offered advice I'll do my best to help out.

1. This is the standard hop nub used in an AEG, so there is nothing inherently wrong in my opinion, though it is not the most consistent shape.

2. Due to the fact that it is not a 100% occurence, I'm led to believe your air nozzle is not seating the bb in the same place everytime, so there may be issues with the nozzle or tappet plate.

3. According to elementary physics, a higher mass bb will be less effected by the sway of hop up so a .2 should show more deviation, however it will also show increased deviation from other variables like wind.
 

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A few things I'd like to add in.

1. Change to an H-Nub, they're more consistent.
2. Shim that hop-up arm, that is probably causing the incosistent shots.
3. Make sure your air-nozzle sets itself in the same place and has very little play horizontally or vertically. They can come slightly loose in the tappet seating as I've learned from first-hand experience.
 

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Sorry 'bout that, I've been off on a coarse so haven't logged on in a while ::)

beison8000 said:
So after following almost everything in the DMR guide that doesn't involve opening the gear box, I have yet to shim the hopup arm on my dboys SCAR.
Before I do that, I was hoping I could have a few things cleared up.

1.) Currently my hopup nub looks like this:
http://www.airsoftpost.com/images/Parts_ICS_MC_17_lg.gif This is very different from the style that Vindi suggested in the DMR post. Is there something inherently wrong with using a nub shaped like this? It definitely has enough strength to make the .3's I want to shoot sail pretty well at 320-330fps, but would it not be accurate enough?

As pointed out already this is what comes as stock in most AEGs. It provides 'ok'ish performance, but nothing more, as also suggested swapping to a H style nub will give a straighter flight path from shot to shot

2.) My gun has a tendency to have shots that veer left, right around the time the hopup spin begins to effect the trajectory of the bb. Now this is all well and good for when I want to get hits on those super annoying enemies who like to hide behind trees... but even so, I think I'd prefer having a gun that shoot strait. :-/ Also, this doesn't happen every shot, maybe more like 3/5 shots. This, in my limited experience leads me to suspect the hop arm not staying in the right place, yielding a less than 100% vertical back spin. I checked the arm, and it is slightly wiggly, confirming the stray shots, and with most of them veering left, I think I can assume that in addition to being a little loose, the arm is also favoring a specific side.
So with that in mind, when I go to shim the hop arm, which side should I stuff more shimming on to correct for the veering towards the left?

If the shot is veering to the left, its because the nub/rubber is applying to much pressure to the left side of the bb, so to correct this, this applies even more so with a H style nub, you need to try to equalize the pressure by increasing it on the right side, to do this you need to shift the nub in the direction of the spin, in your case to the left (IE all your shims should be fitted to the right side of the arm). You also need to make sure the nub sits in the arm flat and level, don't expect this to be a given, as alto have mould lines/poor mould alignment that the nub can sit awkwardly or rock on

3.) I had an interesting thought:
Of course, I'll be shooting .3's in skirmishes, due to the increased range and accuracy. However during testing, what if I used .2's? My reasoning is that since .2's are much more apt to be effected by inconsistencies in the gun, would testing with these result in more pronounced accuracy issues,making things easier to diagnose?

Never, ever test with anything other than the ammo you will be using in a game, it only leads to false readings ;)

Just to follow on from what metallicafastcat and gentlemann said about nozzles, I glue mine in place on the tappet plate using the cylinder head already fitted in the cylinder as a brace for it while it sets, but before you do it you have to make sure the cylinder head/cylinder/hop chamber all align perfectly
 

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Discussion Starter · #6 ·
Thanks for all the help guys! Now I know what to do.

As a surprising and cruel twist of fate, now that I know how to fix the gun... 2/3 body screws stripped!!! Bah! Seeing as how I don't have a dremel or screw extractor here (they're really expensive to buy in korea) I guess I'll be going off to the airsoft shop anyway. Good news though, is that in Korea the service charge is free!
 
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