Non-consistant firing, possibly HOP unit?

[doc_pathfinders]

Lo' all..

i have an unusual case, and i was wondering if anyone could offer sage advice:

i have a DBOYS SPR MK12 MOD0, which i have put a full systema gearbox in, replaced the HOP unit with a NEO unit (http://www.airsoftgi.com/product_inf...oducts_id=5625) and madbull RED Bucking. (plus a prometheus 6.03mm IB) plus i replaced the magazine catch with a G&G version.

The FPS is great (so no sealing issues, it fires exactly what it should)

BUT i am getting a 20-30% rate of 'no projectile' shots (that is, i pull trigger and nothing comes out) i can have a string of 9 shots perfect and then it'll drop 3 shots, but more usually i'll have 3-4 'good' shots and then a dropped one etc etc..

I have tried other magazines and some seem a tad more reliable, but none really give acceptable service (i've tried hicap, midcap and real-cap magazines)

i have a feeling that it's due to the HOP unit, does anyone have experience with the hop unit i'm using? that or it's due to the HOP bucking..

my next step is to modify the DBOYS hop unit to fit the systema gearbox (yes, the tolerance's are that far out that i need to dremel it a bit) and after that try an old 'normal' hop bucking.

anyone have any insight on this? it's unusual that i'm getting the sporadic feed issues without any sealing problems..

[Amos]

It's the madbull rubber.

Scrap that and get something good like an Airsoft Research Syndicate rubber, or a Guarder Clear

[doc_pathfinders]

yeah? damn, the madbull looked so sexy as well..

any ideas or theory on why it's happening? have you had this happen to you before or is this well documented?

also, cheers for that amos, i'll stick to guarder clears (fav brand, just wanted to try somethgin different)

[Amos]

It's pretty well documented...

The madbull rubbers suck all around... unless you're the 1 in 20 person that it actually works properly for.

[doc_pathfinders]

excellent, now to correct my foolish mistake.. i'll stick to what i know works in future.

after i'm done i'll report back what is happening, thanks Amos,

[doc_pathfinders]

Nope, not the hop rubber.

But i might have found the problem, when i adjust my hold on the magazine i get different results. held forwards i can have 100% fail to feed vursis 15 percent when held back.

i'm guessing its due to shortness of the feed tube..

next i will mod the DBOYS to fit the gearbox.

[BABU]

keep in mind it could be anything causing this problem, i had the exact same problem you are describing except on my G&G mp5, i had done some upgrades, put in guarder clear, shimmed the gearbox, and put in a full metal cylinder head instead of the stock plastic one.

after i did this it would randomly with no trend fire blanks, i also tried different types of mags and the problem continued, i knew it wasnt a mag problem as it shot fine b4 i did the upgrades

after replacing parts bak to stock and then trying one by one i figured out that the reason for the misfires was the cylinder head, dont know why, i have no clue how the cylinder head would affect a bb feeding into the hop up, as i did test and the feed nozzle did slide fine with no problems, but for some reason as soon as i put the stock plastic one in everything went back to normal

although i did try applying pressure to my mags in different directions and that didnt change anything at all, so if you adjusting the mag is giving you different results then something in that area is probably the source of the problem

i know this isnt of much help, just figured id share my experience with you so you know to keep an open mind, something you may think is not the problem, might actually be causing you all this hassle

[Blackthorne]

May be a silly question but after you get a misfire does the next shot roll out 2 BB's?

Fail to feed and fail to fire are two different things.

I agree however the documented issues with MadBull bukings are likely to blame.

[doc_pathfinders]

Blackthorne, can't be the bucking because i replaced it with a no-name brand that i had around.

and also, i have a failiure to feed, as in the bb's are being stuck up bastards and not wanting to be shot out of the gun

i managed to chrono the gun and the compression is perfect, and the entire gearbox is brand new (systema) i just dumped the box in along with the new hop unit.

as i said before, i'll modify the hop unit i have (the old one not the Prometheus) to fit this box.

I'm wondering if the internal dimensions of the DBOYS body are slightly out meaning it needs a taller feed tube on the HOP unit, because the angle of attack that i'm getting the best results supports this hypothesis to a large extent.

thanks for all the responses by the way, everything is appreciated!

[Amos]

Are BB's leaving the mag and entering the chamber?

[doc_pathfinders]

yep, and as i said, when i grip the magazine and pull back (as if it was a second hand-grip) i get a reasonable feed ratio (not perfect but good compared to before)

i'll pick up a dremel to do the modifications to the hop and get back to you all

[Azathoth]

It's possible that:

1) Your magazine springs are really weak and cannot feed.
2) Your magazines just don't like that feed nozzle on your hopup unit.
3) The magazines are not 'properly' seated in your magwell.
4) Your magazine release is causing the issue.

Your problems shouldn't exist with the hopup unit the neo is the best made hopup unit on the market.

What brand magazines are you using? I've run almost everyone brand of mag under the sun in my neo hopup at games when i get tossed spare mags and it always seats properly but many times the mags can't feed due to old springs.

[doc_pathfinders]

ok, after doing a real in-depth analysis of the problem i have come up with the source of the problem, it's two problems that come together seemingly as one,

1. i do have some failiure to feed (magazines are good, and i have tried _many_ ) due to the slightly longer-then-spec distance between the magazine catch and hop unit.

2. the real 'wow' is that when i run this beast on LIPO (11.1V) the air-nozzle ends up blocking the entry for the BB into the HOP chamber (from feed-tube to chamber, where the air-nozzle does it's back-and-forth business) after each shot.

BUT when i run it on an old G&P 9.6V NiMH it works almost flawlessly, (almost, the feeding is a bit off but i'd put it at 5-10% tops) and when i look at the gearbox, i see that the piston is pulled back about 1/3rd of total when using semi on a LIPO and is in the fully-forward(or almost) when using the 9.6.

I WOULD GUESS that the LIPO is causing the gun to cycle too fast, the gearbox is running triple-torque (or more) gears plus magnum motor, and it seems like this setup doesn't like LIPO.

moral of the story, trace the journey of the BB when you have a feeding problem and you'll find the culprit of your problems.

i will still modify my old hop unit to see if that eliminates my feeding problems, and put my Prom chamber in my M4 so it doesn't go to waste.

[doc_pathfinders]

hmmm, well after extensive dremeling it's stillgive me miss-feeds,

i'm going to attach a thin layer of tin-can to the magazine catch to push the magazine up just that last bit..

i would guess it's an incompatibility between the DBOYS body and the SYSTEMA gearbox (opposite ends of the tolerance matrix)

[HKGhost]

If the bbs aren't feeding due to your nozzle moving too fast, install a delay sector clip. That should help unless it's something else.