!!!HELP!!! Rubber, hop, barrel, nozzle compatibilty issues!!!

[inhen]

Madbull Ultimate Hop + Element H Nub + black Shark rubber + Element 6.04 x 248mm barrel + Ultimate airseal nozzle = vicious rof + adequate accuracy at 30yrd

 

However!

 

Madbull Ultimate Hop + Element H Nub + Prometheus Delta strike blue Rubber + Prometheus Delta Strike 6.2 x 275.5mm barrel + Ultimate airseal nozzle = viciously vicious rof however only occasionally actually firing and mostly shattered bb fragments.

 

The bbs seem to be getting stuck in the hop and they are being broken by the nozzle. Its easy to push a bb through the collar of the hop rubber when the gun is disassembled but the nozzle cannot when the gun is assembled.

 

This is getting frustrating now as its a parts gun, 6 months in the making and its so close to realisation.

[RR01]

Sounds like you've got a problem with the inner barrel. 6.02 is a bit tight for an AEG barrel, as there is very little leeway in the internal diameter if there is the slightest problem with BBs. I had a problem recently on my spring SVD that has a 6.01 inner barrel and that was getting BBs jambed in it as well (admittedly quite old 0.3 bio ammo). The guys at Redwolf don't recommend going tighter than 6.03 in an AEG.

[Samurai]

Sometimes the rubber's mouth protrudes into the BB's way as it gets feeded from the vertical part of the hopup unit, and on high rof it can get caught between the barrel and the BB. Use a rubber that doesn't protrude that much.

[inhen]

Its not a 6.02 it's a 6.2mm very loose, highly polished, Delta Strike type nub aperture.

 

I'm going to cut the shark rubber to fit the barrel, it's much softer with a smaller collar.

 

So how does the angle of the rubber affect the bb as it's pushed in to the hop chamber?

[RR01]

Sorry, thought your size was a typo. If it's 6.2 then that may be your problem, as the BBs may be getting pushed off centre because of all that extra room in there. Personally, if the 6.04 was doing a good job I'd put it back in and forget the 6.2 inner.

[inhen]

Tbh I think even the 6.04 was too tight, I would occasionally get bbs stacking up in the barrel during full auto firing and when burst firing the first bb would fly straight and true but the second would drop low left and the third would fly straight. Plus 25yrds range is useless.

 

The idea behind the 6.2mm barrel is to create flow around the bb to guide it down the barrel rather than force it down on a cushion as with tight bore barrels. The chamber that fits on the end of the Prometheus barrel has 3 nubs at the bottom and the hop nub protruding from the top to centralise the bb in the barrel. When I've loaded bbs manually the result has been spectacular to say the very least! Range is vastly improved to the point that my garden is no longer long enough to see when the bb's trajectory is overcome by the top spin. Accuracy is 100% (so far) at 25yrds with gun clamped in a vice, 1.5" groups!

 

So I don't think its the barrel, I can't emphasise enough how impressed I am with its performance. Something is stopping the bb before it gets past the rubber collar. Is it the angle of the rubber? Where is the angle of the rubber measured from?

[Liam Porter]

It may be the collar of the rubber. I have a Prometheus red rubber which I've tried to use in sniper rifle and AEG, and it simply doesn't work.

 

In my AEG, it doesn't feed, and the nozzle/tappet plate isn't strong enough to force the BB through.

 

In the sniper though, it's fed by the force of me pushing the bolt forwards, so if I apply enough force, it will feed.

The issue is, when I do this, the nozzle either dents the BBs loads, making them jam or fire extremely inaccurately, or it shatters the BB and leaves fragments in the barrel.

 

I've just stopped using Prometheus rubbers and stick to the MadBull blue ones. If you cut a bit of the collar/lip off and make it so that when you have just the barrel and hop rubber (out the gun), you can easily roll a BB through, then it should work, but I've not tried that, just what I've read of other people doing.

[inhen]

Good stuff, you would have thought that the tappet plate spring would be strong enough to feed the bb but obviously not. Glad someone else has had the same issue. The barrel came with the blue/soft rubber so god knows how bad the red would be. I've even got an uprated spring set in the gearbox.

[Ian_Gere]

Be careful you don't cut too much off the rubber's collar or you'll lose compression.

 

Personally I would go with a Prometheus Soft (Purple) rubber and an H-nub.

 

I dunno what kind of hamster droppings the people at Redwolf are firing through AEG's, but I've got a 6.02mm Chromed Brass barrel in my AKS-74U (which I put back in after comparing with a Systema BS 6.04mm). I've also got a PDI 6.01mm in my Vz61 Skorpion. No problems. No jams. No alleged bizarre effects believed to be possible due to an incomplete understanding of the entire system, rather just a part of it, and thereafter spotted 'for real' to be featured in sworn testimony on t'internet.

 

I generally use Blaster 0.25 in the former, 0.2 in the latter, but I have fired maybe 15 thousand BB King 0.2's through the former and a few hundred of them through the latter.

 

I'll be interested to find out how your AEG performs with the 6.2 barrel in the field, inhen, assuming you do get it working. I have to say that I'm sceptical, but obviously I'd like to be proved wrong. Just checking: you do have a tappet plate delayer clip/chip on your sector gear in this build, right?

[inhen]

I'll be interested to find out how your AEG performs with the 6.2 barrel in the field, inhen, assuming you do get it working. I have to say that I'm sceptical, but obviously I'd like to be proved wrong. Just checking: you do have a tappet plate delayer clip/chip on your sector gear in this build, right?

There is a delayer on the sector gear but its a small baring rather than a chip. I'I've hdd some encouraging results today using modified shark rubber and thread locking the barrel in place in the hop unit. Firing through the inner barrel when not installed in the outer provides fantastically consistent results, however when the whole gun is assembled I sometimes get 1 BB per 2 pulls of the trigger. Occasionally BBs roll out of the barrel and in full auto I have noticed that sometimes when burst firing one third of BBs fly straight for 30+ yards another third spin high and left at 20yrds and a third drop left.

 

She is 40 - 50% consistent over the last 1000 BBs I have managed to fire, so a big improvement on a few shattered fragments!

[Ian_Gere]

What concerns me about the wide bore theory is that it does nothing to the air itself to make it resist a BB moving off centre within the barrel. The BB may start in the centre, due to hop fins or whatever, but vibration from firing and involuntary body movement, not to mention deliberate movement like running, or even shifting aim during full-auto fire, must surely move the barrel around the BB once fired, which then puts more air on 1 side of the BB and, as polished as the inner surface may be it has a higher friction coefficient than air, so the axis of hop induced backspin must be affected: any deviation from exactly perpendicular to the trajectory induces yaw and also reduces range, since it makes the force generated less effective as lift if it is not acting exactly opposite to gravity.

 

I suspect that movement could cause a BB to 'stick' to one portion of a wider barrel, due to the extra air on the opposite side, but if that is not the case, we are being asked to believe that the same effect could overcome one glaring fact: that the wider the barrel, the wider the exit cone of potential trajectories a BB could be on at the moment it leaves the muzzle. Clamped to a bench, yeah I can believe it; in the hands of a person skirmishing - bollocks!

[inhen]

I'm starting to agree with you Ian, I don't know how long these loose bore barrels ha e been around but I can't find much in the way of reference material on testing and results, even on Airsoft Mechanics. As you point out the barrel's performance on the bench doesnt necessarily suggest results that could be replicated in the field. But I am willing to keep investigating and trying any suggestions, I have been given a thesis on ballistics to read so I may be gone sometime!

 

Anyway I'm starting to think that the gearbox may be part of the issue as the resting place of the gear and there fore the nozzle allows for the next BB in the hop to sit in such a way that when the nozzle moves forward it is pushed up and mis feeds/folds the upper edge of the hop rubber in trapping the BB. So I'll try a range of products I've found specifically for the barrel and probably strip the gearbox again to make sure I haven't missed anything obvious!

[Ian_Gere]

Sounds like the rubber may be sitting too far off the barrel perhaps. That said, you wouldn't be the 1st person to have issues with the collar of shark hop rubbers, eh Ed?

[inhen]

Eureka!

 

I have identified the problem (fingers crossed!) It's the cylinder head nozzle, its split right down the middle and its chewing up and misaligning the air seal nozzle. I noticed black shavings in the barrel when i cleaned it.

 

Now that I'm looking closer I have also noted that the cylinder isn't sitting square in the gearbox.

 

Can anyone recommend a cnc machined, reinforced 9mm v2 box? Preferably with a quick change spring guide.

[Ian_Gere]

These are supposed to be the shit.

[inhen]

They do indeed appear to be 'the shit'.

 

But not reinforced.

[Ian_Gere]

Possibly being made from 7075 and CNC finished means they don't need to be specifically reinforced...?

[inhen]

Fair point!

 

I swapped out the Prometheus barrel for the crappy Element 6.04 and changed the cylinder head and nozzle, re shimmed and re built the gearbox and canged the black shark rubber for the clear and BOOM!

[inhen]

Not exactly the most scientific approach to the problem but the results speak for themselves!

 

I've fired 1200 BBs now without a single jam or double feed! Yay!

 

I can hit a shoe box 120 times in 3.7seconds at 25yrds!

 

Me thinks the feed system is working rather well for now, I'm almost put off changing the barrel back when the Prometheus bits arrive but if I can achieve results like this with a £20 barrel just imagine...

[Ian_Gere]

Element stuff may be cheap but it's not crap.

[jcheeseright]

yeah, if you're getting decent performance now (sounds like you are!) why spend money to potentially bugger it up?

 

If it aint broke... don't fix it!

[Mr Monkey Nuts]

Just imagine what? How over rated promethius stuff is?

[inhen]

 

Just imagine what? How over rated promethius stuff is?

Well I'm going to reserve judgement until I've tried the Prometheus barrel with the right rubber and nub. This is my first build so its a learning curve. I don't know what results to expect, I don't even know what range an aeg should be effective to. I haven't even started experimenting with ammo yet either, it's all so exciting!

 

So where does PDI come on the quality curve? I've ordered a 6.05 barrel, looks pretty standard, no fancy hop chamber, just machined from one peice.

 

The problem I've got now is she won't fire full auto! Just stopped halfway through a mag.

[Samurai]

PDI is on the top.