Bb curve

[Pollynator_bravo2]

Evening all

ive found that my bbs are curving right. What could cause this please ?

 

[RostokMcSpoons]

I've had this, it was a torn hop rubber, a flap of rubber was impinging on the bore and causing a second hop effect.

Otherwise, it could be a misaligned barrel / hop unit, though I think that's unlikely given the way the barrels I've seen are put together.

 

[Colin Allen]

Is it a new gun? Has this just started happening?

Possibilities include:

The barrel being slightly twisted in the hop unit.  The bump in the rubber should be at the top dead centre position, not slightly off to one side.

The hop nub being slightly off centre or misshapen.

The inner barrel not being utterly straight; take it out and roll it on a flat surface to check.

The inner barrel being dirty.

Your gun being an StG 44 with a Krummlauf.

 

[Pollynator_bravo2]

Ok cheers for this. I think it’s the nub position most probably. It had a half job done on it which I’ve just discovered. It looks like an omega nub is in but not a maple bucking

 

[EDcase]

Would be worth cleaning the barrel as a first option

 

[alxndrhll]

I'd argue the first thing to ensure is that you're holding your RIF straight. Not intended to sound condescending at all, just genuinely worth checking. Everything else listed are potential candidates, but it could be as simple as your RIF isn't being held plumb. I've seen it more times than I can count, and I've absolutely been guilty of it myself. Especially on a RIF I'm not familiar with/have put a different stock on to usual.

 

[Tactical Pith Helmet]

I had this on a PPSh.  The BBs were clipping the outer barrel.  If you shoot a few into a bucket of water you can see if they've deformed/chipped by clipping something.

It's an easy way to eliminate something at least.  

 

[Pollynator_bravo2]

It’s weird as it’s worse on single fire than on three round burst or binary ?‍This tech stuff is a lesson every day lol

 

[Sneaky]

Take it apart, clean, inspect, then try again.

 

[Rogerborg]

Mmm, the tiniest amount of barrel rotation can cause this, and the keying provided by the c-clip is only approximate. It's a wonder that more guns don't suffer from it.

 

[Fatboy40]

I've had plenty of trouble with ML Omega nubs not being centered 100% correctly, even slightly off gives a left or right curve that becomes more pronounced when shooting at distance (I need to tweaks my son's RIF again before we next play due to this).

I went the nuclear option to say goodbye to this forever, with a Maxx Model M4A-PRO hop unit and the solid metal nub which acts like a TDC.

 

[Adolf Hamster]

I've had plenty of trouble with ML Omega nubs not being centered 100% correctly, even slightly off gives a left or right curve that becomes more pronounced when shooting at distance (I need to tweaks my son's RIF again before we next play due to this).

Aye the ml buckings are super sensitive to being setup properly square, worth it though.

I find the non-maple leaf nubs can be off-square although the proper ones are generally pretty good.

Ofc that only helps when the hop unit/arm is capable of holding the nub and barrel square in the first place.

 

[Colin Allen]

Ofc that only helps when the hop unit/arm is capable of holding the nub and barrel square in the first place.

That brings back suppressed memories of a King Arms SVD. ?

 

[Oneshotscott]

All members above are spot on. 

I fitted a new zci barrel, ML hop and omega nub to a brand new g&g sr15 e3 mod2 (which was in hindsight really didn't need upgrading). 

The omega was an absolute nightmare to set up.   But once it seated just how I wanted it to the bb's are not like lasers as that's impossible, but they're no longer swerving like a 10 bob flyaway football. 

 

[Pollynator_bravo2]

I've had plenty of trouble with ML Omega nubs not being centered 100% correctly, even slightly off gives a left or right curve that becomes more pronounced when shooting at distance (I need to tweaks my son's RIF again before we next play due to this).

I went the nuclear option to say goodbye to this forever, with a Maxx Model M4A-PRO hop unit and the solid metal nub which acts like a TDC.

That hop sounds like a good option. Where can I get one?

Mmm, the tiniest amount of barrel rotation can cause this, and the keying provided by the c-clip is only approximate. It's a wonder that more guns don't suffer from it.

I’ve noticed that the barrel can move a lot with the clip attached

Take it apart, clean, inspect, then try again.

I did this. Unfortunately the fps then dropped from 280 to 80 ?‍  This build has been a nightmare. I then took off the old bucking and the nub and fitted another omega which was slightly shorter than the original omega I fitted ??and I also fitted a ML bucking. The fps went up to 120-130. I’m now thinking it’s hop/barrel related so I’ve removed the big tension spring and fitted some O rings to push the hop firmer into the gear box. I’m yet to test it but it’s something new to try. I know the gear box and associated air compression components are good as that was my last area of attack. 
I have 13:1 gears fitted but an 18k infinity motor. I don’t know if that will give me problems. I’m running a m105 spring but I’ve never been above 280 fps

 

[Adolf Hamster]

I’ve noticed that the barrel can move a lot with the clip attached

Very common that, the upside is at least you can twiddle it to adjust the rotation looking down the barrel by eye.

The fps went up to 120-130. I’m now thinking it’s hop/barrel related so I’ve removed the big tension spring and fitted some O rings to push the hop firmer into the gear box

It is common to get leaks if the hop is sitting forward, or the nozzle is too short/has damage on the tip.

One thing to check is looking up the feed tube is if the feedlips are visible, usually you're looking for too much protrusion as a cause of feeding issues but if there's too little then the feed lips are too short (admittedly unlikely for a ml bucking) or the barrel is sitting forward which can happen depending on where the cuts for the c clip line up with the c clip and the hop.

have 13:1 gears fitted but an 18k infinity motor. I don’t know if that will give me problems.

If you're on 7.4v then that doesnt sound likely, although on 11.1 you might be nearing that territory.

Light pme tends to manifest as a drop in fps on auto but not semi so probably not the issue here.

 

[Pollynator_bravo2]

I can just about see the bucking so probs sort slidin the barrel down a few mm

 

[Adolf Hamster]

I can just about see the bucking so probs sort slidin the barrel down a few mm

about ~0.5mm protruding through isn't a problem for airseal moreso if you couldn't see it at all.

more protrusion is better for air seal but at a certain point will make the mag's job a lot harder, if your gun's feeding on the mags you have then don't worry about it.

 

[Pollynator_bravo2]

Cracked it in the end. Nub was positioned wrong some how. Sorted it and that was then back to normal

 

[Rogerborg]

Nub was positioned wrong some how

Thanks for the followup, it's good to hear that you got it solved.  I don't like Omega nubs for this reason, they seem quite prone to it.