Specna Arms Core feeding issues

[nvasilei]

Hi everyone,

New guy here, I've recently bought my first RIF a Specna Arms C07 and have only used it for about 5-6 hours.

It works perfectly with the high cap mag that it came with but when I try different mags (evolution high-cap, battleaxe mid-cap) it has feeding issues.

More specifically it will fire a couple of BBs and then stop firing (pulling the trigger cycles the gun but no BBs come out of the barrel). When I pull the mag out about 4-5 BBs drop out and if I fire again (without a mag in) a single BB comes out the barrel.

Are there any tests I can perform to identify the issue or a fix that I could try?

Thanks!

 

[Colin Allen]

Not all mags and guns are interchangeable.  It is probable that the interface between the tube at the bottom of the hop unit and the magazine is not quite right, preventing the BB latch on the mag being pushed back adequately to allow the BBs to feed.

Have you tried shooting with the mag pushed forward or pulled back?  If it shoots in one of those positions, you can stick sticky backed Velcro (the soft side) in the magwell so that the mag sits correctly.

Some guns are very picky about which mages they will feed from.  Specna are known to be picky; this page may help: https://specnaarms.com/en/magazine-compatibility-chart/

 

[MrTea]

Strange. I used a Specna Arms core-04 with the standard 's-mag' mid caps, Nuprol n-mag mid caps and Battleaxe mid caps and never had an issue. Like Colin said, try holding the mag in a couple of different positions and see what works, you can then either use velcro or even layers of electrical tape on the magazine so it always goes into the position it feeds best in.

 

[Pseudotectonic]

The hop unit should actually be moving forward or backward slightly to locate itself to insert into the feeding port of the mag

Maybe your hop unit is slightly deformed so it is not sliding smoothly, or not inserting itself smoothly into the mag

Can you turn the gun upside down and take a picture of the mag well with strong lighting?

 

[Rogerborg]

The hop unit should actually be moving forward or backward slightly to locate itself to insert into the feeding port of the mag

This is something I've never heard claimed before. I'm not saying that it's wrong, but If there's more than a tiny fraction of a mm of movement then that's begging for feeding or air-seal issues as you change the nozzle-to-bucking distance. Also, plenty of us replace the stock spring in an M4 with o-rings specifically to squish everything together more tightly.

My Specna EDGE is quite fussy, and its mags have different dimensions to most of my other random collection of M4/M16/STANAG mags.

In particular, the distance from the front to the feed tube is a full 1mm larger than (e.g.) my short VN style mags.  Having measured it, I knew that I needed to shim the front of the VN mags with the loop (fabric) side of some self-adhesive velcro tape, which has helped the feeding.

View attachment 83185View attachment 83187

But wait, there's more. Even the BB-stopper inside the magazine feed is different. The VN mag stopper goes further into the feed than the Specna one does, and there's a distinct flat section that protrudes into the feed, thusly.

View attachment 83189

This can lead to the mag not wanting to insert at all as the hop unit feed tube hangs up on top of the magazine stopper, and needs a good wiggle to get it to actually insert.

To ameliorate that, I very carefully filed and sanded the rear of the hop unit feed tube to angle it more. This helps it to slide into the magazine and push the stopper out of the way.

View attachment 83190

The tl;dr version is: don't guess, observe and measure. Calipers and a magnifying glass or jeweller's loupe are better than speculation.

 

[Cannonfodder]

Not all mags and guns are interchangeable.

This. Remember there are different factories for different manufacturers pumping out magazines cheaply so there is always going to be cross compatibility issues.

4 bbs falling out is normal for any AEG and is down to the design of the feed mechanism 

 

[Dan Robinson]

I've marked the mags that work fine with my Specna.   It's not too fussy, but not all this Airsoft are equal. 

Welcome to Airsoft  ?????

 

[Pseudotectonic]

@Rogerborg I got a Specna Edge as well and after tinkering a bit I discovered a few things:

• The inner barrel assembly is free floating inside the outer barrel and can move freely horizontally in the axial direction.
  

• The hop unit is spring loaded on the outer barrel, which pushes it against the gearbox. But when everything is assembled, there is a whole 2 mm of clearance for forward movement, obviously by design for self-locating into magazines. The hop unit feeding tube is chamfered for this purpose (or made more chamfered to improve magazine locating, as you have done).
  

• The inner barrel has surprising amount of wobble inside the outer barrel because it is just free floating inside. All these wobble up and down and side to side, and tilting in any direction, is detrimental for self-location into magazines because when the magazine comes in, there is too much room for error and the hop unit can be outside the correct zone for self-location.
  

• The inner barrel can be shimmed or "stablised" for better accuracy, but this needs to be allowed to move horizontally without friction for the self-location to work.
  

• Similarly the outer barrel can be shimmed on the inside diameter of the upper receiver hole (as opposed to using barrel nut shims to try to hold the barrel in place by sheer friction), to centralise the axis. Besides accuracy, this has added benefit to tightening the guiding slots for the hop unit so there is less chance for the hop unit to rotate axially which again throws off the location of the feeding tube into the magazine.
  

• You can test the forward movement of the hop unit by pushing it forward with fingers through the magwell.
  

View attachment 122597

 

[Pseudotectonic]

PS I think the air seal issues you are talking about are mainly coming from the misalignments of the axis and all the wobbles and misalignments axially between inner barrel vs outer barrel vs upper receiver vs gearbox nozzle.

I think the horizontal movement is by design and not a major cause of air seal issues. I don't know exactly how much extra mm the nozzle goes beyond the hop rubber sealing lip, but I suspect it should have enough mm to cater for this 2 mm movement by design.

It would be all the tilting that makes the nozzle not coaxial and perpendicular with the hop rubber lip causing air seal issues. If it is aligned and coaxial, it shouldn't matter whether the nozzle is inserted by 3 mm or 1 mm, but I am just theorising here.

 

[nvasilei]

Thanks everyone for your answers!

I have checked that my hop up unit can move about 1-2 mm forward if I push on it.

I have tried  holding the mag at different positions and see which works best. It seems that I get less jams (after 10-15 BBs instead of 2-3) when the mag is fully pushed forward. I've wrapped the mag with electrical tape so that it sits more snug inside the magwell.

Also when the RIF stops firing shaking it a little seems to unjam it every time (with or without tape on the mag).

Comparing the battleaxe mid-cap (which is not feeding properly) and my specna arms high cap it seems that the feed tube on the battleaxe mag sits about 1 mm proud. Does it make sense to file it down and get them to match?

Also just to mention that I have tried some of the mags that misfeed in my RIF on my friend's RIF (same model, we actually ordered them together) and they seem to work fine (at least for much longer that mine) but could be due to different tolerances between the two .

I will have to check all the mags that I have problems with on his RIF to make sure.

I've also attached a picture of the magwell maybe you can spot something wrong with it and the two mags in question (on left is the battleaxe one and on the right is specna arms).

Thanks again!

View attachment 122616

View attachment 122620

View attachment 122621

 

[nvasilei]

@Dan Robinson Do you have a list of mags that work with your Specna that you could share? Which model do you have?

Thanks for the warm welcme ???

 

[Dan Robinson]

@Dan Robinson Do you have a list of mags that work with your Specna that you could share? Which model do you have?

Thanks for the warm welcme ???

Two of the three I have here are ICS and another is Nuprol.  I think the other one is Kings Arms?  Could be wrong on that though.   Don't tell my boy about the ICS ones though - one will be his 

  

 

[Rogerborg]

Thanks for the warm welcme ???

Oh, ahoy and welcome and all that. You've very nearly got a good slap-fight going here about hop unit springs, that's a good start.  

 

[nvasilei]

@Dan Robinson Thanks for the info! Not a word about the ICS ?