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Continual Double Feeding TM M14

3831 Views 8 Replies 4 Participants Last post by  Hammar
Currently building a TM 14 DMR with the following parts:

Guarder FTK
SP120 spring
Active breaking programmable Mosfet
Prommy Tight Bore Inner Barrel
Guarder 70 Bucking
H nub

Followed the holy grail guide and have been scanning the net for ages before I started.

When I went to maintain the gearbox I found original internals were getting tired as the gun has had 4 owners prior to me.

Fitted all the new internals, shimmed and checked operation of the gearbox out of the gun - no problems.

Rebuilt the gun with the new hop rubber etc and took it to my local club for setting up the hop.

Found that every time i pulled the trigger 2 bb's come out!!??:nuts:
Adjusted the hop for ages and found the nub was working ok, but still it fired 2 bb's.
Stripped the gun tonight, changed the hop rubber as everyone tells you to do, but still the same.
Have checked the tappet plate for ease of movement and checked the new nozzle is the same length as the old one.
Ive done quite a few type 2 & 3 gearboxes with no problems - I must be missing something???

Had a look at how the inner barrel & hop are arranged in the reciever of the gun and it seems there is only a spring that holds the internal barrel and hop in place - is that right?

Any ideas would be greatly appreciated as I'm itching to climb into my Ghillie for a bit of sneaky airsofting


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Check your ARL and its spring are working properly, if its stuck open that can cause it to feed a bb at either end of the cycle.

Also best to go make an intro post before 1 of the mods gets on your case :yup:
Cheers to the reply,
Checked the ARL, had put a new one in(guarder) and it seems to work ok when you try rotate the gears the wrong way with the motor off.

The gun worked ok prior to my overhaul so feeling a bit of a numpty at the moment! Modified the piston for correct AOE ( one tooth removed)

Looking for things to try ????
The gun worked ok prior to my overhaul so feeling a bit of a numpty at the moment! Modified the piston for correct AOE ( one tooth removed)

Looking for things to try ????
Be aware just cutting a tooth off doesn't correct your AoE, it just prevents pre-engagment when you have corrected your AoE.

If you have corrected your AoE properly, ie. maximum tooth face contact with the piston ate rest, which should happen when the primary teeth of both sector gear and piston are at the 12 oclock position, you should be cutting off all of #1 tooth, most of #2 and half of #3

As for your double feed issue, you say your running a AB MOSFET, try taking the ARL out and then just running it in semi only, the motor sould stop soon enough to prevent a double feed if the AB is working correctly, if you find its not and you can hear the gearbox unwind when you fire a single shot it could be your motor has been fried, which has de-magnetised the magnets reducing there pulling power.

also check your tappet plate and spring are working for the full length of travel and not getting stuck some where along the line.

And as this is a TM derived M14 check your cut-off leaver isn't worn, this will show up like a neon light in the dark when you try the gearbox minus ARL, as the box will just spin on as if nothing has tripped the switch to off, which of coarse is what has actualy happened :yup:
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Thats given me plenty to get on with - thanks.

The AoE was carried out according to the guides, so there was a bit more than just the first tooth removed - about a third of the 2nd tooth required removal, my fault never listed it :nuts:

I put the rifle back together again after a total strip down and it worked for a while then started spitting two again followed by dribbling the bbs out :doh:

Ive got a funny feeling that the ARL is fine for a while then gives up. The new guarder part I fitted didnt seem to have a great spring with it.

Will strip it down again and try what you suggested.

I'm having similiar issues >: instead of double feeding, when the gun is in semi, it shoots full auto most of the time and semi the rest...
Good tips from vindicareassassin.

if that fails.

first thing i would do is to make sure the spring for the tappet-plate is doing okay - try cutting one ring shortening the tappet-plate-spring a bit, this helps to brake the whole gear-set when the motor is moving without power

2nd, if you hold the gun upside down and you put 4 bbs's down the feed-tube in the hopup and shoot the gun upside down without a magazine -does it still double feed? if not then you might wanna consider not loading your magazines fully, a combo of guarders soft rubber (cuz they are soft.. i would try a harder brand, like madbull or similar) and a tired spring for the tappet-plate can cause double-feeds in any gun if the magazine is pushing hard!

if that doesn't work i would start playing around with various nozzle-length's to make sure you actually have an M14 nozzle in it to begin with -you mentioned it had 4 previous owners, and maybe one of them put in a shorter nozzle by mistake? a shorter nozzle could allow 2 bb's to get into the chamber in one stroke.

i strongly doubt this has anything to do with the antireverse-latch as long as it is springing back as it should, if anything keeping it in should reduce double feeding to a minimum since the whole gear-set can´t move in reverse direction, chambering a bb without actually firing it.

have you tried different BB's`? i was getting double-feeds and miss-feeds with Blasters 0.28 in my MP5 and it was totally rebuilt from scratch with all new parts modified to play ball with each other..

food for thought =)
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Great help guys, think ive sorted it.

Not sure if its the guilty components 100% but I found the tappet spring a bit bent out of shape from being fed into its channel over the years. Carefully straightened it out and re-installed it.
Harder rubber bucking installed.
Did your trick Hammar, had the gearbox against the hop upside down etc fired the gun and a single bb came firing out - champion. :shot:
Checked the mosfet is working correctly by stopping the motor - no probs , reprogrammed it to 3 round burst and fired the gun - it fired single then went into 3RB possible contacts or selector issue maybe ?

Ive now swiss cheesed a cardboard box filled with foam with about 300 rounds - cheesy grin time. ( Need to tidy up before my good lady returns :bow:)

Now the questions - Can you get a replacement tappet spring for the M14?

Slightly scunnered (sick) with stripping the M14 to its core but the next time I do what is the best nozzle to fit for long term performance?

Thanks for your help :tup:

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no worries mate! Glad it helped =)

well a new spring shouldnt be too hard to find =) check out or if you want a customersupport that knows english then have a look at for both nozzle and spring

i would avoid the aluminum nozzles since they tend to scratch the inside of the hopupchamber =)

rock on mate
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