TM P90 feed issue - nozzle not reliably retracting

[Solomance]

This is my old reliable, well was. This is a 10+ year old TM P90. It's spent a year and a half in its case. I got posted and have been out of the loop for a while.

I'v rebuilt my p90 mech box 3 times now. Still getting feed issues. Seems like the nozzle just isn't moving far enough back to reliably let a bb feed.

Replaced nozzle and tappet plate with brand new versions of what was originally in there. cleaned and re-greased everything.

Registration of the mechbox and inner barrel looks good. Manually feeding bbs in by hand same feed results as with a mag in. Thinking of either shaving the nozzle to be shorter or modifying the tappet plate to pull back farther.

Oh hop assembly looks fine no damage there.

Issue persists.

What have I missed or what am I forgetting?

The good : air seal is still solid and when it shoots its shooting 370 fps with the beefy spring after being cased for so long.

Thanks in advance for any advice or suggestions.

[Spike]

Try a sector delay chip
http://www.airsoftstore.ca/index.php...products_id=12
They seem to solve most nozzle related feeding problems.

It's also possible that you got a mislabelled nozzle... do you have a pair of calipers to measure how long your nozzle is?

[Solomance]

Dont have a pair of calipers kicking around, but will try that delay part and see if it helps.

Thanks dude. Will post back once parts are in.

[ThunderCactus]

When you assemble the mechbox and you push on the nozzle, does it move back and forth freely, or does it get stuck?
Could be the sector gear is pinching it

[lurkingknight]

did you change anything recently on your rebuild?

If you changed out tappet plate, hop up rubber or nozzle, you'll need to look at those parts a little more closely.

Compare the nozzles side by side if you replaced it but don't have calipers to measure. As little as a tenth of a mm is enough to fuck it up. Are the profiles of the nozzle tip the same? are they both beveled at the same angle?

[Solomance]

Originally Posted by ThunderCactus

When you assemble the mechbox and you push on the nozzle, does it move back and forth freely, or does it get stuck?
Could be the sector gear is pinching it

Moves freely with out snags.

Originally Posted by lurkingknight

did you change anything recently on your rebuild?

If you changed out tappet plate, hop up rubber or nozzle, you'll need to look at those parts a little more closely.

Compare the nozzles side by side if you replaced it but don't have calipers to measure. As little as a tenth of a mm is enough to fuck it up. Are the profiles of the nozzle tip the same? are they both beveled at the same angle?

Tappet and nozzle were changes to brand new versions of the same parts that were previously installed. Always order spares to keep on hand.

Nozzles appear identical as far as tip profile.

I have the delat clip and some more nozzles on the way. Should be in before the weekend. Will update.

[Short Round]

I did the same thing you did Solomance (replace the nozzle and tappet plate) to my P90 a while ago, except I also replaced the motor for a Lonex A1 Titan. Still ran into the same issues.

I found that when I use my Echo1 magazines (fully filled) which have a weaker spring in them they feed fine, however when I use my Tokyo Marui magazines (fully filled) which are newer and have a stronger spring, I run into feeding issues until the 10th-20th shot.

Here is hoping the Sector Clips will solve your problem.

[lurkingknight]

for a year and a half to 2 years I had no feeding issues then all of the sudden my p90 started not shooting out of fully loaded MAG midcaps when they used to just fine. Mostly low fps shots every 2 or 3 shots at the start and after about half way it resumes normal function. It seems the p90 is really weird when it comes to temperamental feeding issues.

I would not rule out tappet plate spring either. There's no aftermarket replacement for them. (for shortround's issue)

[Solomance]

Best replacement for the tappet spring is a spring from a bic lighter. Can also be used for the trigger return sprin in the mech box with some cutting and bending.

[lurkingknight]

I don't think a bic lighter spring is going to replace the tappet spring.

It's a 1.5inch compression spring with about 2-3 pounds per inch compression, maybe more since I can't measure the rate on it without a spring dyno.

I've only read about the bic lighter spring replacing the main trigger block spring or was it the semi trigger shuttle spring? those are expansion springs though.

[Solomance]

Issue resolved!

Got my parts in last night. Tore down the mech box and installed the delay clip: issue remained. Cracked it open again and swapped the nozzle with one just slightly shorter. An AK nozzle infact and now every shot is feeding and no FPS loss.

Left the delay clip in as I was too lazy to do another tear down to get it out :P

So parts used:
SHS AK Nozzle with O-ring - Long
http://www.airsoftstore.ca/index.php...products_id=32

Lonex Sector Gear Delay Clip
http://www.airsoftstore.ca/index.php...products_id=12


Thanks once again for the suggestions.

[pestobanana]

The issue for lurkingknight is nozzle misalignment.

[lurkingknight]

but it's not.. there's no play in the nozzle on the cylinder head. Even with new parts.

[pestobanana]

Originally Posted by lurkingknight

but it's not.. there's no play in the nozzle on the cylinder head. Even with new parts.

Have you tried a hop up rubber with thinner lips and enhancing the taper on your nozzle?

[lurkingknight]

I replaced the hop rubber, same effect. tried softer rubber, no change. Tried different brand of rubber, also no change. Reverted to a stock barrel with stock rubber using the m-nub, also no change. Replaced the nozzle and cylinder heads with brand new versions of what was working before, no change. The gun just stopped feed/shooting correctly at some point and refuses to shoot full mags.

If the angle of the nozzle worked when new, but was worn to the point where it would impede feeding, a new one should have fixed it (logically) Same with any chance the cylinder head and nozzle relationship also wore to the point of changing the feeding characteristic.

The only other possibility is tappet plate return is being interfered with with a full mag. I observed a similar behavior on my g36 when the tappet hit the trigger shuttle return spring on it's way to battery, there was evidence of this when I opened up the gearbox and discovered the shuttle spring was mangled.

The problem here is that the v6 spring is a compression spring, and the tappet itself is isolated completely so it can't hit anything during the cycle, so my only working theory is that the tappet spring is weakened such that the force of a full mag is causing enough drag to slow the tappet down during the return to battery position. Because there's no definitive replacement spring for a v6 tappet spring, and I don't have a method of measuring the spring rate, I can't be sure I can find a proper replacement, though I have found some with similar dimensions but varied rates from 4 pounds per inch to 16 pounds per inch.