TM shotgun survey idea

[The Saint]

I don't know if this has been done before, but I thought that with all the TM shotguns being prone to the same problem, maybe there was a human factor in there somewhere. If it can be isolated, one should be able to cut down the odds of their shotty suddenly breaking. Even finding only a necessary cause for the tri-nozzle jam should be somewhat helpful.

In order to do this, I've prepared a list of questions for shotty users. This is the first draft, and I'm looking for input on the relevance of the questions as well as additional questions to add.

TM Shotgun survey

The purpose of this survey is to compare the experiences of TM shotgun users in order to hopefully find behaviours that contribute to the tri-nozzle misfeed problem that seems to crop up all too often and without warning. Please answer the following questions as accurately as possible. Thank you.

1. Which of the following TM shotguns have you owned? (You may include more than one answer)
A. M3 Full Stock
B. M3 Shorty
C. SPAS-12 Full Stock
D. SPAS-12 Stockless
E. M203 Tactical Launcher

2. When did you purchase your weapon(s)?
Month and year:

3. Was your weapon new or used?
A. New
B. Used

4. Have you ever experienced damage to your shotgun’s tri-nozzle as a result of misfeed?
A. Yes
B. Yes, more than once
C. No

5. Do you sling your shotgun?
A. Regularly
B. Sometimes
C. Seldom
D. Never

6. Have you ever performed the one-handed racking on your gun?
A. Once
B. More than once
C. Never

7. How do you treat your gun in the field?
A. Carefully, I do things like:
B. Not too harsh, but not gently either
C. Like it was real steel

8. Do you mis-rack (fail to complete a pump in motion)?
A. Often
B. Sometimes
C. Seldom
D. Never

9. What were the conditions of your shotshells when the tri-nozzle damaged occurred?
A. Brand new
B. Broken in
C. Worn down
D. Unknown/Second hand

10. How do you store your weapon?
A. In its original box
B. In a gun case
C. Lean it against the wall
D. Other, explain:

11. What brand and weight of BBs do you use with your gun?
Brand(s):
Weight(s):

12. How often do you lube your gun?
A. Every chance I get
B. Regularly
C. Seldom
D. Never

13. Do you ever clean your gun?
A. Whenever it’s dirty
B. Once in a while
C. Never

14. Did you ever disassemble your gun before the tri-nozzle damage occurred?
A. Yes
B. No

15. Does your shotgun have any internal upgrades and/or modifications?
A. Yes, it’s got:
B. No

16. Does your shotgun have any external accessories?
A. Yes, it’s got:
B. No

17. Any other information you think might have contributed to your shotgun…
A. Not having tri-nozzle damage, because:
B. Having tri-nozzle damage, because:

18. Where you successful in repairing your tri-nozzle after it was damaged?
A. Yes, by myself
B. Yes, with outside help
C. No

[The Saint]

40 reads and not even "this is a stupid idea" or such? 0_o

[HGI]

saint did you ever play any ultima online free shards????

[The Saint]

Um. Not really. I tried them once, but couldn't really get into it. Er, why?

[Freedom Fighter]

Uhh, having a stock or not on a shotgun does not change the internal feeding mechanism.

[The Saint]

No, but it does change the way stress is placed on the gun during its use.

[aznwillie]

1. B. M3 Shorty
2. Month and year: November 2004
3. A. New
4. A. Yes (damage to tri-nozzle)
5. B. Sometimes (sling)
6. C. Never (one-handed racking)
7. N/A Never been fielded.
8. C. Seldom (mis-rack)
9. A. B. combination of Brand new and Broken in (shot shells)
10. A. In its original box
11. Brand(s): Unfortunately...Crosman, KSC
Weight(s): 0.12, 0.2

12. B. Regularly (lube)
13. B. Once in a while (even when it's not dirty) (cleaning)
14. B. No (disassemble before damage)
15. B. No (internal mods)
16. B. No (external accessories)
17. B. Having tri-nozzle damage, because: shot once in winter
18. B. Yes, with outside help (currently being fixed)

[The Saint]

I should specify that this thread is mainly for fine tuning the list of questions. I'm not actually collecting answers just yet, not until I've made sure that the questions are satisfactory.

aznwillie, thanks for reminding me about weather as a factor.

[TheToastmaster]

That list looks good. You may want to include something about how often it's used and whether indoors or outdoors. [EDIT: and maybe whether it's been rented/loaned out to use too...]


We should have surveys like this for any other chronic problems with other guns that we haven't pinpointed yet, this is an excellent idea. Maybe with something like this, we can get some prevention options up for newbies with guns that have chronic things like this.

[aznwillie]

Yeah, the problem popped up right after/while i was outside during winter.

http://www.airsoftcanada.com/showthr...6&highlight=m3
http://www.infernogmbh.iwarp.com/photo6.html

[MadMax]

I think I have determined the root cause of bb misfeeds. However I haven't gotten around to directly solving it and testing it in the long term so the following is really just conjecture.

I believe that the spring which pushes the tri nozzle body forwards is insufficiently stiff. As wear and related friction develops, the spring is unable to push the nozzle body forward and follow the cocking handle. This allows an extra bb to be loaded which impinges on the tri nozzle when the cocking handle is slammed forward resulting in damage to the tri nozzle.

There are several stages to the cocking cycle:

On the way back:

A cam surface in the loading rods pushes down side pins in a curved loading latch which opens a passage between the shell and the up tube to the breech. Space for 3 bbs opens which becomes preloaded at the beginning of the rearwards cocking half cycle. In the last 1.5" of the rearwards cocking half cycle, the cam surface ends which allows the upwardly sprung loading latch to push upwards. 3 preloaded bbs in the up tube are pushed against the tri nozzle until the cocking rods are pushed a further 1/2" which pushes the tri nozzle back. The retraction of the tri nozzle allows the 3 bbs to be pushed upwards by the upwardly sprung loading latch loading 3 bbs into positions determined by the inside of the breech. This is the end of the rearwards half cycle.

On the way forward:

In the first 1/2" of forward return on the cocking handle, a spring which pushes the tri nozzle forward pushes the nozzle so it follows the ends of the cocking rods. BBs are pushed past a gate in the breech and chambered against the hop up nubbins.

In some cases, the return spring does not exert enough force to push the nozzle forwards. It can get hung in the rearwards position until a surface in the cocking rods rams the nozzle forwards.

At roughly 1.5" of forward travel a cam surface in the cocking rods pulls down the loading latch which opens a passage from the shell into the up tube. Normally, 3 bbs are pushed out of the shotshell (under the shells spring load) until they but against the bottom of the nozzle pushed forwards into the breech.

If the tri nozzle is stuck open, this presents an opportunity to load an extra bb into the breech under the force of the follower spring in the shotshell. When the back stops in the rear of the cocking rods hits the tab in the tri nozzle body, the nozzles are rammed forwards with a fourth bb stuck in the breech. Even if force of pulling the cocking handle forwards doesn't damage the tri nozzles, the slamming force from the mainspring bottoming the tri piston into the back of the tri nozzle body will.


If the tri nozzle return spring is the root cause of the chronic failure of TM shottys, it's a simple job to find a stiffer spring to provide reliable closing of the tri nozzle breech. Somebody go find a spring and try this out. I haven't got my own TM shotty to try this out and I don't have time to do public repair/mods anymore.

[TheToastmaster]

I would consider trying it if mine was working... That sounds about right, since about the only way that makes sense for a bb to get between the 3 ends of the tri-nozzle is for 4 bbs to get in there. With only 3, they naturally go where they're supposed to (until the nozzle is damaged, at which point the first one most often jams). A fourth would rest against all the other three, directly in between the tri-nozzle ends.
Only real problem with that theory is that the nozzle moves back with the racking of the shotgun, not after it so much. I've played with the mechanism with the reciever removed to try to find out info about the problem, and the tri-nozzle may as well be attached to the load bars (the 2 bars that actually transfer the force of racking the shotgun when you do to the pistolbox) from how steadily it moves with the bars...

[MadMax]

The tri nozzle can't be firmly affixed to the cocking bars because it has a total travel of only 1/2" wheras the cocking rods move around 5".

The point of the return spring on the nozzle is to keep the nozzle following the bars in the first 1/2" of forward return so the bbs are fully breeched and opening to the breech closed by the time that the loading latch opens the up tube. If a 4th bb manages to sneak in because the nozzle is stuck open, the nozzle remains jammed open by the extra bb until the gap in the cocking rods ends and forcefully pulls the nozzle forward in the end of the forward stroke.

[TheToastmaster]

Yeah, I know it's not physically attached to it. I just meant that the spring is pretty stiff to begin with. The thing does move pretty solildly.
That does sound right though, that that motion is the problem.
I'm wondering if even just modding it to tighten the space in there up a bit would help. If the tri-nozzle was just a tad longer, so there'd be less space for another bb to get stuck. All that would do to loading, if it was done right, is chamber the bbs a little closer to the hop-ups. Since my nozzle is already broken, I think I'll try that and see if it helps along with trying a simple fill job where the bb gets stuck. I don't have any springs kicking around to try that one, but I may go try to get one soon to try that too.
It'll be hard to tell if any mods that are done to a shotgun work though, since it seems pretty random when bbs actually get jammed and cause the break. It could never happen at all with or without mods, and you'd never know if it stopped the problem, or if you're just lucky... Only if it breaks with a mod done will we be able to rule the mod out.
What a frustrating design flaw.

[MadMax]

Well, I have observed the sticky tri nozzle issue with 3 shotties now. The spring is stiff to begin with. Perhaps over time the nozzle body gets worn and frictiony.

It only takes a stuck nozzle to load extra bbs once. I doesn't have to happen every time.