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Is my Thompson experiencing cartridge ignition while the bolt is open?


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#1 imageaudio

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Posted 26 September 2019 - 01:57 PM

Just took my Thompson to the range for the first time (indoor as the gun is currently in prison at my local FFL until I receive my stamp)

 

We recorded the gun firing with our phone camera (so nothing high tech) but I was concerned when watching the video.   When examining the video, there appears to be burning propellent at both the muzzle and the ejection port at the same time.     I'd post the video if that's possible but don't know how to do that.   I have grabbed a few video frames which I think demonstrates what I'm describing.

 

Is this something that should be of concern to me?    Perhaps it's just a slow burning powder?   Or maybe it's just an indoor range in a low light situation so the "fire" effect is much more pronounced, especially as viewed against a black wall?    But to some extent, I must be loosing power and it does concern me that explosions are happening at the Ejection port of my firearm with the bolt retracting.     Or is this the way all Thompson's function?

 

I already own a STEN and an MP40 and don't see this type of effect when shooting them.   Of course, they are 9mm and now I'm shooting 45.

 

Thanks in advance for any/all input.

 

 

 

Attached Files


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#2 Kilroy

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Posted 26 September 2019 - 02:07 PM

Interested to see what others say, but I can say that my M1928A1 does it too.
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#3 ppgcowboy

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Posted 26 September 2019 - 02:20 PM

What you are seeing is that the gases are still burning.
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#4 mohawk64

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Posted 26 September 2019 - 02:48 PM

Mine does it
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#5 StrangeRanger

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Posted 26 September 2019 - 03:14 PM

It's not firing out of battery, what you are seeing is occurring after the round has fired with the gun in battery and the blowback has moved the bolt rearwards on the recoil stroke.  The absolutely dirtiest area of my Thompson M1 after a trip to the range is the feed ramp section between the front of the mag well and the back of the chamber.  It is covered in burnt powder residue.  The best explanation for that is exactly what you are seeing.  At the risk of sounding like a used car salesman "they all do that."  FWIW my former WH28 didn't get nearly as dirty in this area.  Perhaps the Blish lock slowed things down just enough.


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#6 gijive

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Posted 26 September 2019 - 03:18 PM

What you are seeing is that the gases are still burning.

Yes, ppgcowboy is correct.  All Thompsons demonstrate that phenomenon on an indoor range.  It just isn't as noticeable in daylight at outdoor ranges.  I would guess the visibility of the burning powder remnants also depends on the powder mixture in the ammunition used.

 

Here is a video of my son shooting a Colt's 1921 Model Thompson at an indoor police range.

 

Attached File  TSMG Model of 1921-# 4755(1).mov   49.05MB   110 downloads


Edited by gijive, 26 September 2019 - 03:31 PM.

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#7 imageaudio

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Posted 26 September 2019 - 04:41 PM

Thanks Gentlemen for your prompt replies.     Makes me feel a little more confident.   I knew it was a straight blowback but "inquiring minds want to know!"    These where reloads as I had some S&B on order but had not arrived yet.    Was thinking that perhaps my recoil spring was a little light or possibly some other issue.    Glad to know this is not considered an issue by others more experienced with the Thompson. 

 

Once I get some mil spec ammo on hand, I'll try to convince my FFL to go to the range with me again (cost's me 2 range fees and about 3 mags of ammo for him to shoot).   I'll report back if I see anything different.


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#8 BillyDixon

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Posted 26 September 2019 - 05:50 PM

ive seen this depending on what powder used in reloades, some ammo durtier than others, try a video of the ejection port area while firing at night, just sayn


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#9 Grasshopper

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Posted 26 September 2019 - 10:08 PM

Hi imageaudio,

 

This is common to most SMG's.  If you get a chance attend a well organized night shoot; flames/burning powder is evident from both the ejection port and muzzle.  Autoloading firearms also have burning powder in the ejected casings while on their way to the ground.  Modern cameras with 250-1000 frames per second catch the burning powder.

 

Enjoy,

 

Grasshopper


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#10 DINK

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Posted 27 September 2019 - 06:22 AM

Put a new recoil spring in it anyway.  Maybe the current one is fine, maybe it isn't, but a new spring is very cheap insurance.


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#11 imageaudio

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Posted 10 October 2019 - 12:01 AM

Update from the range.

Used S&B which felt a lot hotter than my reloads and not nearly as much fire in the ejection port area. Tried my reloads again and the fire at the muzzle as well as the ejection port lit up the range again. Guessing the fireworks effect is a result of a slower burning powder.

Used 230 grain Bullets in all the tests. Also swapped out recoil spring. Same results. S&B was the hotter load but less flame effect.

Conclusions: if I want to impress my friends on the next 4th of July, Im going to take them to the range and let them shoot my reloads. Way more exciting than m80s or bottle rockets!
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#12 Junkhunter

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Posted 10 October 2019 - 09:01 PM

I am working thru 230 Gr WW231 reloads they produce a fair amount of burning powder at the port. Occasionally a hot flake on my arm.
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