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Blish Broke Again


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last time I shot it the blish broke.. tonight I took the gun apart and there it is broke again.

 

I swapped out bolts. not sure what else to swap out? somethings going on. last time you guys thought old or a defect. its something else

 

advice? I oil the bolt and blish pretty well. the guns action is like glass its so smooth. no friction anywhere

 

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Edited by huggytree
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I have never known an H-lock to break and you have broken two. Wow.

Have you tried a different actuator? Because where the lock is broken is where

it interlocks with the actuator. My guess is there is un-even force being put on the

H-lock causing it to fatigue and break.

 

Bob

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more pics..the 2 shiny spots. the impact in the middle is pronounced and this was a mint blish. I see wear on 3 sides of the center of this. there is some wear on this one side

 

reconbob- ill swap actuators.

 

 

 

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Edited by huggytree
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1940 S1928

S&B ammo

Original S marked parts

 

ive shot thousands of rounds out of this gun...

 

heres pics of the actuator

 

So now i have swapped the actuator and bolt. both are minty/nos condition now...blish is also nos looking...the action is not as loose anymore...still glass, but with a bit of extra friction..takes a bit more force to pull the bolt back..bit tighter feeling

 

for those who have teased me about having full parts kits for all my guns and lots of multiples? nights like tonight is why. sure is nice to open a box full of parts, grab some nice NOS parts. bought another spare blish already off GB :) I might have to start buying blish locks in bulk!!

 

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M8SpHj6.jpg

Edited by huggytree
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APEX has a selection of nice Blish locks on hand:

https://www.apexgunparts.com/thompson-1928a1-blish-lock-g.html

We also have 1928A1 bolts and actuators (several choices of each)

https://www.apexgunparts.com/machine-guns/sub-machine-guns/thompson-45-acp.html

I too am a big believer in having spares along on a trip to the range!
We hear the tales of ruined trips all the time.

Richard

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Having the parts on hand - great idea.

 

But lets get back to the problem. What was the root cause? Can you look at the fracture surface (maybe with 10x or greater magnification) and see if it was indeed a brittle fracture of some sort of fatigue fracture? I do doubt it was fatigue as you said this time it was a new lock. A brittle fracture surface looks like a rocky, a fatigue fracture surface looks like waves on a beach. Google it.

 

Assuming it is a brittle fracture, it means somehow you overloaded the lock. The loads being S&B not hand reloads are probably not the issue. So the geometry becomes suspect. Have you taken a real close look at either the bolt and the receiver lock rail surfaces? Maybe there is something there that is causing the mechanism to stop in operation. Like a chunk of metal galled (spalled) up somewhere. I would be suspect of all of the internals, since it is a WWII gun I would not be as suspect of the gun itself. But it does deserve a closer look.

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Follow Giant Panda's advice and look for any nicks or burrs in the lock slots in the receiver, the bolt or the actuator. If there are any, carefully stone them out but do not break any sharp edges.

 

If no burrs are present, I would just about bet the farm that the problem is a tight spot in the blish slot in the actuator. When the gun is fired, the rearward motion of the bolt forces the lock to move in the receiver slots. If there was a problem with either bolt or receiver, the actuator would not see any effect, it would be more or less along for the ride. But if the lock slides freely in the bolt and receiver and sticks in the actuator then the actuator will see all the load.


Put some layout blue on the faces of the slot, re-assemble the upper and work the action by hand by moving the bolt not the actuator the blue will wear off the high spots.

Edited by StrangeRanger
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the blish marks you have more than likely came from firing when broken, one breaking possible but two? either its getting pinched during cycling, it may feel slick cycling by hand but when cycling by hand the actuator is cycling the action back, when firing its the bolt cycling, different contact points, one thing you could try is with the bolt forward use a piece of wooden dowel and insert it in the barrel then push and it will unlock the action and cycle the blot back, see if there is a tight spot.

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Could there be an issue with "super-lubrication" on something that actually relies on a little "friction"? Using an oil that is TOO slippery?

 

Engine oils are rated on lubricity. Trans fluid, for example, needs to allow clutches to acquire friction to transmit torque. Two radically different products.....Phil

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I'm holding one of my used Savage Blish locks in my hand now, it has no similar wear marks on the side proof "S" on that corner. Makes me think something is binding it up in the rail causing that, or the wear came after it broke in the center. Really, perhaps a measurement of the inside rail front to back with a micrometer might shed some light on what is binding. The impact mark in the center from the actuator and bolt contact should be even across it, leaving the side wear as unusual.

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Interesting failure. In live fire the bolt pushes the lock which pushes to actuator to the rear. This is a bit different then pulling the actuator. I would remove the recoil spring and pilot. Then try sliding the bolt back and forth by the pushing bolt to the rear instead of pulling the actuator. There must be some binding to fracture 2 different locks. Edited by timkel
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like I said with the bolt forward use a wooden length of dowel down the barrel and push it against a hard surface, see if there is a tight or rough spot when the bolt moves from the locked position, this is how we checked the action in the good old days when we could shoot in Canada

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