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Gas piston question

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richk55 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richk55 Quote  Post ReplyReply Direct Link To This Post Topic: Gas piston question
    Posted: Jun 27 2018 at 8:23pm
I was recently given a Universal M1 Carbine ser# 472145.  I took it to the range and it fired OK.  While cleaning it I discovered the gas piston does not move.  I removed the retaining castle nut and the piston does not budge.  All of the Youtube videos I watched about cleaning the rifle always mention that the gas piston should be checked that it moves freely in and out. Was there a change to the design that resulted in a non moving piston or is this a malfunction? 
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blackfish View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jun 27 2018 at 9:20pm
You removed the nut and the gas piston "doesn't move"? Is it stuck in the nut? It should move freely.

But the rifle will function just fine in some cases if it doesn't move freely. That 40K PSI in the chamber can be way more forceful than your fingers can ever be.

My first shot of the M1 Carbine used a carbine with a stuck piston as received from the CMP. After soaking for days in Ed's Red, it was still "stuck" but a live round just blew that sucker out. And it has moved "freely" thereafter. So reassemble and shoot it. THen determine if there's a problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Jun 27 2018 at 10:23pm
Do not fire with nut off!
Do get it moving.
Yes it may work to function by pressure as stated. What concerns me is if the slide does not go fully back and bolts lugs are not in full engagement.

Blackfish is on to something with penatrant.
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richk55 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richk55 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 02 2018 at 6:30pm
I plugged the breach and filled the bore with BP Blaster and let it soak for a day and it did not alleviate the stuck piston but the rifle still fires.  I woud just like to know if Universal made a design change where this is a normal condition or should I stop using the rifle till I get the piston unstuck
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 02 2018 at 6:46pm
Does your gas cylinder look like this?



Or does it look like this?



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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 17 2018 at 1:03pm
He says he removed the castle nut Jack. So I suppose he has a "traditional" GI style piston and retaining nut. I would have thought a SN this far out toward the end of production would have had the "improved" pinned piston....but OP says he has a castle-nut?

I have a 17XXX Universal that has the gas block welded to the barrel, but has the GI style piston and retention system.
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 17 2018 at 1:32pm
Roger, is your SN 17XXX or 17XXXX? I would have expected the OP's SN to be the later welded rectangular type gas block without any castle nut. If yours is 17XXX then I would have expected it to have a GI type gas block. Knowing Universal, I guess anything is possible.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 17 2018 at 3:57pm
Jack....mine IS a 178XX.That' s the reason I hung onto to it as it's GI compatible. However, like many old men my age, we are getting even older and I have other commercial guns. I will go yank this one out of the safe and look at it again and let you know.

EDIT:

Here is a pix. The block is "shaped" somewhat like a GI, but welded in place and uses a stock GI piston and castle nut. I have an IJ 9MM made in 1986 from IJ and Universal parts. The gas block is brazed to the barrel, but it has a floating solid plunger in lieu of the piston and nut.


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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 17 2018 at 5:13pm
Like I said, with Universal you never know. Recently I saw 170XXX Universal with the older USGI style aluminum trigger housing. This SN is well into the "new" design (Gen 2). It looked odd inside of the stock with the larger rectangular cutout. I didn't know what to make of it. Jim M. set me straight.
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richk55 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richk55 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 18 2018 at 8:31am
The gas block on my rifle looks just like the latest picture, GI style shape welded onto the barrel. The mystery to me is how it can fire, eject and reload while the piston is frozen?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 18 2018 at 9:15am
richk55, your mystery on how your carbine can still fire and function was already answered by blackfish.

Originally posted by blackfish blackfish wrote:

It should move freely.
But the rifle will function just fine in some cases if it doesn't move freely. That 40K PSI in the chamber can be way more forceful than your fingers can ever be.


Wayne
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