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Old 06-26-2011, 10:29 PM
terrapin88 terrapin88 is offline
 
Join Date: Mar 2010
Location: Massachusetts
Posts: 6
Default Piston came off op rod. Repair or replace rod?

At the range today zeroing my M1 after years of it sleeping in the back of my safe. I made it thru 3 clips without issue (good grouping too ). I pop in clip 4 and after 1st round fires, my bolt jams back into the receiver heel, and the oprod just feels funny. Get it home and begin to strip the rifle and as I pull out the gas plug (new style with poppet) the piston comes off stuck to the back of the plug. It took some serious effort to unscrew the plug at first. That's never been the norm with this rifle.

So, looks like the piston broke off clean from the rod where the solder joint is, or was. I found no other damage to the rod, bolt, or any other parts. I was using reloads that I made when this happened.

Specs on my reloads.--> 47.4g (+/- 1g on average weighing every 5th) of IMR 4895 in 2x fired commercial brass, 150g speer soft point BT's, and WLR primers.
I settled on this load ~8 years ago and have been using it since with great results. The only wild card is the speer 150 soft points. I normally use milsurp 150g FMJ's projectiles. Something else to mention is the powder has to be 4 years old, but tightly sealed in it's container.

After the M1 malfunctioned, I switched over to my 03a3 using the same reloads. Of the 20 I tried, I could not close the bolt all the way on 6 rounds.
Of the 6, 3 measured 3.250", 2 @ 3.270" and one @ 3.195".

The piston DIA measures .530, and the op rod is a 9 SA. I went through many op rods until I finally found this one. The gray-green park perfectly matches the rifle.

I would like to have this op rod checked out and repaired. Can anyone recommend that can make this like it never happened?

Also, any opinions on why this happened? I've fired thousands of rounds thru the 5 M1's I've had over the years and I've never run into a piston coming off.
I'm wondering if this is screw up on my part, or if it's just a mechanical malfunction?

I apologize how long winded this post is. My fingers never shut up.
Thanks
Chris
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  #2  
Old 06-26-2011, 10:40 PM
denny779 denny779 is offline
 
Join Date: Oct 2009
Location: Conneaut, Ohio
Posts: 210
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http://www.columbusmachine.com/oprod.htm
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  #3  
Old 06-26-2011, 11:39 PM
Ltcboy Ltcboy is offline
 
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Posts: 837
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Get it repaired.
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  #4  
Old 06-27-2011, 04:55 AM
M1Riflenut M1Riflenut is offline
 
Join Date: Oct 2009
Location: New Hampshire
Posts: 2,831
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Just a part failure, probably nothing wrong on your part. I've seen them loose before, never had one come off on me but most likely would have if I had shot the loose ones I've had in the past. I sent a number of them to Jim Swartz back when he was fixing them, now Columbus Machine has taken over for him. I have'nt used them myself yet but will be soon as I stumbled across an early uncut gas trap oprod that needs a piston and tab repair.
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  #5  
Old 06-27-2011, 08:45 AM
MXLMAX MXLMAX is offline
 
Join Date: Oct 2009
Location: Virginia
Posts: 1,545
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Just proves again that a "part" is a man-made device that can and will fail. That is one I haven't heard of before either.
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  #6  
Old 06-27-2011, 10:36 AM
togor togor is offline
 
Join Date: Nov 2009
Posts: 666
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Well .530" for a piston diameter measurement, if accurate, is significantly oversized compared to the USGI spec range of .5260 +0"/-.0008" So it could be that you're measuring a bur or that at the accuracy limits of your instrument. On the other hand, if it is truly that diameter, it could speak to a replacement that was done at some time, maybe not quite correctly. As others have said, op rods can be repaired. Mike Stacey at Columbus Machine is doing good work these days.
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  #7  
Old 06-27-2011, 12:10 PM
themerc themerc is offline
 
Join Date: Jun 2011
Location: Georgia
Posts: 6
Default Jim Swartz

Mike Stacy does do great work...so I am not at all saying don't go to him. However, Jim Swartz is doing a limited number of op rod repairs again. You may want to email him at: JSwartz280@aol.com and ask. He taught Mike Stacy how to rebuild op rods. Jim has also written a number of articles in the GCA Journal about op rod inspection and repair over the past several years. EAN
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  #8  
Old 06-27-2011, 11:35 PM
terrapin88 terrapin88 is offline
 
Join Date: Mar 2010
Location: Massachusetts
Posts: 6
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Thanks for all the replies guys. I've been reading about Mike and Columbus machine. Nothing but praise. Looks like using him or Jim Swartz is want I'll do.

I assumed mechanical failure, but the fact that the reloads I was using were the first I've done up in about 2 years made me wonder if I was rusty and hosed something up.

As far as the piston is concerned, it makes sense that it's likely to be a replacement done at some point. I didn't get the rod from the CMP IIRC. Probably ebay.

Thanks again for the help. I haven't been on this forum in a good few years. So long I had to sign up again, but I see the helpful sort of folks are still here.

C-
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  #9  
Old 06-28-2011, 08:26 AM
ceresco ceresco is online now
 
Join Date: Oct 2009
Posts: 5,349
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Kuhnhasen...."Piston Removal" "Insert punch and impact to see if piston can be removed without heating". Clearly the forces normally applied to the piston tend to keep it on. I would clean it up and silver solder it back on. Good Shooting......
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