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  #1  
Old 10-14-2019, 08:23 PM
MooseMoose MooseMoose is offline
 
Join Date: Oct 2019
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Default Short Cycling CMP Special

So I picked up a CMP Special grade about 3 years ago. Life got in the way and I'm only now getting around to shooting it (I know...I know...) The problem is that it's short-cycling on pretty much every other round, leaving the spent casing in the chamber and requiring manual cycling.

First time it did this I got it home and found the gas plug was loose. Aha! Tightened it to 10 ft-lb.

Next time I took it out same problem. This time I did a full detail strip. Op rod & bolt pass the tilt test and op rod isn't rubbing the stock. There was some grease from the CMP, but overall the action was pretty dry so I greased it up pretty good. Operating spring seemed okay but I put in a new one anyway. Measured the op rod piston diameter, however, and got like 0.5245-0.5240 all around

Pretty bummed about that, as from what I'm reading that may be the problem. Any other suggestions before I get the piston worked on, or is that the most likely culprit at this point? I need to get it out to the range again, but is it too optimistic to hope the additional lube and new spring might help?

Ammo I'm using is American Eagle's M2 ball equivalent. I've tried both new manufacture clips and an older GI clip and that didn't seem to make any difference.

Any suggestions greatly appreciated.
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  #2  
Old 10-14-2019, 08:44 PM
ARB ARB is offline
 
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I think this checklist has some pretty good advice: http://www.garandgear.com/m1-garand-failed-to-cycle. Hope this helps...
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Old 10-14-2019, 08:45 PM
sachst sachst is online now
 
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This sounds, if my brain is not fogging, that it may be more an issue with failure to extract, which would point to extractor/spring or ammunition case issues, perhaps take a look at the chamber as well for blurring or binding. FWIW.
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Old 10-14-2019, 09:34 PM
Shomway Shomway is online now
 
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Since "Specials" have a fresh repark you might want to give it time for some of the park to wear down/break in. Get a chamber brush and give it a good cleaning...can't hurt!
Your piston is a bit below the min. but usually it takes a combination of an out of spec (<.525 is out of spec) and a worn gas cylinder to cause frequent malfunctions.
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Last edited by Shomway; 10-14-2019 at 09:44 PM.
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  #5  
Old 10-14-2019, 11:44 PM
MooseMoose MooseMoose is offline
 
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Pretty sure it's not FTE as the bolt isn't coming back far enough to strip a new round.

Unfortunately I don't have a way to measure the cylinder so no idea if that's an issue too. But that at least gives me some hope that it might work after some break-in even with the underspec piston.

Forgot to mention that I also cleaned the poppet valve on the gas plug: that seems fine.

I assume the AE ammo is good to go? I didn't want to use full power .30-06 given the apparent risk of damaging the op rod.
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  #6  
Old 10-15-2019, 07:55 AM
ken792 ken792 is offline
 
Join Date: Mar 2012
Location: VA
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My friend has a Special with an undersized piston head too that won't cycle reliably with any ammo. The bolt goes back far enough to eject empty brass, but not pick up the next round or lock back. He swapped the op rod from his rack grade into it and it usually works fine now.
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  #7  
Old 10-15-2019, 11:57 AM
cea1 cea1 is offline
 
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Location: Helena, MT
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Sounds like you are on the right track with the undersized piston. I'd get in touch with CMP, they've been great to work with on a similar issue for me.
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  #8  
Old 10-15-2019, 01:12 PM
twofeets twofeets is offline
 
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Wasn’t part of the reworking of CMP/Boyd’s stocks removing a bit of wood at the back of the receiver to ensure the bolt is getting full range of backwards travel? Wonder if it could be that.

http://forums.thecmp.org/showthread.php?t=147599
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  #9  
Old 10-15-2019, 03:04 PM
Orlando Orlando is offline
 
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Quote:
Originally Posted by twofeets View Post
Wasn’t part of the reworking of CMP/Boyd’s stocks removing a bit of wood at the back of the receiver to ensure the bolt is getting full range of backwards travel? Wonder if it could be that.

http://forums.thecmp.org/showthread.php?t=147599
That is to keep the bolt from chipping the stock, behind the receiver where its visible
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  #10  
Old 10-15-2019, 05:22 PM
Me Not You Me Not You is offline
 
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My special, when brand new, functioned OK with full-power ammo, but short cycled frequently with old DCM ammo I'd accumulated. A lot of drag, even well greased everywhere, from the new Parkerizing. After a few hundred rounds it cycles with the DCM ammo.
The DCM ammo was reprocessed and left with a charge of around 44gr of what appears to be IMR4895. Gives .30-30 performance with a much louder muzzle blast.
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