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Op rod issue?

This is a discussion on Op rod issue? within the The M14 forums, part of the M14 M1A Forum category; I have some concerns about my SAI M1A Bush. First off, let me say that there have been no function issues in 540 rounds. Not ...


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Old January 10th, 2010, 10:14 AM   #1
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Op rod issue?

I have some concerns about my SAI M1A Bush.

First off, let me say that there have been no function issues in 540 rounds. Not one failure. However, something does not seem right.

It does not cycle smoothly by hand like my M1A NM. At about the halfway point of retracting the op rod it becomes noticeably more stiff, and you can hear and feel the rod running over the spring. The spring has telltale contact marks. I have swapped out parts with a Sadlak NM guide rod and Tubbs chrome silicon spring, and it only seems to get worse. The op rod has some small peening where it apparently contacted the receiver, and it seems to have a subtle bend compared to my NM. The inside of the op rod(where the spring rides) is somewhat rough with machining marks, but there are no obvious burrs or ridges. It passes the "tilt test" without any problem.

Is this a "they all do that situation," does it need to go back to SAI, or should I just break down and buy an SEI op rod?

Could it be something other than the op rod, like an out-of- spec connector lock groove?

Thanks.


Last edited by EBRfan; January 10th, 2010 at 10:26 AM.
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Old January 10th, 2010, 11:00 AM   #2
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First, with any M1A, particularly a brand new one, when you pull the op rod back half way, the bolt is going to ride on top of the hammer and you will feel a noticeable resistance there as the underside of the bolt pushes the hammer down.

Make sure you have plenty of grease on the underside of the bolt, the top of the hammer, and the inside of the op rod tube.

Retract the bolt with the safety on and see if there is a diff. There should be. Also, I'll bet your op rod is an SAI cast unit.

They have been known to be out of spec. in the tube area and/or even rough inside.

Also, sometimes using the NM spring guides can cause issues with smoothness. As you say, it got worse with the NM guide.

"Punishment" marks will appear on the bolt, op rod, and receiver. They are generally normal as the rifle's parts break in and as long as they don't become noticeably larger and larger.

All that being said, The first thing I would do IF I bought a new SAI rifle at this time would be to replace the op rod, bolt, and complete trigger group with USGI units.

Just doing that will likely smooth out the action. IMO, from recent pics posted on this board of the cast parts SAI is assembling their rifles with these days, they just look like junk.
In particular, the trigger housings-whew!

Your rifle appears to function just fine with those parts so, it's up to you to use them until they fail/wear out, or replace them with USGI parts. I don't think there is a valid reason to send it back to SAI.


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Old January 10th, 2010, 11:12 AM   #3
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Thanks for the advice. It is well greased. Only the trigger group is USGI. The rest is SAI, as you expected.

Is an op rod a "drop in" part, or does it require fitting?

Does anyone have any experience with the new SEI op rods in an SAI rifle? In my experience, the quality of their parts is first rate. Or should I just try to find a USGI rod?

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Old January 10th, 2010, 11:28 AM   #4
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Originally Posted by EBRfan View Post
Thanks for the advice. It is well greased. Only the trigger group is USGI. The rest is SAI, as you expected.

Is an op rod a "drop in" part, or does it require fitting?

Does anyone have any experience with the new SEI op rods in an SAI rifle? In my experience, the quality of their parts is first rate. Or should I just try to find a USGI rod?
Some drop right in and some require fitting. Sorry I couldn't give you a straight answer, but that is the way they are. OP rods are not that hard to fit if you have the right tools and are paitent. For more info on how to go about it, look up some of Gus Fishers post on the subject.

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Old January 10th, 2010, 11:31 AM   #5
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Your welcome!

An op rod may need fitting. But, it has been my experience that on SAI receivers, they most likely will drop in without any fitting required.

I have many spare USGI op rods and they all will just drop right into my SAI receivered rifles.

Again, in my experience, the Fultons, Armscorp, and LRB's seem to have the op rod fitting issues in various degrees.

As far as an SEI op rod is concerned, I would not hesitate to buy one of their op rods.

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Old January 10th, 2010, 12:00 PM   #6
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There could be a number of things wrong. If your front sight is all the way to the right to achieve mechanical zero without moving the rear sight, then the barrel is over indexed to a point where the op-rod guide is not running with the centerline of the barrel. This will move the front of the op-rod guide to the right and it will mate up off-center to the gas cylinder. If your op-rod is not running along the centerline of the bore, then it is not going to be running on the centerline of the spring guide. That means the spring will be binding inside the op-rod shaft and maybe on the left side (i think). With a standard spring guide it won't be such a problem. A NM spring guide will close the tolerances up a bit and with an over-timed barrel, the problem is intensified.

Op-rod peening is common in newer SAI rifles and it doesn't seem to be a problem.

As far as a remedy goes, I guess it depends on what you are willing to spend. You could send it back to SAI, but if there are no functioning problems, then they may say it's acceptable. You could send it to a reputable gunsmith and have him inspect it using the appropriate gauges and go from there.

If your op-rod guide is not running on the centerline, then there may be enough play to allow the guide to be rotated if that is the problem.

How old is your bush model and how old is your NM? (just curious).

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Old January 10th, 2010, 12:09 PM   #7
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same same

Quote:
Originally Posted by EBRfan View Post
I have some concerns about my SAI M1A Bush.

First off, let me say that there have been no function issues in 540 rounds. Not one failure. However, something does not seem right.

It does not cycle smoothly by hand like my M1A NM. At about the halfway point of retracting the op rod it becomes noticeably more stiff, and you can hear and feel the rod running over the spring. The spring has telltale contact marks. I have swapped out parts with a Sadlak NM guide rod and Tubbs chrome silicon spring, and it only seems to get worse. The op rod has some small peening where it apparently contacted the receiver, and it seems to have a subtle bend compared to my NM. The inside of the op rod(where the spring rides) is somewhat rough with machining marks, but there are no obvious burrs or ridges. It passes the "tilt test" without any problem.

Is this a "they all do that situation," does it need to go back to SAI, or should I just break down and buy an SEI op rod?

Could it be something other than the op rod, like an out-of- spec connector lock groove?

Thanks.
EBRfan, that is exactly what I is going on with a recent M1A scout purchase. This one was built by a reputable armorer and is all USGI parts except the "SAI" oprod. It is not the bolt hammer contact. That is a distinctly different feel. Keep the great trouble shooting tips coming guys. I'll try them too.

OH, this rifle has a standard spring guide.

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Old January 10th, 2010, 12:59 PM   #8
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The Bush rifle was built 11/5/07 and is SN 209XXX.

The NM was built 4/12/07 and is SN 199XXX.

The front and rear sights are very close to centered for mechanical zero.

The op rod and bolt slide back and forth easily, without binding, without the spring and spring guide in place.

I can't really tell which side of the spring is rubbing, as the wear marks are now all the way around. However, when operating the rod somewhat slowly, you can distinctly feel the op rod tube going over the individual coils of the spring. It sounds a bit like a zipper.

There is a slight bow in the op rod arm in the vertical plane. I can see this by eyeballing the gap to the receiver as I run the op rod back and forth. I didn't measure it, but it probably is not more than .010" difference.

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Old January 10th, 2010, 02:51 PM   #9
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Quote:
Originally Posted by EBRfan View Post
...It does not cycle smoothly by hand like my M1A NM. At about the halfway point of retracting the op rod it becomes noticeably more stiff, and you can hear and feel the rod running over the spring. The spring has telltale contact marks...
What you are describing is exactly how my Super Match felt when cycled by hand after about 100 rounds. The problem turned out to be an op rod guide which walked around the barrel because SAI had not secured it properly. That shouldn't be happening in your case because the Super Match with a stainless steel barrel doesn't use an op rod guide roll pin to keep it more or less in place, while your Bush rifle does.

Read tonyben's description of how to check the alignment of the op rod vs the barrel. If it's off, first, I'd check the guide to see if there's actually a roll pin in the hole on the side of the guide going crosswise just above the bottom of the barrel. That should keep the guide from rotating very far, if at all. If it's missing, that's something SAI should fix. If the pin is in place, it may be possible to get the guide more in line with the barrel, but it's also possible to collapse the hole the op rod goes through if you're not careful. Also, the guide tends to want to walk around the barrel because the op rod isn't going straight back; it's being resisted off to one side (the bolt roller), which makes the op rod want to move in the opposite direction and it's just kept aligned by the guide. So if you can drive the guide back to a centered position, it'll probably just go back to where it was before you fixed it. Ask me how I know.

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Old January 10th, 2010, 05:19 PM   #10
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The op rod guide appears centered. The pin is in place under the barrel. The end of the op rod lines up centered on the gas piston. The other end, however, reveals the problem. The opening for the tube where the spring resides is not lined up with the connector lock. It is clearly off to the left (looking from the bottom). My op rod arm appears to have a little bit of twist in it as well.

Looks like I may need a new op rod. Thanks for all the suggestions/advice so far. Any others at this point?

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Old January 11th, 2010, 02:35 PM   #11
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I had an oprod with a bent tube on an SAI preban a while back. It acted exactly as you describe, moved smoothly about an inch or so then tension built and it got very tight at the end. I got a new oprod and it now works fine.

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Old January 29th, 2010, 04:22 PM   #12
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Update

Problem solved. New forged SEI op rod is a drop in fit. She now cycles smoothly. Thanks to all.

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