M14 Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
186 Posts
Discussion Starter · #1 ·
Gun smith just put a new barrel on and I am getting friction when the op rod is fully rearward, even with the bolt out. The receiver is a 2001 SAI and the new barrel is a 1990's Wilson NM standard weight. My old barrel was a heavy krieger. So Im going from a heavy barrel (which had no binding) to a smaller barrel which now has binding.

I've tried bending the op rod slightly outward (i prob didn't apply enough pressure to do anything out of fear of tweaking it too much) and I also hit the surface on the op rod where it is contacting (near the roller cutout) the receiver with some high grit emery paper to polish it up.

After doing this the op rod doesn't bind as hard but still will not fall forward on its own weight to pass the tilt test.

A few things I am thinking:
1) Check the op rod guide on the barrel, might be out a little. smith said they trued it to the receiver/barrel
2) Hit the receiver with the emery paper to polish the area where its contacting.
3) Shoot it and watch the area for excessive wear. As long as there are no failures to load and the bolt is picking the round up and putting it into battery I may be g2g?
4) Oh yea, take it to a gun smith... but Id like to fix it myself if I can. Id hate to wait a few weeks for some little tweak I can make myself.

Here is the area (in red) I am talking about, this is NOT my receiver
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #4 ·
Who's op rod?
stock SAI

Two things: 1) What did he mean by indexed to the rcvr and bbl?
just meaning "trued up" so its aligned correctly.

the op rod guide is easily adjusted if need be.
care to expand? what methods to adjust it?

do the tilt tests some more to see if grease is coming off the op rod in travel or being deposited back near the receiver heel., or both.
will do, and what would you say if grease was either being deposited or collected by the op rod?

honestly from looking at the wear, the red mark in my post appears to be the only contact/friction point where its binding
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #7 ·
wow thanks for the reply's gentlemen. GI1

1. With the first barrel in the gun, was the oprating rod aligned on the piston? If it wasn't, that alone could be the reason. The guide might have been placed slightly off center so the op rod did not bind up.
The gun started with a scout barrel. Funny, I do recall the op rod being slightly off center as it hits the piston.

2. The op rod guide is a bit too far to the right when viewed from the rear and that pushes the op rod too much on the right side. That would cause the top of the op rod handle to bind back there on the receiver.
can i give it a few love taps with a rubber mallot? or do i have to remove the pin?

PLEASE do not grind, file, cut or sand on the op rod lug or op rod channel in the receiver to correct the problem.
i understand, but to be clear i only polished a small area on the inside of the op rod. basically the part that is contacting the receiver. i have not touched the lug or channel.

If you blacken the curved portion of the op rod saddle with Magic Marker, you may see rub spots where it is hitting the barrel enough to cause this problem. Sanding the op rod where it rubs normally cures that.
i looked at that actually last night and i do not see any wear in that area, however i do recall it being tight... i dont think it would pass a paper test. so i can sand down the saddle of the op rod if its contacting the receiver?

If that is not binding and the op rod is centered on the piston, then slightly bending the rear of the op rod should allow it to slide freely.
knowing my original barrel had the op rod guide tweaked slightly off-center, would you recommend I bend the op rod and keep the guide "true" to the piston? or tweak the op rod guide?

If you need to move the op rod guide a hair left or right you can do it with a block of wood and a hammer without pulling and replacing the pin. Sometimes the edges of the op rod guide can be a little jagged. A file will clean that up.
noted on the jagged guide. its a new one from brownells, Ill give it a look

OK, the other. SAI has made some receivers off and on that have to be slightly relieved back there to clear the bolt roller. The unwanted contact typically begins under or just behind the rear sight cover. First order of business is to determine whether that's in fact happening and precisely where. Some shooters here have resolved it by kissing the site of the contact with the Dremel tool.
this bolded part sounds like what i have. with three options (1) tweak op rod guide, (2) bend op rod, (3) relieve the contact point (least favorable option). Im going to start with #1 i suppose

But let me repeat, I'd try a good-condition USGI op rod before I reached any conclusions. The geometry of your SAI op rod's travel may have been fine with the hvy bbl and its op rod guide, but that doesn't necessarily equate to in-spec. I KNOW your GI contour Wilson barrel, correctly indexed, will work good with a HRA, WRA, SA, or TRW op rod because I've used several of those barrels and op rods in combination over the years.
good advice, but i dont think i want to take it... yet
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #10 ·
I was able to remove a little bit from where it was rubbing on the op rod. You can see it starting about half way up on the right side and tapering off as it goes to the left. This was the contact point that was rubbing. Tilt test passed!


bd, it started as a scout, then i went heavy barrel, now im doing a standard weight barrel... final answer :)
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top