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9/22/2017 12:11:25 AM
Posted: 8/19/2005 3:20:06 PM EDT
[Last Edit: 8/19/2005 6:55:02 PM EDT by AR-Poor]
I just finished my first M92 build and I need a little assistance from the gurus. When I work the action the bolt carrier locks to the rear. I can strike it with a hard object to get it to move slowly forward. The bolt carrier also locks back half way to the rear when I move it back slowly. I removed the hammer and the rest of the FCG to make sure that the bolt carrier isn't rubbing on the hammer.

The receiver is a new 1.0mm Armory USA stamped from Ohio Rapid Fire. The kit is an ORF M92.

I guess I need to sand the rails down to fit. Is the receiver warped at the rear? Thanks for the help.
Link Posted: 8/19/2005 5:29:46 PM EDT
What receiver did you use??

Some rail filing is normally required for smooth functioning.. This is normal.. You may want to measure the width of your receiver along the whole top.. I have had to bend a few out, and in on some builds.. I used a set of Quick Grip clamps to both squeze and spread receivers before... But most likely all you need is a little filing.. Go slow, and test your carrier often..

As for the rail sliding?? What rail are you refering to.. None of your rails should move at all.. Only the blot carrier...


Link Posted: 8/19/2005 6:56:42 PM EDT
I meant bolt carrier. It is extremely tight and is difficult to install on the rails after a field strip of the weapon. Thanks.
Link Posted: 8/19/2005 9:32:22 PM EDT
I had one receiver that was slightly warped in the rear stock block area. The cut outs for the bolt carrier insertion were just a tad too tight also. I opened them up with a file - a little bit at a time, file and fit, file and fit, etc. until it went in.
The corners of those cut outs can also cause the bolt carrier to lock up on full retraction. I messed with it quite a while and it got better but still did it occasionally. I put in a reoil buffer on the recoil spring which limited the rear travel some. No problems since then.
Look for slight malformations on the corners of those frame cut outs where you insert the bolt carrier. If you have had to rap the bolt carrier with a hammer, you will have slightly burred the corner that is hanging. Smooth it out some.
Another way of doing it is to slightly round the corners on the slots on the bolt carrier where it rides in the top rail.
Don't go overboard removing the metal. Too much and the bolt carrier will jump out almost every time it is retracted. If that happens, you will HAVE to use the recoil buffer to limit the bolt carrier travel.
Good Luck!
Link Posted: 8/19/2005 9:53:35 PM EDT
Link Posted: 8/20/2005 4:31:57 AM EDT
[Last Edit: 8/20/2005 4:34:08 AM EDT by Anthropy]
Does it have trouble when you move the carrier fast and let it go, or just when you do it really slowly? My SAR1 will hold the carrier back if I slowly move the carrier rearward and then slowly release it. Mind you, if I give the weapon a smack, the carrier will slam home.

If it does not hinder function when you are shooting it, I would not worry and let it break in the rest of the way. IF it holds the bolt back when you shoot it, then you need to fine tune it.

edit: I just re-read your post and did not realize that yours was not hanging on the fcg. I hate mornings before coffee is introduced into my system.
Link Posted: 8/20/2005 2:54:45 PM EDT

Originally Posted By jnewt:
A few of the latest batch of Armory receivers seam to have had a step in the manufacture missed. I have had several which Armory did not machine the top rails. Not a biggie if you own a dremel and a work bench though. Take down the rails, even on each side till your bolt carrier moves freely.


The top rails are too wide, not enough clearance for the bolt carrier to travel back and forth?
Just wondering. I have a couple of Armory receivers coming.
TIA
Link Posted: 8/20/2005 4:19:14 PM EDT
I gently sanded and dremeled the upper and lower rails to thin them out. Then I shined them up with some gun oil. It is still a little rough but works pretty well.
Link Posted: 8/21/2005 4:52:14 AM EDT
My Romanian had similar symptoms:
www.ar15.com/forums/topic.html?b=4&f=51&t=72847

Link Posted: 8/21/2005 10:55:44 AM EDT
All of my Armory/GT receivers were loaded with burrs all over the rails that needed filing and sanding to get them right.

Make sure your bolt carrier group is not hanging up on your hammer or ejector. Easiest way to check this is to take your top cover off and observe the movement of your bolt carrier group from above and below. You can see if your bolt is hitting your ejector by looking up the magwell from below. If it makes contact, it will push the bolt to the right. Be careful trimming the ejector.

I would be wary of widening your rails because your trunions will automatically space them out correctly.

Once you get it moving, shoot the piss out of it and it will probably correct itself
Link Posted: 8/21/2005 12:56:52 PM EDT
I used a dial caliper to measure between the top rails and the bolt carrier slots to make sure I had a close but loose fit down the rails. On the last one I built, the bolt carrier was 0.97" between the slots. I opened the top rails to .99" to 1.01" down the frame and it ran fine. I don't remember what the measurement at the rear for the bolt insertion cutouts but it seems like it won't be much more than 1.10".
Sometimes a dial caliper will make things a lot easier in a trial and fit situation.
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