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Old February 16, 2020, 17:08   #1
jacmec
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DSA Scope Mount FTE

I'm having some troubles with a DSA scope mount causing FTEs. The rifle, a DSA Izzy, runs fine with the standard dust cover. I've uninstalled and reinstalled the mounting plates 3 or 4 times now, each time ensuring that the carrier is able to drop free without binding. I've gone back through the gas setting procedure just to make sure. I've inspected inside the mount for any obvious signs of rubbing, no hints there. The ejection port is kind of chewed up from brass hitting it, maybe a clue?

I get a mixture FTEs. Stove pipes. Complete FTEs, where the empty case is in the chamber. And 180 degree jams, where the case rotated around and the case mouth is up against the bolt face.

My gut reaction is to dremel the sharp edges around the ejection port, if that fails then try polishing the inside of the mount. Or just see if DSA will give me a refund and try an ARMS mount.
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Old February 16, 2020, 17:19   #2
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I've seen this before. The bolt carrier will slide right in, but under load during recoil, it scrapes just enough to retard function.

Take it off the rifle and inspect it very carefully for any indication that something rubbed on the inside. It doesn't take much. Just a thin sliver of silver along an edge. Pay particular attention to the retaining plates.

If you find a spot, a little file work in that area might solve your problem.

Where do you think you can buy an A.R.M.s mount?
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Old February 16, 2020, 17:26   #3
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Thanks, I'm looking it over right now and not seeing any bare metal but I do see two small spots where the finish looks blemished. Maybe I'll start there and see what happens.
Are the ARMS mounts rare or discontinued? They have them listed on Brownells currently.
https://www.brownells.com/optics-mou...prod27289.aspx
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Old February 16, 2020, 17:41   #4
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Quote:
Originally Posted by jacmec View Post
Thanks, I'm looking it over right now and not seeing any bare metal but I do see two small spots where the finish looks blemished. Maybe I'll start there and see what happens.
Are the ARMS mounts rare or discontinued? They have them listed on Brownells currently.
https://www.brownells.com/optics-mou...prod27289.aspx
I thought they were but I guess not. Last time I looked for one I couldn't find the FAL version anywhere.
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Old February 16, 2020, 19:08   #5
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I have both mounts and I gotta say the ARMS mount is the best.
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Old February 16, 2020, 19:18   #6
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Sometimes you have to shorten screws to prevent screw tips from sticking out which causes bolt carrier to bind.
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Old February 16, 2020, 19:26   #7
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Quote:
Originally Posted by jacmec View Post
Thanks, I'm looking it over right now and not seeing any bare metal but I do see two small spots where the finish looks blemished. Maybe I'll start there and see what happens.
Are the ARMS mounts rare or discontinued? They have them listed on Brownells currently.
https://www.brownells.com/optics-mou...prod27289.aspx
That's about right for the ARMS #3. You can find them used here from time to time for around $90+. I'm a fan because they are pretty decent and still can take them off without screwing around with the clamps plus you don't have to pad the receiver to not mar it. Maybe not as stable as the DSA, but quite the improvement over the original scoped dust covers that sit up a mile high on that stamped piece of sheet metal.
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Old February 16, 2020, 21:04   #8
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Remove it.

Inspect threads on locking plates for cross-threading.

Install each screw into locking plate to confirm integrity of threads.

Re-install mount on receiver, inspecting for engagement of locking plates to FULL DEPTH in inner slots of receiver.

Test for function.

One youíve un-fugked the engagement issues, remove mount again, and secure each screw with BLUE Loctite. If you donít use Loctite, the mount WILL shoot loose.
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Old February 16, 2020, 23:40   #9
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Quote:
Originally Posted by W.E.G. View Post
Inspect threads on locking plates for cross-threading.
You might be on to something here. One screw definitely has messed up threads.
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Old February 17, 2020, 00:24   #10
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I had the BC hitting the claw plates inside. Found not all were hooking
the edge the same way, and all were at different heights away from
side and some had "rub" marks. Had to file and stone each claw into its
position, and mark so they go back into same position. . . . PIA !
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Old March 16, 2020, 05:47   #11
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Since I last posted I replaced one of the screws and remounted it. Checked, rechecked, and triple checked the alignment of the each plate. Took it too the range and again had multiple jams per mag.
Took it back home, uninstalled and started to file the sharp edges on each plate. Didn't go crazy, just used a hand file and went slow. Reinstalled and took it out again. This time I was able to through one mag without a problem. But one FTE (and even an odd FTF) per mag for the rest of the trip. So things have improved but it's still not 100%.
I've decided I'm done with it. I placed an order for an ARMS mount and contacted DSA to see if they can get me a refund.
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