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Discussion Starter #1
I went to the range at fist time for my scar 29s in 6.5 creedmoor.
Every time I loaded and shot 4-6 rounds and cleaned the barrel. Scar 20s wouldn’t lock open and had a few times failed to feed new round.
The gas regulator is on 12 o’lock position and ammo I used was 2boxes of hornady 140 ELD.
After got home I disassembled the barrel from upper and checked the gas piston and gas jet,everything looks ok to me.
Also with empty fn 10rd mag inserted , pulling the charging handle manually, bolt will locked open.
I had scar 17 for years never had similar problems.
Any suggestions?
 

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did you completely break down the rifle and clean it, then lube and reassemble before taking it to the range?
mine had some kind of packing grease all over and had to be cleaned (per the owners manual).
note that i only have the 7.62x51mm version
 
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Discussion Starter #5
did you completely break down the rifle and clean it, then lube and reassemble before taking it to the range?
mine had some kind of packing grease all over and had to be cleaned (per the owners manual).
note that i only have the 7.62x51mm version
Yes I did completely clean it and re did yesterday. The rifle still will it lock back and also today had a few light primer strikes.
 

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These latest rashes of FN's lack of quality control in both R&D and manufacturing reminds me of SIG Sauer America.

FN Herstal needs to sit down and ask itself if it wants to be known as a second rate small arms manufacturer.
 

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Is there any wobble in you butt stock ? There is a nut that doesn't come loc-tited inside the stock. If it comes loose, your rifle will malfunction with fails to lock back and even feed. Check that nut to be sure it's tight.
 

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I'm willing to guess you have a gas port pressure issue where not enough pressure to move the bolt fast enough for bolt hold open to work.

This is not a new issue, there have been several instances of this problem with several 6.5mm/6mm Creedmore/260 Rem semi-auto gun models.

The problem is these cartridges often use a very wide range of powder burn rates, even with factory ammo.

If possible, you must tune the gas port setting to the ammo you shoot. Different ammo may require different settings.

I recommend loading only one round in a magazine when testing the gas setting.

Do this until you get a failure for bolt hold open or if your brass ejects at 3 o'clock from the bolt/receiver.

Turn the gas setting up one setting and re-test with only one round in the magazine. If there is no detents, very small consistent adjustments.

Stop and turn the gas down if you get ejection from receiver at 1 or 2 o'clock.

You are looking for the minumum gas setting to get you bolt hold open consistently.
 

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Discussion Starter #13
Is there any wobble in you butt stock ? There is a nut that doesn't come loc-tited inside the stock. If it comes loose, your rifle will malfunction with fails to lock back and even feed. Check that nut to be sure it's tight.
The cheek raiser wobble a lot.
Which nut are you talking about ?
Could you be more specific? Thanks.
 

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Discussion Starter #14
I'm willing to guess you have a gas port pressure issue where not enough pressure to move the bolt fast enough for bolt hold open to work.

This is not a new issue, there have been several instances of this problem with several 6.5mm/6mm Creedmore/260 Rem semi-auto gun models.

The problem is these cartridges often use a very wide range of powder burn rates, even with factory ammo.

If possible, you must tune the gas port setting to the ammo you shoot. Different ammo may require different settings.

I recommend loading only one round in a magazine when testing the gas setting.

Do this until you get a failure for bolt hold open or if your brass ejects at 3 o'clock from the bolt/receiver.

Turn the gas setting up one setting and re-test with only one round in the magazine. If there is no detents, very small consistent adjustments.

Stop and turn the gas down if you get ejection from receiver at 1 or 2 o'clock.

You are looking for the minumum gas setting to get you bolt hold open consistently.
It will still fail even I just load one round a time. I tried.
When you said tuning the gas port setting, do you mean to buy different gas jets and try them all ?
 

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I'm willing to guess you have a gas port pressure issue where not enough pressure to move the bolt fast enough for bolt hold open to work.

This is not a new issue, there have been several instances of this problem with several 6.5mm/6mm Creedmore/260 Rem semi-auto gun models.

The problem is these cartridges often use a very wide range of powder burn rates, even with factory ammo.

If possible, you must tune the gas port setting to the ammo you shoot. Different ammo may require different settings.

I recommend loading only one round in a magazine when testing the gas setting.

Do this until you get a failure for bolt hold open or if your brass ejects at 3 o'clock from the bolt/receiver.

Turn the gas setting up one setting and re-test with only one round in the magazine. If there is no detents, very small consistent adjustments.

Stop and turn the gas down if you get ejection from receiver at 1 or 2 o'clock.

You are looking for the minumum gas setting to get you bolt hold open consistently.
it’s a SCAR20S, not an FAL. There are no minute adjustments on the gas regulator.
 

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Discussion Starter #17
when you remove the stock from the rifle, look inside the stock where it meets up with the receiver. There should be two screws inside. Check those screws for tightness.
I will check but no sure that will effect the liability.
 

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I will check but no sure that will effect the liability.
It absolutely will effect the reliability. I've seen it first hand. I started a thread on it a few months ago. I witnessed my buddies SCAR 20 (7.62 x 51) fail to lock back and fail to feed over it. The butt stock was wobbly, and one of the inner nuts had come loose. It was loose enough to be able to wobble the stock a little bit. I think you would notice it if that was the problem though. But it still doesn't hurt to check them. The butt stock plays a crucial role in the cycling of the SCAR. But again, if that was the problem with your rifle, I think you would have noticed the butt stock being loose. I don't know how loose it has to be to cause a problem, but it most certainly can. There was a vid posted about it somewhere out there.
 
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