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Posted: 2/28/2015 9:08:38 PM EDT
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A while back, I posted pics of my SCAR 17 malfunctioning with a suppressor attached. It was overgassed, and the bolt carrier was hitting the back of the receiver (the plastic butt stock) hard enough to bounce the next loaded round out of the mag on occasion even with the gas regulator in the suppressed setting. Well, today I finally got around to fixing it and wanted to share my findings.
The stock gas control screw was 1.5mm. I ordered all the screws from midwest gun works between 1.20 and 1.45mm. I settled on using the 1.35mm screw after trying all of them. It still cycled with authority, locking the bolt back on the last round, etc even unsuppressed. But with the suppressor, the recoil was MUCH less than with the stock gas screw, it didn't sting my cheek, and more importantly there were no malfunctions. About 60 rounds were fired after fixing the issue; all fired flawlessly. 3-4 rounds were put in the mag each time to test the bolt locking open on the last round. Of course, this post required a pic: 
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Ammo: Privi Partisan 145 gr. 7.62
Unsuppressed gas setting/ No suppressor AAC 51T muzzle device 1.20mm: Did not eject spent case. 1.25mm: Ejected spent case, did not chamber next round in magazine 1.30mm: Ejected spent case, chambered next round. Bolt locked open intermittently on last round in magazine. 1.35mm: Functioned perfectly, bolt locked to rear on last round in magazine every time. After reaching this point, I used the AAC 7.62 SDN-6 with the regulator on the suppressed setting. Ammo: Privi Partisan, Winchester 150 gr. power points 1.35mm: Functioned perfectly with both ammo types. No issues at all, recoil was significantly reduced compared to the stock 1.5mm gas control screw. Bolt carrier is not hitting the rear of the receiver nearly as hard. Gun runs much smoother. |
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Interesting information... Anyone have any input on whats listed here? http://handldefense.com/product/scar-gas-control-jet/ Edit: and whats needed to remove the stock gas screw, thought I remembered mention of a special tool, but looks like a small enough hollow bit driver would work... |
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Not the OP, but I get my SCAR parts here: http://www.midwestgunworks.com/page/mgwi/ctgy/scar-parts I didn't even look at the sizes Handl offered, they seem way off compared to stock... |
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Quoted:
Not the OP, but I get my SCAR parts here: http://www.midwestgunworks.com/page/mgwi/ctgy/scar-parts I didn't even look at the sizes Handl offered, they seem way off compared to stock... Midwest Gun Works is where these came from |
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1919man, thanks for the good info.
I really don't understand why they didn't select a gas screw or a gas system that would prevent this problem from the beginning. I thought the whole point of my SCAR's adjustable gas block was so that I wouldn't need to deal with this problem? I guess FN had no intention of selling something to civilians for suppressed use (considering their barrels lack an appropriate shoulder), but if the SOCOM AAC cans had to be modifed for this gun, then they have a design issue that needs to be addressed. This makes me want to trade it in for an AR-10 variant. I only have about 200 rounds through my suppressed SCAR-17 with a Surefire SOCOM 7.62 can, and I haven't had any issues with the gas block set to suppressed mode. Work is what prevents me from taking it out to the range these days.  When I shoot it more later this year, I'll try to see if I wind up breaking the damn thing before I change anything around. For a $2.5k rifle, it should work as intended.
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Quoted:
1919man, thanks for the good info. I really don't understand why they didn't select a gas screw or a gas system that would prevent this problem from the beginning. I thought the whole point of my SCAR's adjustable gas block was so that I wouldn't need to deal with this problem? I guess FN had no intention of selling something to civilians for suppressed use (considering their barrels lack an appropriate shoulder), but if the SOCOM AAC cans had to be modifed for this gun, then they have a design issue that needs to be addressed. This makes me want to trade it in for an AR-10 variant. I only have about 200 rounds through my suppressed SCAR-17 with a Surefire SOCOM 7.62 can, and I haven't had any issues with the gas block set to suppressed mode. Work is what prevents me from taking it out to the range these days. When I shoot it more later this year, I'll try to see if I wind up breaking the damn thing before I change anything around. For a $2.5k rifle, it should work as intended.
The rifle does work as intended. The scar barrel shoulder is minimal for weight savings (as is the entire barrel profile), and for the most part, until very recently, military's of the world didn't use or issue suppressors on rifles. Further, the FNH scar specific suppressor is designed to work on the scar as made from the factory. Even AAC modified its SDN-6 for issue on the scar rifle. The issue here is more from the suppressor being used then the rifle it is being used on. Note the AAC SDN-6 suppressor being used is not the new technology surefire SOCOM suppressor you are using. Surefire dumped its entire old line in favor of the SOCOM line and the improvements made to run on the new rifle technologies coming out. Further, surefire makes a scar specific suppressor and muzzle device that overcomes over gassing, and the small shoulder for muzzle devices. (NOTE: I am not a surefire fan boy. The surefire is what I have, and what I am working with. The AAC SDN-6 is an excellent can and works well too.) I am interested in this topic since I run an old school surefire SS762 can (an older reflex design no longer made). I too have noted what I consider over gassing on my rifle with the suppressor attached. I haven't experienced malfunctions from running suppressed, but the action speed and violence of recoil is higher then when run without the suppressor attached. I too have been thinking about experimenting with smaller gas screws (I call em gas jets since they are very much like carburetor jets from Holley carbs). With the OP doing the initial testing, I can limit my purchases to two sizes and do my own testing. |
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Quoted:
Not the OP, but I get my SCAR parts here: http://www.midwestgunworks.com/page/mgwi/ctgy/scar-parts I didn't even look at the sizes Handl offered, they seem way off compared to stock... The gas screws are #8 if anyone is looking at this diagram. |
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Quoted:
The gas screws are #8 if anyone is looking at this diagram. Quoted:
Quoted:
Not the OP, but I get my SCAR parts here: http://www.midwestgunworks.com/page/mgwi/ctgy/scar-parts I didn't even look at the sizes Handl offered, they seem way off compared to stock... The gas screws are #8 if anyone is looking at this diagram. My black 17 one is so-overgassed that it craters primers on my reloads that show no pressure marks in any of my other 308s. I'm going to try the 1.35 and 1.40 screws, thanks to you. It'll run without issue on suppressed, without the suppressor, too. My FDE 17 wasn't as bad, but I'm getting back my barrel from Marvin tomorrow. He cut the barrel to 13.7 and pinned a MAMS on it to take it to 16.1". Hopefully, the 2.3 inches he lopped off will reduce the gas pressure. |
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