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Posted: 1/21/2018 12:09:32 PM EDT
In my recent efforts to replace my SCAR 17 Gas Jet in order to reduce recoil, I had to do a lot of searching for data on what sizes work best. The information is out there, but its scattered. I thought I would start a thread to compile all the sporadic data and put it in one place.
To start, the standard jet sized, according to Parker Mountain Machine's site is: 17S 16": 1.5mm 16S 16": 1.4mm 16S 10.5": 2.0mm (thanks to Spooled) http://www.parkermountainmachine.com/store/p104/PMM_SCAR_16%2F17_Stainless_Steel_Gas_jets.html What I cant find is the starting sizes for the other factory barrels. Please post with your source if you know. SCAR 17S 16": https://www.ar15.com/forums/armory/SCAR_17_Overgassed__With_Solution/24-441832/? 13": http://fnforum.net/forums/fn-scar-17s/105514-gas-screw-size.html SCAR 16S 16": http://fnforum.net/forums/fn-scar-17s/135585-dialing-gas-jet-sizes-scar-17-16-barrel.html 13": 10.5": http://fnforum.net/forums/fn-scar-17s/105514-gas-screw-size.html https://www.ar15.com/forums/Armory/What-gas-jet-are-you-using-in-your-Scar-16-CQC-/24-485361/ Post what you have personally found to work with your barrel length below. Share links to other threads as well that aren't listed above. Hopefully we can make it easier for others to find this data in the future and give good starting points. |
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Great thread, not a fan of the other forums with this info. I can contribute this for now, future testing i do i will report back regarding gas jets on the 16 and 17 i have.
Factory 10 inch barrel for 16S comes with a 2.0 as per FN. |
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I ended up with 1.35mm in my 17. I found 1.30 to still work but with 1.25 the last round hold open was starting to fail. So to be safe I jumped up to 1.35. I definitely felt a difference, and the brass wasn't getting nearly as banged up on ejection, which was a concern since I reload. This was tested with Lithuanian M80 spec GP11 and Federal 168gr GMM ammo. I haven't tried this jet with a suppressor though.
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1.35 on a 16" 17S. Works great suppressed and non. Noticeably smoother.
Suppressor is AAC 762-SDN-6 |
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I'm running the 1.3mm on a 16" scarH. Mature rifle with over 12k rds fired. With this gas jet installed the rifle will not cycle at all in suppressed mode without a suppressor attached. SUPER smooth and flat shooting with and without a suppressor. I'm using the first generation Surefire 762SS suppressor with the Surefire specific scarH flashider muzzle device (no timing or other installation issues with this muzzle device).
The only times this rifle malfunctions is when you let a Francophile gun personality shoot it. |
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My 16 with a 11in barrel has a 1.5 gas control screw. So far no problems with it.
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Well the 1.8 jet installed in a 10 inch 556 barrel is way overgassed using 556 (wolf gold, federal 193, and imi 193)
going down to 1.6, and got a 1.7 for just in case. will post results next weekend |
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I tried out a 1.35 w/ a Saker 762 and recoil feels less sharp and distinct from the 1.50. Whenever the 1.40's become available I am going to grab a couple and think that will be my SCAR's sweet spot.
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Have a stock 17s and a stock 16s. Any benefit in going with a smaller gas jet even if I am not currently running suppressed? They shoot great the way they are, but if there is something to gain from running a new gas jet I definitely would do it.
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Well made some progress with my scar 16 10 inch barrel.
Intial testing with 1.8 gas jet. Surefire socom rc suppresor Ammo used: federal m193, wolf gold, imi m193. 300 rounds fired very lightly lubed, what most would consider dry. 100% reliability on both settings, extreme gas to face suppressed in the suppressed setting. Harsh recoiling, I know recoil is subjective but there was noticeably more than in stock 16 inch configuration. 1.6 gas jet installed surefire socom rc only used the imi m193, 100 rounds fired normaly lubed 100% reliability unsuppressed in 12 o'clock position. For the most part the gun ran fine unsuppressed on the suppressed setting, I had 1 fail to lock back after about round #60, the gun did feel a bit sluggish though, just like it did in 16 inch configuration when shot the same way. Recoil feels about the same as when it was in 16 inch configuration. Way less gas into the face. honestly I think I could run a 1.5, and I might toy with one in the future but for now I'm pretty pleased with it. Attached File |
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So just tried a 1.4 in my 13" SCAR 17. Ran fine unsuppressed, and had one hiccup suppressed, but I think that was from my handload. Honestly was very surprised that the 1.4 worked so well in the 13". Gotta do some more shooting with it to confirm
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Quoted:
Well made some progress with my scar 16 10 inch barrel. Intial testing with 1.8 gas jet. Surefire socom rc suppresor Ammo used: federal m193, wolf gold, imi m193. 300 rounds fired very lightly lubed, what most would consider dry. 100% reliability on both settings, extreme gas to face suppressed in the suppressed setting. Harsh recoiling, I know recoil is subjective but there was noticeably more than in stock 16 inch configuration. 1.6 gas jet installed surefire socom rc only used the imi m193, 100 rounds fired normaly lubed 100% reliability unsuppressed in 12 o'clock position. For the most part the gun ran fine unsuppressed on the suppressed setting, I had 1 fail to lock back after about round #60, the gun did feel a bit sluggish though, just like it did in 16 inch configuration when shot the same way. Recoil feels about the same as when it was in 16 inch configuration. Way less gas into the face. honestly I think I could run a 1.5, and I might toy with one in the future but for now I'm pretty pleased with it. https://www.AR15.Com/media/mediaFiles/297824/56A3A606-AD84-4617-93E9-E26A0CA4B6D5-491708.JPG View Quote I guess I will try the 1.6 first |
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Quoted: i ordered 1.5, 1.6, and 1.7 for my 10.5" I guess I will try the 1.6 first View Quote i am 700 rounds in without lube and cleaning with the 1.6 and it still functions on the suppressed setting without the can. my barrel is 10 inches, not 10.5 and I'm only shooting 556. I'll probably order a gas jet today, been procrastinating on that. |
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i do not know what size i have used for the last 3 years, but running drills a few weeks back i noticed how slow the gun recoils, and it was killing my split times. So I bought the kit to try to speed up the action
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Midwest and PMM have both been out of 1.3mm and 1.35mm jets for awhile now.
Anyone have a handle on some? |
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I did this exact thing, got a 1.3 jet put In my SCAR 17 13” Barrel and man it it feel amazingly better over all the others. Didn’t even try the 1.35
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I've been making my own gas jets for my 16" Scar 17S. I started with one I drilled with a #55 drill bit (1.32mm), and had good function over a few magazines of MEN, unsuppressed. Rifle would constantly malfunction if left in the suppressed setting without the suppressor, and worked fine with one. It used to work fine in the suppressed setting without a suppressor.
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I haven’t experienced any issue with my unsuppressed 16 or suppressed 17... should I mess with them?
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I'm running a 1.20mm gas jet on my 17 with 16 inch barrel and it runs suppressed and unsuppressed with or without the can on either setting. I was hoping I was going to be able to start to see it hiccup then go to the next size gas jet but haven't quite hit that point yet.
PMM said 1.20 was the lowest he would go. Has anyone seen similar instances with their 17? FWIW, running sdn6 suppressor. |
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Quoted:
I'm running a 1.20mm gas jet on my 17 with 16 inch barrel and it runs suppressed and unsuppressed with or without the can on either setting. I was hoping I was going to be able to start to see it hiccup then go to the next size gas jet but haven't quite hit that point yet. PMM said 1.20 was the lowest he would go. Has anyone seen similar instances with their 17? FWIW, running sdn6 suppressor. View Quote |
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Quoted: That does seem a bit small. My 17 has a 1.35mm gas jet and won't reliably cycle with CBC 168 smk once it gets dirty (set to suppressed with no can). With my surefire 762 mini 2 it runs fine, of course. View Quote |
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Quoted: Yeah I know. I started with 1.30, 1.35, and 1.40 gas jets hoping I would be able to choke it up. Didn't happen so got 1.20, and 1.25. Still no luck. I am running old 1980s surplus malaysian ammo. View Quote Unless you are going to use that ammo exclusively and have a ton of it, you might want to try some decent match ammo and see if it cycles. |
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so 1.3 is what we've decided is a good place to start with 13" scar17?
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Quoted:
I'm running a 1.20mm gas jet on my 17 with 16 inch barrel and it runs suppressed and unsuppressed with or without the can on either setting. I was hoping I was going to be able to start to see it hiccup then go to the next size gas jet but haven't quite hit that point yet. PMM said 1.20 was the lowest he would go. Has anyone seen similar instances with their 17? FWIW, running sdn6 suppressor. View Quote |
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I installed a factory 10” barrel in my SCAR16 sbr. Surefire 762 SOCOM RC. 62gr CBC fmj.
I foolishly ordered 1.65 as the largest gas jet. It locks the bolt back with gas valve set to unsuppressed without can installed and with can installed. It won’t lock the bolt back set to suppressed with the can attached. I ordered 1.7, 1.75, 1.8, 1.85 to try. |
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Stepped down to 1.40 with my 16" 17s, lets just say it's still over gassed. Going to try 1.35 next, which I have on hand. I may order 1.20, 1.25 and 1.30 just to see how this shakes out. Ended up with damn burr in my bolt carrier causing the bolt to drag and lock up.
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Quoted:
Stepped down to 1.40 with my 16" 17s, lets just say it's still over gassed. Going to try 1.35 next, which I have on hand. I may order 1.20, 1.25 and 1.30 just to see how this shakes out. Ended up with damn burr in my bolt carrier causing the bolt to drag and lock up. View Quote |
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Quoted: That's not good, that means your bolt carrier wasn't hardened correctly and will more than likely need to be replaced. Had a buddies do the same thing. Was cheaper to buy replacement bolt carrier than send to FN to fix. View Quote Being as I'm not one to assume anything, and I can actually repair things, I cut the burr out using ceramic hones and it's back to about 90% normal function and the bolt is no longer hanging up in the carrier. I need to do a little more work(or I may just keep shooting the shit out of it) and it will be back to 100%. I spoke with Jarrod Legsdin at PMM at length about this and it's not necessarily that the carrier is soft, but it's due to it being excessively over-gassed and causing excess wear at the cam pin slot. He has seen this happen multiple times and usually runs them until they explode, or the burr wears away on it's own. This rifle was bought in 11/2012, so we can presume it was either made in 2012 or late 2011. Whether they were having any kind of heat treating issues at that time is unknown. Also, I recall the heat treat issue relating to bolts, not carriers, but I could be wrong on this one. I also spoke with Todd Magee from Dead Air regarding this, because my primary concern is back pressure. He told me a little more about the FN 701 suppressor as how it is designed as he did some work with the FN engineers. It was a very interesting conversation. The FN 701 suppressor is a very rudimentary design see US Patent 8167084 - As he described it the FN suppressor is a very "flowy" design, therefore significantly lower back pressure, but loud. |
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Thought I'd add a little to this thread.
Awhile back I'd put a PMM 1.35 into my 16" 17S. Never had an issue but wanted to sit down and try some others in it as well as my 20" 17S. Ordered in fro PMM pairs of 1.25, 1.30 and another 1.35. Off to the indoor range today with a bunch of S.A. surplus. 16": Started with the 1.25. With the gas at full the gun ran fine, throwing brass at least 6 feet. Gas set to suppressed setting and no suppressor the rifle would not function. Suppressor attached, a TBAC Ultra 7, and the rifle functioned perfectly on the suppressed setting. I could tell a slight difference in felt recoil but the biggest thing I noticed was when suppressed I had far less gas than I've ever had in my face....was actually pleasant without glasses on. That's a big plus and makes the time and expenses worth it all. 20": Again I started with the 1.25. With gas at full the gun ran fine and threw brass about where the first rifle did. Set gas to suppressed mode and the gun still ran without any issues, no suppressor. In this mode the carrier''s reduced momentum was very noticeable as was the very reduced recoil. Added the suppressor, same one, and the gun still ran fine with a little increase in the recoil. I need to note that this gun actually has the TBAC muzzle brake on it so less recoil without the suppressor is normal, my 16" just has the TBAC flash hider. The reduced gas, just like my 16", was very noticeable with the suppressor on and I'm thrilled about that. The PMM gas jets are worth every cent to me. It's nice they are hex head vs the OEM flat head, makes experimenting so much easier. As the smallest jets I had were the 1.25 I couldn't go down any further but the results I had led me to think that was as far as I needed to. I love that the SCAR allows for this type of tuning, makes setting it up for my uses perfect. |
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I’ll add an update as well. Just dropped a 1.2 PMM gas jet into 16” 17S barrel, and it functions perfectly. Unsupressed setting without a supressor still throws casings and lock back on an empty mag. Does not function on a suppressed setting with out a suppressor. Throw on my SDN-6 though and it’s back to hammering rounds. Noticeably less recoil and gas to my face. I’m in love with my rifle all over again.
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Small data points to add
Setup: SCAR 16S with factory 10" barrel, Dead Air Sandman-S (With Dead Air brake), Hornady Black 75gr. SBR ammo With PMM 1.55 gas jet:
With PMM 1.30 gas jet:
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Just wanted to add, 1.35 with the same setup above had the same issues. 1.4 and 1.5 gas jets are next.
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Anyone have any data for the 16” 16S? Almost everything is for the 17S. Even trying to google comes up with data for the 17S with a 16” barrel.
Is the factory 16S setup fine from the factory? No changes needed? No one suppressing the 5.56? |
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SCAR 17 with factory 13" barrel, Surefire SOCOM 762 Mini 2
M118LR, set to suppressed 1.55 mm does not lock back on last round. 1.60 mm (stock gas jet) cycles perfectly. Fairly soft, minimal gas-to-face. Magtech CBC 168gr, set to suppressed 1.40 mm does not lock back on last round. 1.45 mm locks back on last round, but the bolt feels extremely slow, as if it just barely touches the end plate in the receiver. I am sticking with the stock gas jet. If you have a higher back pressure can you can probably use a smaller jet, though. |
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Quoted:
Anyone have any data for the 16” 16S? Almost everything is for the 17S. Even trying to google comes up with data for the 17S with a 16” barrel. Is the factory 16S setup fine from the factory? No changes needed? No one suppressing the 5.56? View Quote |
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Quoted:
My 16" 16s was massively overgassed from the factory. Slippers and I changed it to a smaller jet, but I don't recall the size (maybe he does) and it's a sbr with the 10" barrel installed. The gas jets are cheap. Just buy a bunch and start tinkering. They are super easy to swap. And which jet you use will depend on what can you're installing. Just buy some jets and start tinkering, it's fun. View Quote View All Quotes View All Quotes Quoted:
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Anyone have any data for the 16" 16S? Almost everything is for the 17S. Even trying to google comes up with data for the 17S with a 16" barrel. Is the factory 16S setup fine from the factory? No changes needed? No one suppressing the 5.56? |
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Quoted:
Getting the stock jet out of my 16 was not super easy. I finally got it with a modified easy out. View Quote |
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Did the barrel have a lot of rounds down the pipe? Mine had about 800 or so, all suppressed before swapping valves. A drop of ALG Go Juice (unbelievable carbon cutter by the way) left for a couple minutes, and the gas jet came out no problem. View Quote View All Quotes View All Quotes Quoted:
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Getting the stock jet out of my 16 was not super easy. I finally got it with a modified easy out. |
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For removing the stock gas jet this tight clearance bit from mcmaster is the exact size needed: https://www.mcmaster.com/5944a42
This is what we used on JoshNC's 16S, and I have used on my 17S 16" and 13" barrels. |
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Last Update with 1.4 and 1.5 Gas Jets
Setup: SCAR 16S with factory 10" barrel, Dead Air Sandman-S (With Dead Air brake), Hornady Black 75gr. SBR ammo With PMM 1.40 gas jet:
I should note, that standard 556 ammo worked 100% suppressed on the suppressed gas setting with the 1.4mm (IMI M193 & MEN M193). AE 223 55 gr and the TAP SBR ammo just doesn't have enough umph to fully cycle the round. The empty case will extract, but the carrier won't go back far enough to pickup the next round. With PMM 1.50 gas jet:
At this point, I'll settle with 1.50mm. Both TAP SBR and AE 223 functioned 100%. |
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Quoted:
Last Update with 1.4 and 1.5 Gas Jets Setup: SCAR 16S with factory 10" barrel, Dead Air Sandman-S (With Dead Air brake), Hornady Black 75gr. SBR ammo With PMM 1.40 gas jet:
I should note, that standard 556 ammo worked 100% suppressed on the suppressed gas setting with the 1.4mm (IMI M193 & MEN M193). AE 223 55 gr and the TAP SBR ammo just doesn't have enough umph to fully cycle the round. The empty case will extract, but the carrier won't go back far enough to pickup the next round. With PMM 1.50 gas jet:
At this point, I'll settle with 1.50mm. Both TAP SBR and AE 223 functioned 100%. View Quote |
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Got tired of buying jets that were not the sizes they were supposed to be.
Bought my own blank jets and went to work 10 inch scar 16, Federal m193 1.4 fail to pick up next round, normal gas setting perfect function suppressed in both gas settings 1.58 (1/16 drill bit) would fail to to lock back, 80 percent of the time. perfect function suppressed in both gas settings, can dump full mag suppressed and not die. 1.72 (#50 drill bit) perfect function, occasional fail to lock back in suppressed setting. perfect function suppressed on suppressed setting, very little gas to face, can still mag dump and not die. Been dealing with this gun for a while and could not get it to shoot suppressed, after 3 shots you would be hating your life. I have finally dialed it in and its gonna start getting more love now, and shot a whole lot more. |
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