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Thread: Barrel Question for a new project ;17" rifle gas barrel

  1. #1
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    Barrel Question for a new project ;17" rifle gas barrel

    I am going to have a 20" barrel cut down to 17", probably by ADCO, and i need to be consulted on my options. I want a lighter weight barrel profile, with government being more than fine.

    The barrel will be free floated under a Troy trx 15"rail and a syrac adjustable gas block will also be implemented.

    Low weight and durability are my primary concerns, with accuracy following those.

    Barrels i have considered so far:

    BCM 20" CL'd government

    BCM 18" SS SPR rifle gas

    FNH 20" CHF CL'd government

    Rainier Arms ultra match 18" SS rifle gas

    Noveske is more than I'm willing to spend. The spr profile barrels would need to be reprofiled to reduce weight, adding cost. I do not require the accuracy of stainless, but I'm not adverse to using a high quality stainless barrel. This is going to be for a project upper that i will chronicle here on the forum. A 17" rifle gas barrel running a very light A5 buffer in my current lower.

    I think i would prefer the smaller gas port of the 20" barrels, but since the syrac will allow me to adjust gas at the port, this is not critical. I'll likely use a std BCM bcg.

    From my research the FNH and the BCM 20" gov profile barrel have .091" gas ports. If i had my pick, i wood prefer a gas port smaller than .100.

    So, my brothers, here is where you can help: places to buy these barrels, qualities of one barrel type that make it superior to another, tips on barrel crowns/angles, hand guards, pinning vs set screw on the gas block, etc.

    Most of my shooting with this upper will be with an aimpoint, offhand. My goal is ultimate smoothness in a combat carbine upper. Think uses such as run-n-gun, three gun, CQB, etc. I want a handy setup.

    I am soliciting any and all advice that helps me achieve my stated goals. Anybody who attempts to tell me that the setup will not function, please don't waste your time posting in my thread....because you can kiss my ass.

    Wes at MSTN had verified that this general setup works.

    Alright, go!

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  2. #2
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    Since you really don't want real opinions why bother posting this? Can you at least articulate why either an 18" or 16" won't work for you?



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  3. #3
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    Gunz, on the contrary i would like on topic opinions.

    I am drawn to the rifle gas system, so absent getting a custom gas port drilled in a blank, this seems to rule out a 16", correct?

    What effects would a rather drastic reprofiling of an SPR profile 18" barrel have on longevity and accuracy on a stainless barrel?

    Sent from my SPH-D710 using Tapatalk 2
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  4. #4
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    Quote Originally Posted by Iraqgunz View Post
    Since you really don't want real opinions why bother posting this? Can you at least articulate why either an 18" or 16" won't work for you?
    The 17" rifle gas setup has the shortest dwell time of any rifle gas barrel I've seen. I want to have a setup that will allow me to adjust the gas coming into the carrier while still using a std carrier. I want to experiment with reducing gas pressure at the source (gas block/gas port), as opposed to using an enhanced carrier from LMT.

    Sent from my SPH-D710 using Tapatalk 2
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  5. #5
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    I am not a barrel maker so I can't answer that. But, unless I am mistaken (and I could be) SPR barrels have a port size of around .099 in order for the to cycle 100%.

    I have never seen a 17" barrel. I just can't imagine that you cannot get an 18" SPR barrel, add something like the Vltor A5 with a good spring and buffer and the gun wouldn't be smooth shooting.

    It's kind of like getting a 14.5" barrel permed to save the little gain that you get. When I do a side by side in class people usually say "Wow I can't believe all the headache for that".

    Quote Originally Posted by BufordTJustice View Post
    Gunz, on the contrary i would like on topic opinions.

    I am drawn to the rifle gas system, so absent getting a custom gas port drilled in a blank, this seems to rule out a 16", correct?

    What effects would a rather drastic reprofiling of an SPR profile 18" barrel have on longevity and accuracy on a stainless barrel?

    Sent from my SPH-D710 using Tapatalk 2



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

    Semper Paratus Arms AR15 Armorer Course http://www.semperparatusarms.com/cou...-registration/

    M4C Misc. Training and Course Announcements- http://www.m4carbine.net/forumdisplay.php?f=141

    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

  6. #6
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    Hi!

    I can help with a few of your concerns.

    In regards to clamp vs set screw on your gas block, it's a choice depending on your concerns. Benchrest accuracy nuts will tell you to do a clamp; this is because a set screw is claimed by some to cause a slight deformation on the inside of the barrel, thereby decreasing accuracy. However, set screw is more secure I think, so it's a trade-off between slightly better accuracy or slightly better reliability. I'd say the whole thing is splitting hairs, but personally on my AR15 I'm getting a clamp.

    Also, have you considered getting a lightened bolt carrier by JP? Reduces the recoil impulse and also generally *the* carrier to use with an adjustable block. Also, since 17" is kinda cutting it close for reliability, a lighter carrier lets you get away with less dwell time and all that.

    For Handguards, you might be interested in an AP Custom carbon fiber tube. They have dull CF available so you have a choice of no shiny CF if you'd like. This differs from other carbon fiber handguards in that it does *NOT* use adhesives and instead uses a mechanical attachment to the standard barrel nut like any other metal handguard out there. The vents serve as attachment points for rails, and you can have him do the vents/attachment points at 12, 3, 6, 9 o'clock so it's like any other modular rail.

    This is what a AP Custom tube, dull CF, with a top rail running across the top looks like:
    http://www.boomershooter.com/forums/...ndguard-rails/

    Weight for the 15" *without* a rail running across the top is 6.5oz. Then you add 1.3oz for the nut for a total 7.8oz. The rail I linked is a bit heavier at 9.2oz + 1.3oz= 10.5oz.

    Carbon fiber also is good at rejecting heat so it doesn't heat up quite as quickly as a metal handguard.


    Also, in regards to barrels:

    For rifling type, cut rifling is the best period, but very expensive. The usual choice for benchresters. See Krieger or Bartlein. Button rifled is slightly less accurate. Vendors include Noveske, BCM, Lothar Walther, Shilen, Lilja... and a bunch of others.

    In regards to barrel lining, chrome lining increases barrel life but decreases the accuracy of the barrel. A non-lined barrel like a bare SS barrel is going to be more accurate but good for less rounds. There's a new barrel treatment called meloniting/nitriding that, from my research, apparently increases barrel life just like chrome lining does but *does not* decrease accuracy since it's a surface treatment rather than a coating. However, note that SS doesn't take too well to meloniting (I think; correct me if I'm wrong), and that generally Chrome Moly barrels are the best material to be melonited I believe.

    So basically, out of your picks, BCM SS or Rainier SS are going to be the most accurate. Rainier's Shilen blanks are very good, but I've heard (not entirely sure) that BCM's SS blanks are from Krieger's Criterion brand, which I'd say is just as good and might be better... so I'd get the BCM personally.



    However, just my input on the whole 17" rifle gas thing. Most 3gunner's I've seen go for an 18" when they want to do rifle gas. If you want to do 16", you can do an intermediate length gas tube; it's in between mid length and rifle. There's not really a set intermediate; KAC has their own length and Noveske at one time seemed to have an intermediate as well and it's a different length than KAC. You'd have to have a custom gas port location though, as you mentioned.

  7. #7
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    SPR gas ports are .104".

    I have an FN 17" M16A2 barrel with .093" port. It functions reliably so far but cycles slowly with 223 ammo. With my M4S is cycles smartly and sounds like a .22 pistol.

  8. #8
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    Why don't you just buy a barrel that fits what you really want? IE a rifle gas 18" barrel that is in the kind of profile you want? Also, 17" is too short for reliability w/rifle-gas, the same way that a mid-length is finicky with a 14.5".

    What you need is a 18" rifle-gas barrel that is medium profile. Don't even mess with reprofiling if you can get a barrel that works out of the box. All of the SPR profiles (BCM, Rainier Arms, etc) are quite heavy and not the best choice for "run & gun." There are several good choices available. Nordic Components makes an outstanding barrel in this configuration, and Criterion offers one like this as well but chrome-lined. Both would fulfill your needs well.

    I myself have a Nordic 18" on my 3 gun rifle. Coupled with a comp, it is ultra flat shooting and pretty light too. Did I mentioned sub-MOA too?

  9. #9
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    Quote Originally Posted by Iraqgunz View Post
    I am not a barrel maker so I can't answer that. But, unless I am mistaken (and I could be) SPR barrels have a port size of around .099 in order for the to cycle 100%.

    I have never seen a 17" barrel. I just can't imagine that you cannot get an 18" SPR barrel, add something like the Vltor A5 with a good spring and buffer and the gun wouldn't be smooth shooting.

    It's kind of like getting a 14.5" barrel permed to save the little gain that you get. When I do a side by side in class people usually say "Wow I can't believe all the headache for that".
    I agree that its not an issue of the 18" not working well enough. All of the quality setups I've used have worked 100%. This is a lot of trouble for little gain..but at least there is no muzzle device issue.

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  10. #10
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    Quote Originally Posted by RyanB View Post
    SPR gas ports are .104".

    I have an FN 17" M16A2 barrel with .093" port. It functions reliably so far but cycles slowly with 223 ammo. With my M4S is cycles smartly and sounds like a .22 pistol.
    Thank you, Ryan. It seems i need a larger gas port and should use the gas block to tune the system.

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