DI vs Piston in a suppressed SBR

jbgleason

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I have a registered SBR lower and am planning to put together an upper for it strictly as my home defense rifle. As it turns out, I have two identical 11.5" barreled flat top uppers on hand. They are identical except one is DI and one is a short stroke piston set up. As they sit, they have old school handguards and no optics. So I need to select one or the other to build out in order to prepare it for its intended use.

I plan on leaving my SureFire Micro can on the rifle full time as well.

I have heard of reliability issues with barrels less than 14.5" in DI but this upper shoots fine although I haven't shot it with the can yet.

So is there any particular reason to select one operating system over the other for this particular mission?

Thanks in advance for your responses.
 

lowlight

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    Re: DI vs Piston in a suppressed SBR

    The shorter the barrel the more you want to go with a Piston.

    The DI will get really dirty, really fast. The extreme nature of the blowback can lead to function problems. As well it is going to blowback harder towards you the shooter. The Piston will help reduce the potential for problems.
     

    callen3615

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    Re: DI vs Piston in a suppressed SBR

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">

    The DI will get really dirty, really fast. </div></div>

    Especially suppressed.
     

    VKC

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    Re: DI vs Piston in a suppressed SBR

    If you are getting a can, go with piston...it runs much cleaner and thus is more reliable.
     

    jbgleason

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    Re: DI vs Piston in a suppressed SBR

    I understand the issue with carbon build up and getting dirty but this particular rifle isn't going to be shot very much. Hopefully never really. I get plenty of time on my other AR's and, once I know this one functions correctly, I plan to clean it thoroughly and leave it be.

    That being said, I am interested in LL's comment regarding the blowback. Would it be safe to say that I am going to see less unburnt powder/gases/oil coming back in my face with the piston? Given the intended use of this rifle, I probably won't be wearing pants much less eye pro if I am shooting it. So that would be a concern for me. I didn't really consider that before.
     

    lowlight

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    Re: DI vs Piston in a suppressed SBR

    Yes, even with a basic gas buster charging handle you're going to catch a lot of powder in the face if you go with a short barrel DI and a suppressor. I have gas busters on my SBRs and with the cans they push plenty in your eyes to make it a bit uncomfortable. Especially initially.

    The piston saves your a lot of that because the gas is expelled at the connection of the piston so it doesn't make it back to your face like with a DI gun. Difference better expelling the gas under the handguard versus out the back towards the shooter.
     

    jbgleason

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    Re: DI vs Piston in a suppressed SBR

    Great. Decision is made. Build out the piston upper. Thanks for the insight.

    Now what to do with the 11.5" DI upper? Will have to ponder that.
     

    lowlight

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    Re: DI vs Piston in a suppressed SBR

    Put a Krink on the 11.5" and consider playing with that. Or I think Adams makes a retro fit package to change it to a piston. <span style="font-style: italic">(I know someone make a retro fit kit, forget who)</span>
     

    rsilvers

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    Re: DI vs Piston in a suppressed SBR

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vkc</div><div class="ubbcode-body">If you are getting a can, go with piston...it runs much cleaner and thus is more reliable. </div></div>

    Not with a suppressor - they both get dirty. The particles com through the bore - just as they do with a suppressed MP5.
     

    Chucky

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    Re: DI vs Piston in a suppressed SBR

    I agree with rsilvers. I shoot a lot of suppressed fire and I run a 10.5 LWRC suppressed the majority of the time. While the system does run cleaner when you throw a suppressor on it still gets very dirty. Lube is your friend and will allow you to shoot a lot suppressed with either system. I have put at least 2K rounds through a 14.5 LMT I have and the only thing I did was add lube and I didn't have one malfunction with it.

    I wouldn't get hung up on you absolutely need a piston. If you want one get it. They are nice but they have there downfalls also. They bleed the gas usually where your forward shooting hand is so it seems to me they get hotter quicker and also they breath a little fire at night when they are venting the gas. All my left handed shooting gloves are cooked on my piston guns.
     

    jakhamr81

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    Re: DI vs Piston in a suppressed SBR

    If you are shooting suppressed a piston system will not buy you anything. Some even say that they are slightly louder than a DI system. The empty brass is being ejected under pressure, that is why the case comes out black. If anything, go with an adjustable gas block so you can slow down the cyclic rate. Even LWRC understands that this is key to shooting suppressed.

    Read more at these links:

    http://noveskerifleworks.com/switchblock/

    http://www.defensereview.com/noveske-rif...rview-part-one/

    Also, there is nothing wrong with a suppressed DI SBR. The MK18s are DI and they seem to be working just fine for the military; even with a suppressor.
     

    Jig Stick

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    Im bringing this thread back from the dead. LOL

    Has there been any progress made in this area? Im getting ready to build out a stripped Bushmaster AR lower into an SBR to run suppressed. I was set on a BCM 10in upper, but now Im wondering if a piston setup wouldnt be better. I DO NOT like getting gas and shit in my eyes. What are my options for buying a short barreled piston upper?
     

    MarkCO

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    If you go search, you can find some interviews/articles from John Noveske where he agrees with Brian and disagrees with Frank. There are several factors to consider...if you are getting a barrel that you can spec with an undersized gas port and can tune/open based on your suppressor and load, that is the absolute best route. It will result in the least amount of wear in the gas system and the least amount of gas in your face. A PRI gas-Buster or a BCM mod4 CH is nice as a safety feature, but it is really all about set-up. If you want to be able to run suppressed and un-suppressed, the best solution is still to set up the gun for suppressed with that load and then with the suppressor off, match a load to that set-up for 100% function. Changing carrier and buffer might even get you there if you don't want to change loads. Third best is an adjustable gas system. I have built and run identical guns sans the Piston v. DI, and after running them and shooting them, I sold the Piston kits.

    The VAST majority of consumer grade ARs are overgassed. When you go to the pistol length gas system, gas blocks (especially adjustable gas block) and gas rings take a beating. The gas is almost double the pressure and temperature as compared to a rifle length gas system. Put in 30% too much gas...sure you are going to have issues. But if you know how to set them up, it is not that hard.

    I think you will be better off with DI than PD in the long run.
     

    Jig Stick

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    Where would I look to get a barrel with an undersized gas block? Who makes a short barreled piston upper? My googlefu is failing me again
     

    Cobracutter

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    If you go search, you can find some interviews/articles from John Noveske where he agrees with Brian and disagrees with Frank. There are several factors to consider...if you are getting a barrel that you can spec with an undersized gas port and can tune/open based on your suppressor and load, that is the absolute best route. It will result in the least amount of wear in the gas system and the least amount of gas in your face. A PRI gas-Buster or a BCM mod4 CH is nice as a safety feature, but it is really all about set-up. If you want to be able to run suppressed and un-suppressed, the best solution is still to set up the gun for suppressed with that load and then with the suppressor off, match a load to that set-up for 100% function. Changing carrier and buffer might even get you there if you don't want to change loads. Third best is an adjustable gas system. I have built and run identical guns sans the Piston v. DI, and after running them and shooting them, I sold the Piston kits.

    The VAST majority of consumer grade ARs are overgassed. When you go to the pistol length gas system, gas blocks (especially adjustable gas block) and gas rings take a beating. The gas is almost double the pressure and temperature as compared to a rifle length gas system. Put in 30% too much gas...sure you are going to have issues. But if you know how to set them up, it is not that hard.

    I think you will be better off with DI than PD in the long run.

    Couldn't have said it better myself. Quality of a the commerical piston uppers is still not on the level of DD/Colt/KAC/Noveske. The Noveske Switchblock is an awsome barrel/gad block combo for running cans. Otherwise you are stuck with a massivley overgassed system suppressed or a gun that won't cycle with the can off.
     

    Cobracutter

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    Where would I look to get a barrel with an undersized gas block? Who makes a short barreled piston upper? My googlefu is failing me again

    Adam Arms makes a decent upper with adjustable gas block. Not sure how they hold up to heavy use however.

    Its the gas port size that matters. Years ago, shorty uppers were kind of an experiment. Now, Companies have figured out the gas systems and gas ports to get the 10.3/10.5/11.5 systems very reliable. DD, LMT, BCM and KAC all make fantastic SBR uppers.
     

    MarkCO

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    Where would I look to get a barrel with an undersized gas block? Who makes a short barreled piston upper? My googlefu is failing me again

    I have been using SI Defense barrels. I ordered mine with 0.035" ports, basically a pilot hole to get me started. You can always go to Green Mountain barrels and buy a blank, they are under $100, some like $50. For about $200 you can get it profiled threaded and headspaced set up exaclty like you want. ADCO may be able to help you out too.
     

    Jig Stick

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    Barf.com seems to be pushing this new product: MicroMOA - Home of the Govnah - Modular Adjustable Gas Block

    Will this thing fit under the Daniel Defense handguard that that comes on the BCM upper im looking at? This Micromoa product seems like a good idea.

    http://micromoa.com/
     

    Shooter0311

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    I have a govnah under a geissele mk1 rail and have had no issues suppressed or unsuppresed. It is on a legion 14.5 inch 5.56.
     

    JJones75

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    I had a 10.5" LWRC and it ran great with a can , I have since sold it in order to buy a 10.5" Noveske with a switch block and I could not be happier. This gun does not see the high volume of fire between cleaning that a military battle rifle might , but I have put 800-1000 rounds through it in classes with no cleaning and it still functioned fine and that is running a suppressor the whole time. I very very rarely shoot this gun unsuppressed. Yes it does get more gas in the face even with a gas buster charging handel but only when the gas block it not adjusted to the suppressor setting , when adjusted its no worse than any conventional 16" AR with or without a can..
    That said , run the piston upper with the can then build a 7.5" 300 Blackout on the other upper.
     

    MicroMOA

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    I have a govnah under a geissele mk1 rail and have had no issues suppressed or unsuppresed. It is on a legion 14.5 inch 5.56.

    Thanks for the post!

    A new article just came out last week on our gas block..it is a two part article

    The article below discusses the use of an optimal unsuppressed mode since just about every barrel out there is over gassed to handle cheap ammo. So unlike the other tool less options out there that give you just full gas when un-suppressed, the Govnah gives you the option to have an optimal un-suppressed mode and then you have an adverse mode which matches the port in your barrel.

    Part 1
    MicroMOA?s ?Govnah? Adjustable Gas Block (Pt 1 of 2) - RECOIL
    Part 2
    MicroMOA?s ?Govnah? Adjustable Gas Block (Pt 2 of 2) - RECOIL

    Our patented, modular, tool-less, adjustable gas block was specifically designed to handle heavy full auto suppressed usage.
    It is currently the only tool less adjustable gas block on the market that uses a standard unmodified gas tube.
    With this design, you can adjust the regulator plate when hot and just use a bullet tip to move the plate. In addition, you can feel the plate in complete darkness to know what position it is set to by feel.

    Merrill-Govnah-Regulator-Plate-Adjustment-618x412.jpg


    You can see that the Govnah is based on actual port sizes from NO port to whatever you want to drill. In the event that your barrel is overgassed and you don't want to run suppressed, I personally would have 1 port match your barrel's gas port which would be your adverse position (for use when dirty or using weak ammo) and you would also use that to install/align the block for installation then work your way up like you would on the baby Govnah to a port size that locks your bolt back on the other port.

    Or go with a 3 position if you want a position for a suppressor as well.

    Merrill-Govnah-regulator-plates-top-left-clockwise-2-position-custom-and-3-position-custom-2-540x412.jpg
     

    Chucky

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    If you want to build an upper the best adjustable gas block in my opinion is the Syrac. It is fully adjustable with a detent pin so you don't have to worry about the screw coming loose. The only issue with the Syrac which isn't an issue for me is that it is only a 1 position gas block but you can fully tune it for gun. I know plenty of guys who run the Syrac also on their 3 gun rifles because they can dial the gas way down to make the rifle shoot a little softer.

    My LWRC 10 inch gun had an insane amount of ammo through it mostly suppressed and I cannot think of one malfunction I had with it. I gave it to a buddy to do a demo also and he put over 3K rounds through it in one weekend without a single malfunction. It definitely still gets dirty suppressed but with FireClean it cleans right up and stays wet for quite sometime before I have to relube.
     

    cssnider1

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    I've got a 300 blackout with an 8.2" barrel from Ice Arms. It's got an adjustable gas block, DI piston length gas system, and suppressed. I mainly shoot subsonic with this setup as I have a 16" blackout that I shoot my supers in. I agree with what they said above, the best way to go shooting subs suppressed it pistol length, DI, adjustable gas block. That way you can adjust the pressures to shoot you. Right now I'm shooting hand loaded 220gr Sierra Match Kings, have the gas block set just right, with a JP silent capture buffer, and I NEVER take anything to the face or eyes. It cycles perfectly when it's shooting about 950FPS.....and it's dead on at 100yds. I have no reason to shoot farther than that on my SBR
     

    MarkCO

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    The other issue with the Syrac is leakage. On a Rifle length system, it is not a huge deal. On pistol length, leakage is a more significant problem.
     

    Fenix Mike

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    Im going to go through this shortly (only been 9 months, guess the ATF is at a year now) and one of the guns will be a SBR with a factory Mk18 upper. I had considered selling it to get a Sig 516 10 inch upper, and was torn on whether to get a AAC 8.5 inch 300 AAC upper or build one on a piston setup, guess we will see how the other guns run. This is my only SBR right now, but with the speed of the E-file stuff I may do a Sig 716 12 inch AR and just do a Sig 516 10 inch anyway. I love how the Mk18 shoots unsuppressed though so im hoping its just as reliable with the SDN-6.