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I was recently pursuing some info on something silencer-related, and came across a thread on either ar15.com or m4carbine.net that was largely argumentative. One thing in the thread that stood-out was someone declaring that PRI gas-buster charging handles were 100% snake oil. I have gas-busters in both of my most-used AR15s, and I had always felt that they certainly contributed to the fight against gas, however, I had never done a true side-by-side comparison. So, for the sake of entertaining this online shit-talker's claim, I brought a regular charging handle with me next time I shot, and swapped it in toward the end of my session.

The gas-buster absolutely works.

With the regular handle, I was stinging halfway through the benchmark string of fire I use in evaluating stuff lately. That's not the case typically. I then immediately swapped the buster back in, shot again, and was able to keep my eyes wide open and on target for the duration.

Of course it's always possible that his setup somehow didn't allow the buster to shine, which is totally possible. They are certainly not snake oil parts though, for anyone considering one.

Another thing I think folks should seriously consider for their suppressed ARs is adjustable carriers. I use them in both of the above-mentioned guns. The big names are Gemtech and Bootleg. Gemtech has two settings, and Bootleg has four. The Gemtech comes as a stand-alone carrier, and the bootleg is a complete BCG. They work by allowing gas to vent out of the carrier BEHIND the gas rings when the bolt is locked, thus delaying unlocking and getting rid of some extra gas and fouling through the ejection port, that would otherwise be dumped into the receiver.

Neither of my guns have adjustable gas blocks, and these carriers help them run better. I have nothing against adjustable blocks, but I think something can be said for getting gas out of the bore, and routing it to the atmosphere in a way that minimizes filth in the gun, as opposed to limiting gas escaping the bore, just to have it spill back into the gun when the bolt opens.

Springs and buffers also come into play, and are a first effort for many, in tuning an AR15 for use with a silencer. Different guns call for different equipment. One of mine is an LE surplus Colt 933 upper, with a potentially somewhat eroded gas port. This gun uses a Gemtech carrier with a .308 carbine spring and H2 buffer. It will run with and without a silencer, so long as I adjust the carrier. This gun typically runs a bit cleaner inside than my other one, but has a heavier recoil impulse. The other is a 10" barrel that was cut down from a 16". This gun has a smaller gas port as a result, relatively speaking. This gun has a direct-thread can on it, and isn't used without a silencer. I employ an adjustable carrier, regular carbine spring, and unmarked light buffer in this gun. It has a lighter recoil impulse, and is easier to shoot fast with, but is dirtier. It will not work reliably if I increase spring strength or buffer weight.

I am in the midst of building a gun with a Superlative Arms piston system, and am certainly eager to see how it compares, when used with a silencer. It will be my first piston AR, and was appealing to me because of their "bleed off" system, which I think is advantageous when using a silencer. We'll see.

What do other silencer users on sigforum do to optimize their guns, if anything?

This message has been edited. Last edited by: KSGM,
 
Posts: 316 | Location: Northeast GA | Registered: February 15, 2021Reply With QuoteReport This Post
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I am new to suppressor's. Am running a .30 cal YHM Resonator on my 16" middy with the YHM mini muzzle brake mount.
I have a BM A2 Lower and my upper is a PSA Freedom.
I have not modified the set up in any way other than replacing the muzzle device.
Have not shot it a lot. But what I have shot has functioned 100% and have not noticed excessive guess being an issue. But have not done any rapid fire testing either.
I am looking to learn more as I want to expand my shooting in the future.
I have an AR10 set up I want to move into at some point.
The buster charging handle sounds like an easy way to enhance the experience. Thanks for the heads up.
I will stay tuned.



"Practice like you want to play in the game"
 
Posts: 16415 | Registered: September 21, 2005Reply With QuoteReport This Post
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AR10 rifles have a bad reputation, when it comes to silencers. I had one that could not get through two rounds without a malfunction due to carrier speed. I got another carrier for it, and ported it in the correct location. Gun runs like a top. Of course that carrier is for dedicated suppressed use, and will likely not function without a silencer attached. I use a direct-thread can on it anyway, so it doesn't bother me.
 
Posts: 316 | Location: Northeast GA | Registered: February 15, 2021Reply With QuoteReport This Post
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I prefer to buy barrels with moderate or tight gas ports to avoid needing adjustable items. Having the rifle run reliably both suppressed and unsuppressed, with no setting changes, with the widest range of ammo is the ideal for sure.

However, proper tuning is a function of:
  • Cartridge - powder and projectile
  • Barrel length
  • Dwell time (barrel length after the gas port)
  • Gas port size
  • Gas system efficiency (how many leaks along the way)
  • Buffer and spring (A5, Rifle, Carbine, and the myriad of options for each) as it relates to lock delay
  • Suppressor back pressure, which can effectively increase dwell time

    There are certain "recipes" about buffer and spring combinations with particular barrels, but changing any of those factors changes how the bread is made and makes the easy button no longer work. Wanting a rifle to perform equally well with M855 NATO and Tula .223 requires a compromise somewhere. Personally I just don't shoot weak .223 through the rifles I've setup to run NATO ammo with or without a can.

    In my opinion having something adjustable is a shortcut unless your objective includes tuning the gun for some miniscule performance gains. The exchange is added failure points, added maintenance, and therefore decreased reliability. Not to say they're not nice to just get something working that otherwise won't, but the reality is you're probably working with one or more ingredients that are off and you just aren't aware (most commonly huge gas ports so cheap guns will run a wide range of ammo at the price of beating themselves to death).

    As for gas to the face? Yeah, having some captured pressure in the system when the bolt unlocks will result in additional gas being dumped back in the system. The higher the velocity of that gas the higher chance it has to make it back to the charging handle and get you feeling like it's the last scene in Old Yeller. Something like a carbine-length gas system on a 16" barrel with a suppressor added on has all kinds of dwell time, higher port pressure leading to higher gas velocity, and a high potential to dump gas back on itself. Using a K-can or something designed for less back pressure on a midlength 12.5" or 13.7" is going to be an improvement out of the gate. Having a more-advantageous setup might lead someone to think a gasbuster isn't doing work. Similarly, having a very terrible setup might also make a gasbuster look like it's completely ineffective because there is just SO MUCH coming back at you.

    Another tip: RTV gasket material can be added to the charging handle to create a better seal and push more gas out of the ejection port and other bleed locations (receiver gaps, receiver extension, magwell) and make the user shooting experience a little better.
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    Posts: 5941 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
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    Heck yeah, Rustpot! Thanks for the awesome contribution.

    In my experience, when it comes to all the factors you mentioned (which are certainly on-the-money), a silencer just acts different than as many inches of barrel would, when it comes to how gas works. If I was to take identical 16" guns, and cut one down, in order to add as many inches worth of silencer back to it, the silencer gun would still be far dirtier than the original, and would likely have other adverse silencer effects as well. Friggen weird how it works. I reckon the gasses trapped in the silencer during consecutive shots causes these effects.

    As stated in my OP, I prioritize silenced performance, as opposed to function with and without a silencer, so that factors into my thought process always.
     
    Posts: 316 | Location: Northeast GA | Registered: February 15, 2021Reply With QuoteReport This Post
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    quote:
    Originally posted by KSGM:
    Heck yeah, Rustpot! Thanks for the awesome contribution.

    In my experience, when it comes to all the factors you mentioned (which are certainly on-the-money), a silencer just acts different than as many inches of barrel would, when it comes to how gas works. If I was to take identical 16" guns, and cut one down, in order to add as many inches worth of silencer back to it, the silencer gun would still be far dirtier than the original, and would likely have other adverse silencer effects as well. Friggen weird how it works. I reckon the gasses trapped in the silencer during consecutive shots causes these effects.

    As stated in my OP, I prioritize silenced performance, as opposed to function with and without a silencer, so that factors into my thought process always.


    Think of the system in terms of pressure and flow and the suppressor behavior makes more sense. You're adding an expansion chamber to slow down the gasses, which means you're now holding onto gas and creating a scenario in which the time with positive pressure in the gun's gas system is extended. It doesn't behave the same as more barrel because the barrel has relatively low volume compared to a can, and once the bullet exits the barrel you're now un-corked and can freely flow out the end instead of being purposefully slowed/trapped.

    The effective lengthening of dwell time relates more to unlocking timing/forces and carrier speed/gas impulse, which drives the gas port size selection for your particular combination. This is why a 10.5" Mk18 and a 14.5" M4 have drastically different gas ports when everything except dwell time is equal, and why a suppressor might dictate or allow a smaller port for either.

    This is also one of the drives behind other BCG changes companies have made. For instance; LMT has added gas vents in the carrier body to help get the gas out, it also has a revised cam-track in the carrier to force more carrier motion before unlocking, thereby delaying unlocking and allowing gas pressures to drop further before an already-accelerated carrier strips the bolt from the barrel and unlocks the user end of the gas system. This is the E-BCG from them, which has a few other changes not related to this conversation as well. There are other examples, this is just one.
     
    Posts: 5941 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
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    I have one of the LMT E-BCGs that you mentioned. It is more-or-less waiting on a it's parent gun at the moment. My prior use with it was in an 18" LMT MRP, and it was one of the most unpleasant rifles I'd ever shot with a silencer attached, in terms of the gas-in-the-face aspect. I am a believer in the E-BCG design features, but it certainly didn't help in that particular instance, with that particular aspect of suppressed firing. I have always considered trying it in one of the guns mentioned in my OP, but have always doubted that it would have more of a positive effect than the vented carriers I use in them already, considering the rear vent in the E-BCG is smaller, and my previous experience with it was as bad as it was. I figure there's no way the modified cam path can make up for the smaller vent. I could be wrong.
     
    Posts: 316 | Location: Northeast GA | Registered: February 15, 2021Reply With QuoteReport This Post
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    A question for you, Rustpot: How might a PRI fatboy gas tube play into these silencer scenarios? It is advertised as reducing carrier speed and cyclic rate in M4 carbines by giving a carbine-length tube the volume of a rifle-length. I have one in my 11.5" 933, but was never able to do any side-by-side comparisons, and it's hard to judge effectiveness of one component when there are so many others in play as well.
     
    Posts: 316 | Location: Northeast GA | Registered: February 15, 2021Reply With QuoteReport This Post
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    Whether or not one part matters depends greatly on the other parts. As mentioned with the gasbuster charging handle, any single component can function phenomenally or fall on its face depending on the mix of parts, ammo being fired, even the amount of lube in some cases.

    As to the PRI fat boy gas tube - I assume it's a product thrown into the market to help combat the issues with carbine gas systems. There's been a desire from military units to build a better mousetrap since the rifle was made - that's how we get to flat top receivers, mlok freefloat rails, and all the other doo-dads that are out there.

    The rifle was designed and optimized as a 20" rifle, with rifle-length gas system, and a rifle buffer and spring. This is the softest, most consistent, most reliable iteration of the military M16/M4 in all its varied flavors over the years. Shortening the gas system and shortening the receiver extension for a carbine ultimately works to counter reliability. So it's not surprising that someone was trying to replicate *some* aspect of the rifle system and graft it onto the carbine. Heck, the A5 buffer system was born from this same type of rifle-meets-carbine endeavor, and I'd say that's a pretty good thing.

    Since the gas port is much further back in the barrel on a carbine-length gas setup the port sees a much higher pressure than it does in a rifle-length setup. This translates to faster gas as it expands into and down the gas tube. Faster gas into the BCG expansion chamber makes for a faster, more violent cycle of the BCG+bolt, etc. (which is why heavier buffers are a very common recommendation). So the thought is to bring that gas velocity down. Why not replicate the rifle gas system volume? That seems to work better, right?! Except you're now at a higher port pressure with a different orifice, feeding a different overall volume of gas into the action. And the PRI tube needs to be standard diameter at the ends right? Or else it won't enter the gas block or gas key. So you have a center section of tube that works to reduce gas velocity by creating an expansion chamber. This deviates greatly from the intended design, and you're now working with compressible fluids (gases) that are changing velocity a few times within the tube (fast at the block, slow in the middle, fast again at the key). I don't have specific knowledge of the PRI tube, mind you, but I would suspect it would foul internally quite a bit over time, as the self-cleaning aspect of high velocity gas is mitigated with an expanded center section. But if you're then restricted won't it be back to having fast gas and potentially self-clear? Perhaps, I would add gas-path-inspection to your BCG if you aren't already - for this reason and others.

    All of that to say: will it work? I don't know, probably, depends on what else you've got going on. It would probably make a properly functioning 10.3" Mk18 with crane spec port and sprinco blue/H2 into a non-working gun. If you've got serious gas issues it might be the ticket, which like I mentioned is a very common thing if your maker doesn't want to get into this aspect of ARs or wants to ensure reliability over the widest range of ammo and isn't very concerned with longevity. Big ports, light buffers, and everything in between doesn't really matter.
     
    Posts: 5941 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
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