Optimized Suppressed Upper build

[mtdawg169]

Hello gents, I've been a member here for a good while, but never very active on WEVO. I'm looking to change that, so I thought I'd kick it off with a new build thread. I initially posted this on a local forum where the average member is less technically savvy than the average WEVO member, so please forgive any parts that may seem rudimentary.

These days, there are all sorts of products and gadgets out there to help deal with shooting suppressed (technically over gassing). Adjustable gas blocks ("AGB"), adjustable carriers, the WAR upper, even adjustable gas keys to replace the standard versions. The primary reason we have seen the introduction of these products is because the introduction of a suppressor increases gas flow and overall pressure within the system. This increased pressure can cause functional issues & excess gas ejected from the receiver.

To me, none of these solutions are really ideal. (blasphemy, I know) Most of them involve the addition of small set screws, detents, etc that quite frankly, I just don't trust. Sure, they work. But I'd just prefer a more simplistic solution. Adjustable carriers and gas keys came along as a drop in solution for folks that didn't want to screw around with the gas block. Or feasibly, something you could install and adjust without disassembling the upper.

Adjustable parts exist primarily for one reason. Too damn many companies are producing barrels with huge gas ports. That's fine if you're shooting unsuppressed and like to shoot weak steel case ammo. However, introduce full power ammo and a suppressor and you may have functional issues from over gassing or the dreaded "gas face".

Regarding the use of adjustable parts, one of the things I've always felt was that while they work, reducing gas flow at a location other than the gas port, was not ideal. It works, but realistically, all we're doing is putting a band aid on the real issue - a hogged out GP.

What do I mean by oversized? Well, when I run something like my BCM or KAC uppers with a suppressor, they are reliable, gas isn't too terrible and recoil impulse is smooth. Comparatively, alot of guns would require a heavier buffer to achieve the same feel and would still dump a lot of gas in your face. My buddy's MK18 will choke you out with his specwar attached. While DD makes a fine weapon, the commercial version of the MK18 uses a larger port than the one they build for the military. Why? So people don't complain that it won't run weak ammo. Downside? Harsh recoil and tons of gas with a suppressor attached.

So what's the best solution for someone who wants to shoot suppressed, most if not all of the time? The better solution is ultimately, a smaller gas port, reducing the gas flow at the source. Problem? No one offers them specifically sized for suppressor use, ever. I've known a few guys that had connections with companies like Noveske that were able to custom order a barrel for this purpose and spec out their own gas port size. But for the masses, it just hasn't been an option. Most manufacturers don't want to bother with them because the market for a reduced gas port ("RGP") barrel is fairly narrow. It's not for your average shooter.

Well, Sionics Weapon Systems in AZ is now offering a reduced gas port barrel in limited numbers. SIONICS has just released what I've been wanting for a long time. An 11.5 reduced gas port barrel, that is quality made throughout. It's currently on pre-order, so I should have it in a few weeks. And it is designed primarily for suppressed use. Per Sionics, it's for "suppressed use only" but set up correctly, can be used reliably without the suppressor too. This means, the gas port has been sized on the ragged edge of small. And that's a good thing for me. It's small enough to work reliably, but not so small that it can't serve double duty.
Pros: reduced gas and recoil.
Cons: possible ammo sensitivity during unsuppressed use.



http://sionicsweaponsystems.com/stor...-stripped.html

Barrel specs:
These Barrels are designed for use with a suppressor. We do not recommend using them without a suppressor as the weapon may not cycle properly.

These will be Limited production runs and only a handful will be available at a time. Availability will be intermittent.

SIONICS Barrels are manufactured from CMV 4150 Ordnance Steel. All Barrels are Radiograph and MPI tested.

Features:

11595E CMV 4150 Steel
M4 Barrel Extension
5.56mm NATO Chamber
1/7 Twist Rate
.750 Gas Block
Chrome Lined Chamber and Bore
SIONICS Designed Medium Contour
Manganese Phosphate Finish
Standard 1/2X28 Muzzle Threading
Carbine Gas System
X-Rayed and MP Inspected
Barrel Weight - 1 lb. 7 oz.

Build plans
Sionics 11.5 RGP barrel
BCM4 upper receiver
BCM KMR-A rail - 10"
LMT enhanced carrier (Gen 4)
BCM bolt
Standard BCM gas block
Upper will be mounted on a lower already equipped with a Vltor A5 buffer system.

I'm already very acquainted with the LMT enhanced carrier and Vltor A5 buffer system. Both are well proven additions, especially for suppressed use. My goals for this build are as follows:

Reduced weight vs my current 11.5 upper
Reliable function with / without suppressor
No adjustment or buffer swaps necessary
Minimal recoil / smooth impulse
Less gas face

Will it be the ultimate suppressed upper build? I guess we'll see. But I'm looking forward to it in a big way.

A little more info from Sionics Master Armorer.

Just to add some additional information to this. The first batch of barrels was done for a specific client (local SWAT) that wanted to replace their Über-heavy 11.5" piston guns. The goal was to trim weight, reduce gassing and maintain reliability with their duty ammo. They also stated that these would only be used with suppressors and the likelihood of shooting without one was very slim. However, we wanted to ensure that they would run un-suppressed in an emergency.


Once we had the basics down we then used a variety of port sizes and conducted testing with several types of ammo and buffer combinations. The end result was a suppressed SBR that would cycle and function with a wide variety of ammunition, and utilize standard components (no adjustable gas block).

[mtdawg169]

Build list:

BCM4 upper receiver
BCM KMR Alpha - 10"
BCM gas block and tube
Sionics RGP 11.5 barrel

Already on hand:

LMT enhanced carrier
BCM bolt, cam pin, firing pin, etc
BCM Gunfighter charging handle
Magpul MBUS Pro sights
Aimpoint T1 w/ Bobro mount
BCM KAG
Surefire Mini Scout on a KAC keymod mount

All riding on a Form 1 BCM lower with Geissele SSA trigger and Vltor A5 buffer system. This thing is going to be sweet.

Just one thing missing...

[Silencer Shop]

Very interesting. Keep us updated as you progress on this.

[mtdawg169]

Will do. The barrels should be finished soon, so I'll update once I get it together and again after I get it to the range.

[DutyUse]

Should make for a nice host. I've been piecing together an almost identical build, been on the fence about the sionics barrel though

[mtdawg169]

Should make for a nice host. I've been piecing together an almost identical build, been on the fence about the sionics barrel though

What barrel are you considering?

My current 11.5 upper is a KAC SR16 barreled upper (Christmas Cheer barrel) with a URX 3.1. It's a bit heavy and I've been thinking about putting together a lighter upper for a while. The Sionics barrel offering was enough to push me over the edge and set one up with a KMR-A.

[DutyUse]

What barrel are you considering?

My current 11.5 upper is a KAC SR16 barreled upper (Christmas Cheer barrel) with a URX 3.1. It's a bit heavy and I've been thinking about putting together a lighter upper for a while. The Sionics barrel offering was enough to push me over the edge and set one up with a KMR-A.

Planned on using this BCM 11.5 bfh barrel that's been kicking around with 10" kmr and BCM upper. I've had it for ages but I knew it would be a suppressed only upper so I've been researching how to cut down on the gas

[mtdawg169]

Planned on using this BCM 11.5 bfh barrel that's been kicking around with 10" kmr and BCM upper. I've had it for ages but I knew it would be a suppressed only upper so I've been researching how to cut down on the gas

I was seriously considering using their ELW barrel initially. Have you given any thought to using the Black River Tactical inserts?

ETA: not cool, sneaking those Fathom Spade carriers into the background!

[DutyUse]

I was seriously considering using their ELW barrel initially. Have you given any thought to using the Black River Tactical inserts?

Honestly I hadn't considered it. How permeant is the modification? A suppresser friendly upper like the Noveske switchblock has been more and more appealing to me lately

[mtdawg169]

Honestly I hadn't considered it. How permeant is the modification? A suppresser friendly upper like the Noveske switchblock has been more and more appealing to me lately

It's basically a set screw with a precision port. Available in numerous sizes. I think each set includes a range of three sizes. You just thread the inside of the gas block, screw in the insert and reinstall. Clint at BRT can help you decide on the appropriate sizes before you order. I think he even offers a pinable GB with the inserts for $55. You just try the different sizes until you find the one that works best. Once you've settled on the appropriate size, you never touch it again. Obviously, some experimentation is involved on the front end, but once it's done, you just roll on. If you ever want to take it out, just pull the block and remove it.

Pic from BRT website


http://www.blackrivertactical.com/co...tune-gas-port/

[DutyUse]

Thanks for posting brother, I really appreciate the write up and knowledge. It sounds pretty cool, but I think just putting the BCM barrel back in the safe and getting a sionics rgp barrel might be the way to go on this one

[mtdawg169]

Thanks for posting brother, I really appreciate the write up and knowledge. It sounds pretty cool, but I think just putting the BCM barrel back in the safe and getting a sionics rgp barrel might be the way to go on this one

That was my thinking. The port isn't stupid small though. I believe it's around 0.070. But don't quote me on that. It will still run without a suppressor. But I suspect it may be a bit ammo sensitive. When I get mine set up, I'll be running some different ammo through it to see where the limits are.

[mtdawg169]

This thread probably sounds like an advertisement. For the record, I'm not affiliated with BRT, Sionics or any other company. And I do not work in the industry in any capacity.

[alamo5000]

I read the initial post but not all the replies yet...

Since I have gotten a suppressor and have been shooting it on various things I have learned a few things.

Long story short I don't know if simply changing the port sizing is going to have the benefits you are after. It's sheer physics.

As others know I am pretty frickin' nerdy on a lot of things...

I am not trying to rain on any parades but I will explain why I think what I think. Maybe it will help with your process, maybe not.

Your ammo creates the most important factor which is PSI. The actual PSI (not CUP or anything else) will be the best measurement to use. PSI is what propels your bullet forward... and backpressure from a can on the barrel happens primarily in your bore, not your gas tube. Shorter barrels have a substantially greater PSI at the bullet exit hence a much louder 'boom' ...as the guys at Griffin put it, 'you decork' at a much higher PSI... whereas with a longer barrel those gasses are almost spent and hence the suppressor can more efficiently handle that decorking of that gas better. 11.5" inches is a whole different animal than say 18" inches... the total inner volume of the bore of each is substantially different.

The whole gas in the face thing is again not caused by porting of the barrel. It's caused by gas being trapped under extreme pressures in small containers, IE the bore of the gun....basically if you don't want gas in your face use a longer barrel and/or a more efficient suppressor that will help dissipate those gases more. To be 'perfect' the suppressor would probably have to be physically bigger IE have a bigger volume and a means to manage those gases.

When you shoot suppressed look at your spent cases, your mags, and your upper and lower... all that carbon comes from the back pressures in the bore itself, not from the gas tube depositing it backwards...if you look at the proportional size of a gas port to a .224 size bore there is no comparison... gas will take the path of least resistance.

Although this post was originally intended to be about noise it also applies to pressure and back pressure too... take a look at one of my old threads so you can see what I mean...

http://www.weaponevolution.com/forum...ise&highlight=

On a 10.5 barrel you have about 11,500 PSI at bullet exit... on a 16" barrel it's already down to just over 7,000 PSI... there is just simply more volume to deal with...

Also the nature of the gas has changed too. On a short barrel the gas is still in explosive expansion stage and on a longer barrel the gas has already expended a lot more of it's energy...

Hence this overall picture kind of tells the story (at least to me)...that the shorter the barrel the higher the pressure. The longer the barrel the less the pressure. One will have more gas in the face because of that bore pressure and one will have less gas in the face because of the same thing.

[DutyUse]

I really wish they made the same barrel but in 10.3" for a shorter overall package.

As much business as I've given Noveske I should try and call them and see if they would cut me a custom gas port