10.5 inch Barrels in 5.56: Gas system length, twist rates, etc.

Welcome aboard, a lot of your considerations were the same I had. Went with a 10.5” 1:9, with a can, it has the maneuverability of a 16” gun, just makes a lot less noise. Mine is nothing fancy, just the basics, a tool for specific tasks.



I have played with 7.5” without suppressors and they are pretty ridiculous, fun but I make sure I am plugged like I am shooting an open pistol from retention.

My 300 blk is shorter but it uses faster powders and the can I use on it is longer, so it’s about the same OAL anyway.

First welcome to THR, we’re glad to have you! Pleasantries dispensed with, it sounds like you’re working through everything nicely so far. I don’t have a bunch of experience on the matter but I have assembled both 7.5” and 10.5” variants for specific potential uses.

Obviously the 7.5” required a pistol length system so I chose a completed Aero upper with 1:7 twist 5.56, nitrided barrel, low pro gas block, standard weight M16 BCG, and an H2 buffer. It’s just a hair over gassed but not bad. I ordered an H3 to test it with and had 2 failures running it clean and dry (for testing) so I swapped back to H2 and kept it that way.

It sees a steady diet of 55gr soft point and accuracy has been within my ability with a red dot to 200 yards. It’s loud and fun and some of that noise is mitigated by a linear comp which does have a downside: it shoots fireballs. Now given the purpose of a close range maneuverable “pistol” I don’t expect muzzle signature to be a real problem.

I had enough fun with that one to think I might like another, slightly longer version which I built using another 5.56 1:7 twist with a JP adjustable gas block. Very soft recoil considering. Alas someone wanted it more than me and money talked. That lead to another 10.5” and, if all goes well, the postman will deliver tomorrow what I need to finish it up.

My recommendation would be either a 10.5” or 11.5” carbine gas, nitride treated, 5.56 with adjustable gas block and an H2. I would also suggest picking and sticking with a muzzle device before ordering a handguard and choosing one long enough to shroud it if there are no side firing ports. My current 10.5” will use a 13” free float and a KVP Magnum which should leave about a 1/2” sticking out of the front for me, a few inches more if it gets a suppressor down the road.

I have used the SBA3 brace to date but ordered the SBM4 for the new build and I think I’m going to like it even better. If however I decide on an SBR stamp I’ll swap out for a standard carbine extension.


Current status of my 10.5” with KVP 3 1/4” Magnum linear comp sitting alongside my daughter’s fixed position mini-stock 16” pencil middy with A2. As is evident, component choices will dictate overall length.


AGB and carbine gas tube for the 10.5”.


Close up of Kaw Valley Precision standard linear comp and magnum. 2 1/4” and 3 1/4” respectively.


My 7 1/2” with Magnum linear comp. The complete upper came with a 8” iirc handguard.


Another of my daughters shooting her Aero 16” middy with the KVP Magnum.

I did 8.5” Wylde. It was painfully loud and not particularly enjoyable.

The truck with gas systems is more in dwell than it is in anything else I think (opinion, can be argued sensibly to be pressure). The gas system works off of pressurized gas that flows through the port and gas block, through the tube and the blast of gas shoves the bolt backwards. It doesn’t necessarily work like a hammer, but it also doesn’t necessarily work like a hydraulic ram either. With shorter dwell the gas impulse is very short which is what leads to a lot of reliability issues in super short ARs. For 10” I would still be looking for a pistol length, knowing good and well that it is likely overpassed, but would be using an adjustable gas block to reduce the gas flow a bit and correct that situation. Carbine works, but based solely upon dwell time I would not think it to be reliable enough for me.

10.5” pistol length AGB 1:7” stainless H2 - that’s where my money went.

I built mine with a 10.5" 1:7 twist pistol gassed upper with the standard H2 buffer.

It ran great, ate everything from wolf to NATO ammo. Fireballs were bigger than my 16-18" guns but nothing compared to my 3" comped 500mag!

10.5" 1:7 was/is the standard in SOF for the MK18 upper. The first ones had a full heavy profile, the later DD ones have a lighter profile. We fired everything from 55 grain M193 to 77 grain MK 262. My personal favorite for a short(er) barrel is a 11.5" 1:9. I fire the same range of projectile weights through it too. Unless you have an old "legacy" A1 type barrel with something like a 1:12, I have found the twist rate conundrum to be a myth.

g3ops said:

I am worried about excessive fireballs, loudness, concussion, and recoil. . .

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You should worry more. My 10" 5.56 is so loud I'm embarrassed to shoot it when others are on the rifle range. It's obscene, way worse than a .30 bore with a brake.

. . .and that's with the flash can.

That aside, accuracy of this basic PSA barrel is perfectly acceptable to me. Running fixed iron sights, it's minute of man to 300, perfect for a no-stamp PDW.

@edwardware that picture is disturbing! Mine is also a screenshot and not nearly so BBQesque. I do like that you own a portable flame thrower/projectile launcher combo though.

I'm one who feels the rifle (barrel length) and caliber/cartridge (powder, burn rate) are generally designed to be symbiotic. I know tons of people build AR's with a <10" barrel, but I don't see the point. That being said, I wouldn't personally go lower than 11.5" for many of the reasons (and pictures!) listed above.

7" twist seems best on shorties., A sound moderator which directs all blast downrange like the Kaws or better a Noveske Flaming Pig or even the Russian Krinkov (which are surprisingly good) type are an excellent idea. The adjustable gas block is almost a must if going to use suppressed . Pistol length gas tube works OK but I prefer the Carbine length on my 10.5" barrels reserving the pistol gas for .300 BO shorter barrels. Using at least a Heavy buffer in them helps I use the Spikes Spyder Tungsten one that is between H1 & H2 in weight with good luck and a standard carbine spring and full auto bolt . 10.5" barrels are not that problematic these days in a well executed build. They were the "Commando" length of choice from the factory for a long time .

The other consideration not yet mentioned is barrel manufacturer and their port size. I throttled the AGB on the Ballistic Advantage 10.5” carbine a fair amount. I expect the same to be true of my SOLGW 10.5” carbine based on gas port. If a manufacturer is too conservative with sizing there’s potential for a finicky eater in a shorter barrel/carbine gas vs same length pistol gas.

SI’s Gridlok is nearly a pound without the inserts which is rather portly imo, particularly in its price range. I mention this since adding a suppressor down the road, if you do, will have you slinging a lot of weight around with what is generally built to be a very heavy pistol but lighter weight AR.

By comparison the Aero Precision rail I used in the first 10.5” was about 13 oz with barrel nut. The Phase 5 13” rail being delivered today is even lighter. Adding a heavy linear comp or suppressor was always a part of my long term plan. Having started with a hybrid comp/brake on a 16” had me wanting no part of them thereafter (for what I do).

I do like the SBA3 but the 4 feels stiffer by comparison. I had planned to order an SBA4 for a carbine extension but swapped last minute for the SBM4 and a pistol extension.

g3ops said:

I'm working on a new AR pistol build and need some help.

Click to expand...

If you give a man a fish, you feed him for a day

FISH
Buy this kit-
https://palmettostatearmory.com/psa...sba3-pistol-kit-with-nibr-bcg-5165449540.html

and this lower-
https://palmettostatearmory.com/psa-stealth-lower.html

Buy them now before they go out of stock.

You'll also want to get a Colt extractor spring and an H2 buffer and install them.

If you teach a man how to fish, you'll feed him for life

LEARNING TO FISH
Basics
The 5.56 is the easy button. It's the most economical to shoot, easy to find and we know what it takes to make it work in a shorty AR.

Barrel
In 5.56, 10.5" to 12.5" are good choices. It's easy to get them to run reliably and give enough velocity for good terminal performance with most ammo. The 10.5 is the minimum most experienced AR shooters recommend. After shooting a 10.5" and 11.5", I found I prefer the performance of the 11.5. Any barrel of these lengths will get you to 300 yards or more.

All ARs between 10.5" and 12.5" are going to be loud and concussive. Best way to eliminate that is use a suppressor. Next best way is a linear comp. If you're going to use a big and heavy linear comp and/or start adding blast shields, you might as well go all in and get a suppressor. The BRT Covert Comp is small, light, affordable and does a good job sending the concussion down range. It doesn't eliminate flash as well as a flash suppressor, but it doesn't throw big fireballs when used on shorter barrels.

Gas System
The carbine gas system works very well in these lengths. Port pressure in a pistol system is much higher than a carbine gas system and the higher the port pressure, the more critical gas port tolerances become. The carbine gas system is a better length when using drop in handguards. The MagPul Slimline handguard is a good choice for the money. They offer good heat protection and give the shooter a little more room when shooting. Free float handguards give more options for length, but they cost more and are not as much an advantage for precision as they are with longer barrels. This is strictly a personal choice.

About Dwell Time- Dwell time, the time the bullet is in the bore doesn't matter. The gas system doesn't reach operating pressure until the bullet has exited the bore. The difference in time between the two systems is measured in less than a micro second. What matters is blow down time. Blow down time is how long it takes the pressure at the gas port to drop below operating levels after the bullet exits the muzzle. Gas operated firearms operate on the pressure that's in the bore after the bullet leaves the barrel.

You only need to concern yourself with three buffers. H2, A5H2 and Rifle. The H2 weighs about 4.6 ozs and is what the M4A1 is issued with. It uses a carbine spring and carbine receiver extension. H buffers at 3.8 ozs is fine, but a little on the light side. Carbine buffers are about 3 ozs and are just too light. Recoil with carbine buffers in short barreled ARs is much sharper than necessary and uncomfortable.

The A5H2 buffer weighs about 5.3 ozs. It's longer than the H2 buffer and needs an A5 style receiver extension to accommodate that extra length. The buffer is longer to allow the use of a rifle length action spring. When tested by the military, it was found to improve reliability of the AR by a small amount. I prefer the A5H2 RE assembly over the carbine RE. However, switching from a carbine RE assembly to an A5 assembly is a refining something that already works great.

For myself, I like the extra length of the A5 RE when using the SBA3 pistol brace.

Rifle buffers are about 5 ozs and use a rifle length receiver extension & spring. It'll take some minor modification to work with a pistol brace.

If an AR isn't gassed correctly, changing buffer weight won't fix it. An over gassed AR with a heavy buffer is still over gassed. An under gassed AR with a buffer that's too light will have sharp recoil and feel like it's under gassed.

A heavier buffer will not reduce recoil. But it can soften it.

Twist
Twist does not stabilize the bullet. RPM does. RPM is the result of twist rate and velocity. Short version is more RPM is needed to stabilize long bullets than short bullets. (Bullet weight has little to do with it.) As short barrels give less velocity than long barrels, bullets from short barrels will have less RPMs than bullets from long barrels of the same twist. Twists slower than 1:7 can work in shorter barrels, but may not work as well, especially at extended ranges. There's no question that 1:7 does. Short barrels in 1:7 are much easier to source than other twists. Why put in the extra work looking for a barrel with a twist rate that's not as efficient?

Barrel Profile
Barrel profile has little to do with the gas cycle. If you want a light profile barrel, get one. It'll reach higher temperatures with fewer rounds, but the shorter can control that with a slower rate of fire. If a heavier barrel is wanted, know that the profile around the chamber and a few inches ahead of it is most important for controlling heat. If you shoot enough to wear out the barrel, congratulations! You'll have achieved a feat few shooters have matched. When that happens replace the barrel and go back to shooting. The experience will make you a better shooter.

Barrel Materials
Don't over think this one. Yes, a chrome lined 4150CMV barrel should take longer to wear out than a stainless steel barrel, but so what? Get a quality barrel and shoot it. Shoot it until you're ankle deep in empty cases. You'll have more fun doing that than getting stuck in Analysis Paralysis.

Barrel Lining
Again, don't worry about it. Barrel quality is more important than lining. A quality unlined barrel is better than a cheap chrome lined barrel. Be reasonable about it. Unless you're going use top quality ammo, don't bother getting a barrel with pin point precision. A precision barrel won't shoot tight groups using econo blaster ammo.

Extractor Spring
Few AR makers use a top quality spring. As a result, many extractor springs wear out quickly or are marginal at best. You'll save yourself a lot of headaches if you get a Colt or Sprinco M4 extractor spring and install it as soon as practical. If the AR stovepipes or an empty gets jammed in the action, the extractor spring needs to be replaced immediately.

Over Gassing
It's always better to start with the right gas port but if it's too large, there's an easy fix. The BRT EZ Tune gas tube. Affordable and easy to install. Answer the questions about your configuration when ordering and BRT will send you the right gas tube.

Skylerbone said:

First welcome to THR, we’re glad to have you! Pleasantries dispensed with, it sounds like you’re working through everything nicely so far. I don’t have a bunch of experience on the matter but I have assembled both 7.5” and 10.5” variants for specific potential uses.

Obviously the 7.5” required a pistol length system so I chose a completed Aero upper with 1:7 twist 5.56, nitrided barrel, low pro gas block, standard weight M16 BCG, and an H2 buffer. It’s just a hair over gassed but not bad. I ordered an H3 to test it with and had 2 failures running it clean and dry (for testing) so I swapped back to H2 and kept it that way.

It sees a steady diet of 55gr soft point and accuracy has been within my ability with a red dot to 200 yards. It’s loud and fun and some of that noise is mitigated by a linear comp which does have a downside: it shoots fireballs. Now given the purpose of a close range maneuverable “pistol” I don’t expect muzzle signature to be a real problem.

I had enough fun with that one to think I might like another, slightly longer version which I built using another 5.56 1:7 twist with a JP adjustable gas block. Very soft recoil considering. Alas someone wanted it more than me and money talked. That lead to another 10.5” and, if all goes well, the postman will deliver tomorrow what I need to finish it up.

My recommendation would be either a 10.5” or 11.5” carbine gas, nitride treated, 5.56 with adjustable gas block and an H2. I would also suggest picking and sticking with a muzzle device before ordering a handguard and choosing one long enough to shroud it if there are no side firing ports. My current 10.5” will use a 13” free float and a KVP Magnum which should leave about a 1/2” sticking out of the front for me, a few inches more if it gets a suppressor down the road.

I have used the SBA3 brace to date but ordered the SBM4 for the new build and I think I’m going to like it even better. If however I decide on an SBR stamp I’ll swap out for a standard carbine extension.


Current status of my 10.5” with KVP 3 1/4” Magnum linear comp sitting alongside my daughter’s fixed position mini-stock 16” pencil middy with A2. As is evident, component choices will dictate overall length.
View attachment 941253

AGB and carbine gas tube for the 10.5”.
View attachment 941249

Close up of Kaw Valley Precision standard linear comp and magnum. 2 1/4” and 3 1/4” respectively.
View attachment 941251

My 7 1/2” with Magnum linear comp. The complete upper cane with a 8” iirc handguard.
View attachment 941252

Another of my daughters shooting her Aero 16” middy with the KVP Magnum.
View attachment 941250

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I always liked that 7.5 you snap a pic up every now and then... I wouldnt be opposed to building a clone of yours... nice build bruv

g3ops said:

Also, more importantly, I was worried about losing too much velocity in shorter barrels, and from what I have been reading, 10.5 is probably the shortest I would go and still be able to maintain near the 2500 fps range to have at least a good chance of the bullet fragmenting on impact - I would like to have good stopping power, not just to poke holes. 10.5 still dramatically increases maneuverability and reduces weight. Do any of you have some experience that would help with my reasoning here?

Click to expand...

So, I'll just parrot back what we were discussing in another thread. Using heavier grain projectiles in shorter barrels actually works favorably in the case of 5.56, especially 69gr, 75gr, and 77gr. Typically with 55gr ball you want to maintain at least 2500fps for reliable fragmentation. In the case of the Mk262 77gr SMK, it was designed to perform and inflict alot of damage well below the 2500fps mark. While you may not be able to burn up pallets of the stuff without going bankrupt, keeping a few magazines dedicated for SD wouldnt be out of order, 55gr ball ammo for general plinking and of course not discounted for SD either....

I would also second skylerbone's advice in terms of a 1:7, nitride bbl. I would also go with a 10.5 bbl with a 3 prong hider in favor of keeping your pistol compact and maneuverable and also to keep from going blind in low light. I have found that my blast can on my 10.5 doesnt do much for me, except make my 10.5 slightly longer and slightly less maneuverable than my 11.5 that doesnt have a blast can. Right now my 11.5 has an A2 BC and it isnt as obnoxiously loud as some might have you think, at least that's my opinion. I'd ditch a blast can and go with a 10.5 with decent flash hider. Nice compact no nonsense pistol.

Mine are range fun and home defense. If it’s dark out you can be sure there’s 1,000 lumens switched on before I touch the trigger so muzzle flash isn’t really much match. At least that’s my reasoning for the linear comp. The 7.5” can slip into my weekend duffle or my day pack if need be.


Got parts in today finally and finished up. The HEX extension and SBM make for a longer combo but I was going for a look with this one.

About five years ago, Palmetto had a sale on 12" uppers so I went that route and put a Sig brace on it. Then braces became questionable so I took it apart and lost interest in it. A couple years ago my son built a 10.5" setup based on Palmetto parts and I regained interest in the 12". Side by side comparison, I like the 12" better.

Noise and recoil is a touch less, and velocity is noticeably higher- when shooting steel with 55 FMJ loads at 150 yards, you can hear the difference in the time of flight based on how long it takes for the steel to ring. I should shoot them over a chrono and see what the actual difference is.

I am in the same boat, building an AR pistol. Finding parts at reasonable prices is a PITA. Also leaning in the 5.56 8-10.5" barrel length range with the ability to add a can later. From what I have seen from videos online and pistol builds at the range, the right muzzle device will make or break shooting a short barrel AR pistol. That is where most of the part research comes in. Fortunately, since most AR barrels are 1/2 x 28 thread pitch, there are plenty of options. Right now I am leaning towards the Thumper but my favorites change on a whim with more articles I read.

https://www.rainierarms.com/battle-arms-thumper-muzzle-device-22cal-1-2x28/?avad=260373_b1ce2044d

That was an excellent high level summary. Well done.

I would like to know more about this:

MistWolf said:

About Dwell Time- Dwell time, the time the bullet is in the bore doesn't matter. The gas system doesn't reach operating pressure until the bullet has exited the bore. . .
Gas operated firearms operate on the pressure that's in the bore after the bullet leaves the barrel.

Click to expand...

I do not recall seeing this in the literature. My understanding is that gas system pressure equalizes (with barrel pressure) nearly instantaneously when the bullet clears the port.

The piston (whether an AR bolt, AK piston, M1 op rod, etc) doesn't move very far until the bullet's long gone, but all of the kinetic energy to be had is stored in the reciprocating parts as momentum before the bullet uncorks the muzzle.

So, citation please?

Wow... a lot of very helpful, and articulate info in this thread.

I am going to compress my opinions. ( lol )

5.56 over 223 Wylde... many very good ammo choices are full power 5.56.. and I won't want to have an possible issue from a well heated barrel.

Gas system length... no pistol length in 5.56... carbine length minimum... and consider a Adj. GB or properly sized gas port from the get go.

1n7 Twist...1n9 is "fine" ... 1n7 is mo' better. Or 1n8 twist... a very good choice.

Barrel Profile / length... my preferred barrel profile is something like the Criterion Core, ( precision choice ) Or a BCM Enhanced LtWt. CL ( durable barrels ), both 11.5" minimum.
Those profiles, offer weight and balance improvements. IMHO, a great compromise over a "pencil" profile - USGI type profile.
Dimple the barrel at the gas block set screws.

12.5" gets a decent velocity boast. ( https://www.ar15.com/forums/ar-15/S...-10-5-11-5-12-5-and-14-5-ALL-DONE-/16-714088/ )

A good barrel manufacturer will offer quality steel / SS choices.
Don't skimp on the barrel... it is the last place the bullet see's from your firearm.

Chrome lined barrels offer many advantages.. durable, more resistant to rust, and easier to "maintain" given a less then perfect maintenance schedule... ( end of the world stuff... your time is better spent making sure you and your loved ones are safe... opposed to "I better make sure the barrel is oiled."
And given the current cost of ammo... a $100 dollar more expensive barrel is a HUGE bargain. You might spend a hundred bucks on ammo trying to make a less expensive barrel shoot to your expectations.

Muzzle device.... First, consider a quality flash hider....the 5.56 is more pleasant to shoot with a brake / comp.... but given the shorter barrel... Hiding the muzzle flash is more important than recoil reduction.
Effective Flash hiders don't need to cost a lot.... even the "lowly" YankeeHill closed tine is very effect... and available for $15 bucks. ( Also it will work with a Griff. Armament Gen II QD blast shield )

Consider a QD blast shield / Muzzle brake combo. Many QD blast shields are a great compromise... however, they are expensive.
If you don't have the funds for a QD blast shield / Muzzle device.... I would buy a forward directing muzzle device... BUT.. they tend to "amplify" muzzle flash.
FWIW....Some are QD blast shields are proprietary, IE... require the same brand muzzle device and QD blast shield. ( Lantac, Surefire, Gemtech )

I could go on and on about QD blast shields.... some are very simple to attach, some are kind of fussy to attach.. some mount very snuggly, some loosely ( adversely effecting accuracy )... some allow the use of many brand muzzle devices... some when heated up , are complete PITA to remove at a moments notice.

I guess.... all QD blast shields have merits and faults. I will gladly answer questions about specific brands I have used. ( Lantac Gen I & II, Surefire, Frefrans, Griffin Armament , Gemtech )

Another comment about muzzle devices... I prefer to keep them as short as possible... extended cans aren't for me ( and certainly no offense to those using them, it is your firearm )... So food for thought.... If I were to add length to a AR15 platform, I would prefer added barrel length ... for the additional velocity.

As for your Strike Industries Muzzle devices... Check out the "Oppressor"

edwardware said:

That was an excellent high level summary. Well done.

I would like to know more about this:

I do not recall seeing this in the literature. My understanding is that gas system pressure equalizes (with barrel pressure) nearly instantaneously when the bullet clears the port.

The piston (whether an AR bolt, AK piston, M1 op rod, etc) doesn't move very far until the bullet's long gone, but all of the kinetic energy to be had is stored in the reciprocating parts as momentum before the bullet uncorks the muzzle.

So, citation please?

Click to expand...

Critical Thinking Time: If the gas system filled and operated the action in the fraction of a micro second it took the bullet to travel from gas port to muzzle, dwell time wouldn't matter at all. That's because the system would be filled when the bullet reached the same distance from the port every time. In a carbine gas 14.5 inch barrel, the distance from gas port to muzzle is 7 inches. That means the system would have to get fully charged before the bullet travels that distance. That means if that distance were extended to 20 inches, the system would still reach operating pressure before the bullet travelled 7 inches. Therefore, the pressure in the bore when the bullet is at that point would always be the same regardless of distance from port to muzzle and whether or not a suppressor was installed

Yet, adding barrel length beyond the gas port or a suppressor increases gas pressure to the system. We have to ask ourselves, why? Because adding length or adding a suppressor increases the time it takes for the bore to blow down to ambient pressure after the bullet uncorks the muzzle. If that change affects operation of the gas system, it means the gas system is being affected after the bullet leaves the muzzle. That means the system runs off the pressure left in the barrel after the bullet uncorks the muzzle.

The Army released a study where they found the bullet has exited the bore and traveled several feet down range before the system pressurizes and activates the action of the Garand and the M14. If anything, the system of the M14 would likely pressurize before the bullet exits because the piston is right there at the gas port. The gas in a carbine system AR has to travel roughly 10 inches before it reaches the expansion chamber and piston.

If that's not enough, take time to look up and study slow motion video of gas driven rifles. They show clearly the bullet exits the muzzle before the action even begins to move. You can also study just how long it takes the gas in the gas in the bore to vent after the bullets departs.

There are many advantages to having a self loading firearm operate on residual pressure. Smoother operation, improved extraction and waiting to unseal the chamber after most of the gases have vented at the muzzle is safer for the shooter.

I built a bunch of AR pistols over the last 20+ years. I consider a 10" barrel minimal Except in the case of my ultimate and most reliable and overall "sweet" sample that is based on a Noveske Diplomat PISTOL lower I had around when the "brace" ruling first surfaced. I also had a most unusual "gas trap" 9.5" ARMs Tech Compak 16 upper I got from a Navy special ops guy (no I won't use what unit) in a trade for a pre 64 Win M70 30-06 . He was given that upper to try out in action and he liked it but eventually went to a SIG format . He had the Arms Tech Compact 16 "laying around" so ... Here is what the magic part of the system looks like :
and I got it with the Smith flash hider pictured which indeed is the best flash hider - ever IMHO.
The upper is literally hand built and has an in house built heavy stainless barrel with a GAIN TWIST 9.5" stainless polygon rifled barrel which does stabilize the 77 bullet very well, is exceedingly accurate and gets a litlle more velocity than the usual 10" barrel does with the Military loads I tested . I run the gun with the Arms tech Bolt it came with which has Colt markings on the carrier group and use top quality service parts over the years to refurbish it. ..The upper came with one of the first railed hand guards a Predator quad rail and a Gas Buster charge handle. I took the Noveske Flaming Pig off the 7.5" Diplomat upper and put it on the Arms Tech upper , The Diplomat lower came with an H2 Buffer and a pistol tube so I put an SB Brace on it when they first became available. I run an Aim Point M4 on it with a top quality offset sight system. It is my go to SD weapon but truthfully stays in a safe unless I feel the need, which today in Oregon is quite frequently. . It is a MOA gun with a 2 MOA Reddot, plenty good for 200+ yards and short and light and completely reliable.
You won't get another one these days

@Gordon sooo much nice going on there!

edwardware said:

You should worry more. My 10" 5.56 is so loud I'm embarrassed to shoot it when others are on the rifle range. It's obscene, way worse than a .30 bore with a brake.

. . .and that's with the flash can.

That aside, accuracy of this basic PSA barrel is perfectly acceptable to me. Running fixed iron sights, it's minute of man to 300, perfect for a no-stamp PDW.

Click to expand...

My 7.5" is like that but my 10.5" has very little muzzle flash. Next I'll do a 12.5".