All Around AR

[No Bananas]

I have two AR SBRs, and now I'm wanting to round it out with a do everything 16" AR:cool:. For accuracy I'm gonna go with the BCM SS barrel and grab a decent 1/1.5-4/6x scope. Because it's a do everything I need to not only to make it accurate, but I also need it super-reliable. I'd like to run this one through tough courses and such.

One of my SBRs is an AA Piston and the other DI. Both have been equally reliable, no issues. The difference w/ the AA is it is A LOT cleaner, and the recoil is noticeably softer. The AA Gas block is hefty and adds noticeable weight and only works with a handful of FF rails. It also has an adjustable gas system for a suppressor if I ever got one. I have to admit that the piston thing is a bit of peace of mind in terms of reliability. Also, the bolt stays cool, which I've been told will lengthen the life of the bolt. True???

[USMC03]

When talking about accuracy several things need to be considered:

-Size of the target

-Type of ammo (match vs. ball)

-Distance

-Accuracy expectations

-Type of shooting you will be doing (ie. all prone shooting at static targets, running and gunning and shooting from unconventional positions, etc.)


There is a difference between "mechanical accuracy" and "practical accuracy". If a majority of your shooting is going to be done with 55grain standard (not match) ammo with an Aimpoint or an ACOG are you really going to be able to see that barrel "A" is capable of shooting .5" better groups than barrel "B"?

If you're shooting 6" steel plates at 400 yards with a 10x optic and match ammo, the difference in accuracy may mean a lot more to you.

Often times as shooters we don't keep our accuracy expectations in the context of our real shooting needs.


http://www.03designgroup.com/photo/which-carbine-is-more-accurate/icon-which-carbine-is-more-accurate.jpg
03designgroup | Which Carbine Is More Accurate http://demigodllc.com/icon/extwh3.png (http://www.03designgroup.com/technotes/which-carbine-is-more-accurate)





Stainless barrel is stainless steel and is a different material than a chrome moly barrel. Stainless steel 410 is a harder stainless steel than stainless 416. 416 is what most manufacturers make their stainless barrels out of.

Cold hammer forging is a process of making a barrel: http://www.rifleshootermag.com/gunsmithing/RSgunsmith1/



Generally a stainless barrel will be more accurate than a Chrome-Moly-Vanadium (CMV) barrel. Not by a huge margin. One example of many, take a look at the info Molon posted in the link below. Compare the group sizes of the Noveske 16" stainless barrel (0.92" average) to the Noveske 16" N4 barrel (1.24" average): http://www.ar15.com/forums/topic.html?b=3&f=118&t=467919 The difference is just slightly more than 1/3" (one third of an inch)

Generally a stainless barrel will have a slightly shorter service life. Don't take this comment to the extreme.


Generally a stainless barrel will a heavier countour and be slightly heavier than a CMV barrel.

Weight comparisions:

http://www.03designgroup.com/photo/ar15-upper-receiver-weight-comparisons/icon-ar15-upper-receiver-weight.jpg
03designgroup | AR15 Upper Receiver Weight Comparisons http://demigodllc.com/icon/extwh3.png (http://www.03designgroup.com/technotes/ar15-upper-receiver-weight-comparisons)



For most of us, practical accuracy is much more important than group size. I don't have a problem hitting smaller than average targets out to 425 yards with a 3.5x ACOG or Leupold 1.5-5x with my standard chrome lined, cold hammer forged (chrome lined), or stainless barrels using XM193, Winchester Q3131A, Federal American Eagle 55 grain, Black Hills 55 grain, and other 55 grain ammo.



For a hard use, high round count, training gun I would select a chrome lined barrel over a stainless barrel.





I wrote this in another thread in reference piston guns:


As a frame of reference I have been hosting 2 to 5 tactical training classes a year, every year since 2001. A side from the classes I host I also take other training classes. I've been a full time Police Officer for 14 years, I've been a SWAT cop for 11 years, and I'm a Firearms Instructor for my agency, our Police Academy, SWAT Team, and SWAT Academy. Prior to that I was in the Marine Corps (Infantry / Security Forces).

In the early 60's when the M16 first came on line there were several important people that wanted to see the M16 fail. So troops were told that they didn't have to clean their guns, they used the wrong powder in the ammo (ie. they were suppose to use stick powder and they used ball powder), etc. By doing this the M16 got a reputation as being an unreliable platform.

In my opinion the reason that the direct impingement gas system (DI) has gotten such a bad reputation in recent years is because people go out an buy low end AR's or they try to build a AR from parts from various manufacturers. They end up with a gun that is unreliable and this feeds into the myth that the DI gas system is unreliable.

When I was in the USMC the main malfunctions were caused from shooting blanks and magazine related. I had seen a hand full of other problems, but they were far and few between.

In the training classes that I host and take on my own and from the AR15's that I see in training and qualification courses at work. Colt, LMT, BCM, Noveske, etc. run well. While CMMG, DPMS, Olympic Arms, Bushmaster, Stag Arms, RRA and others have a high number of reliablity problems.


Piston guns. I have seen a lot of piston guns that have had problems. I have never seen a POF make it through an entire class without problems. About half the Sigs that I have seen have had problems. About 1/3 of the LWRC guns I have seen have had problems.

From my experience piston guns

-have a sharper recoil impulse
-they are heavier
-piston system guns are more expensive
-the different piston systems are new and haven't had the time to be as thouroughly tested as the DI gas system
-many of the piston system operate on a slightly different system

Piston systems on the AR15 is a fairly new concept (most within the last decade). The DI gas system in use on the AR15 has been in service for close to 60 years, this has given engineers time to work the bugs out of the DI system. Not the same can be said for the piston systems used on the AR platform.

In my opinion the piston system is not needed on the AR15 and it exists because guys buy lower end AR15's, many of these lower end AR15's are not reliable, and when a shoorter buys or builds an unreliable AR15 it feeds into the myth that the DI gas system is unreliable. DI gas system AR15's are not created equal. There are different levels of quality.

A well known trainer has a DI gas system BCM upper that had 26,000 rounds through it before it was ever cleaned. Currently the gun has just shy of 29,000 rounds on it. Read this article for more info:

http://www.03designgroup.com/photo/bcm-complete-ar15-upper-and-lower-receivers/icon-bcm-upper-lower.jpg
03designgroup | BCM Complete AR15 Upper and Lower Receivers http://demigodllc.com/icon/extwh3.png (http://www.03designgroup.com/reviews/bcm-complete-ar15-upper-and-lower-receivers)



In short I see no need to buy a piston upper. Buy a QUALITY AR15 with quality ammo, quality magazine, lube it, and it will run without any issues.




Hope this helps

[JonnyVain]

I voted DI. I don't have any experience with piston, but I know they're new to the game still. The AR was designed for DI. Your changing it in a way it wasn't supposed to be used by adding a piston. Unless you're in extreme conditions like desert or jungle, I don't see the reason for going piston.

And if you want a piston gun, try a .223 AK. I know it's not the same thing...

[Skyyr]

And if you want a piston gun, try a .223 AK. I know it's not the same thing...

You bring up a good point though. Trying to slap a piston on an AR is like trying to build a DI AK or chambering an AK in .223. Can it work? Sure, but it wasn't designed around it originally and therefore can never be fully optimized like the original design can be.

[SWATcop556]

Jeff nailed it. I have yet to find something a piston gun can do that I can't accomplish with my DI guns. IMO cleaning should not be a determining factor in buying an AR as it is not a difficult, time-consuming weapon system.

The bugs in the piston systems outweigh the benefits right now (for me at least).

[Failure2Stop]

Two things:

1- Great post by USMC03.
2- The poll questions have some problems.
-There is no need for a carbon scraper for a DI AR unless the user wants one.
-Piston ARs have more felt recoil than similarly setup DI ARs.

[CoryCop25]

DI is a solid reliable platform. There are too many bugs in piston guns at this point. If you want to change gas settings, get a Noveske Switch Block. Just my $.02.

[No Bananas]

Two things:

1- Great post by USMC03.
2- The poll questions have some problems.
-There is no need for a carbon scraper for a DI AR unless the user wants one.
-Piston ARs have more felt recoil than similarly setup DI ARs.

For cleaning my DI, I will need a carbon scraper.

In comparing the two, the AA piston has noticeably softer recoil IMO. Not so w/ some other piston systems. LWRC, in my experience, has a sharper whip in recoil than DI. Go figure. ???


I can see that this poll is going to be a close one. ;-)

[Skyyr]

In comparing the two, the AA piston has noticeably softer recoil IMO. Not so w/ some other piston systems. LWRC, in my experience, has a sharper whip in recoil than DI. Go figure. ???


Then you aren't comparing the same guns. With two identical guns, one using a piston and the other DI, the piston will ALWAYS have more felt recoil. It's physically (as in the laws of physics) impossible for it not to due to the way the piston strikes the carrier. Now sure, you can put in a heavier buffer, run different ammo, etc. to make the piston recoil less, but the same changes would also make the DI gun recoil less.

They're also more prone to short-stroking.

[No Bananas]

The 10.5" upper w/ AA Piston Kit kicks softer than it did before when I bought it as a DI LMT upper. Maybe it's the additional weight of the AA gas block, I dunno. But it definately kicks less. Other folks who have an AA kit have the same experience. Have you ever shot an AA kit? I've never had a short stroke with the AA Kit, and I've never had a short stroke with the DI rifle I have either.

PS: No malfunctions from the 10.5" LMT DI before I converted it.

[Skyyr]

The 10.5" upper w/ AA Piston Kit kicks softer than it did before when I bought it as a DI LMT upper. Maybe it's the additional weight of the AA gas block, I dunno. But it definately kicks less. Other folks who have an AA kit have the same experience. Have you ever shot an AA kit? I've never had a short stroke with the AA Kit, and I've never had a short stroke with the DI rifle I have either.

PS: No malfunctions from the 10.5" LMT DI before I converted it.

Pistons short-stroke more because the force from the gas must overcome the weight of not only the bolt-carrier, but also the piston rod. It's simple physics: more force is required because a quantifiable amount is lost to overcoming the inertia of the piston rod. With a DI gun, the only mass that needs to be moved is the bolt carrier. This means a round that is just barely powerful enough to run in a DI system has a very high chance of short-stroking in a piston gun. It also results in higher failure to lock back after the last round is fired.

The act of piston rod hitting the carrier will jolt the gun, literally. Maybe you don't notice it, but it's happening nonetheless. It's the same reason that carrier-tilt happens. Instead of a smoother, more gradual gas expansion inside the gas key on a DI gun, the piston simply slams back on the carrier and the energy is directly transferred as a physical force into the upper receiver and into the rifle. The DI guns don't have this because their isn't a direct physical transfer of energy (since gas is essentially a fluid and will flow to the path of least resistance) and the only felt recoil is a result of the carrier connecting with the buffer.

It's like a rope: you can pull on it gradually, or you can yank on it at full force. The piston guns will always have a "yanking" effect to them. DI guns won't (speaking relatively about the same gun firing the same round).

[No Bananas]

You hate pistons, I get it. I hear what your saying about how it functions. Go fire an AA Kit. You'll see that the recoil is softer. In comporable guns with the same loads. I'm not saying that it is better than DI. Geez.

[Skyyr]

You hate pistons, I get it. I hear what your saying about how it functions. Go fire an AA Kit. You'll see that the recoil is softer. In comporable guns with the same loads. I'm not saying that it is better than DI. Geez.

I don't hate pistons; they just simply aren't superior to a DI weapon. They present a different set of problems that need to be overcome. That being said, you seem to be ignoring that physics will always be true. It is physically impossible for a piston to run smoother (read: without the jolt) than a DI system on the exact same gun. Maybe you don't notice it, but that's just it: you don't notice it. That doesn't refute the truth.

Putting a piston on an AR makes as much sense as making a direct impingement AK. Can it be done? Sure, but there's no point to doing so.

[No Bananas]

Jimini Christmas! Yes, I did acknowledge what you explained. I said I didn't know why the recoil seemed softer, that it could be the added weight of the heavy gas block:

Maybe it's the additional weight of the AA gas block, I dunno. But it definately kicks less.

Go to AA's website and see all the testimonials of folks who say it kicks less. go to some piston forums and you will see the same. Like I stated before, I understand what you are saying about physics and operation. But, it kicks less. Maybe it has absolutely nothing to do with their piston, maybe it's the heavy gas block, the weight of their one piece carrier or other physics that you don't know about. But those of us who have shot them and own them agree they kick less. In my experience and opinion an AA Kit kicks less than a DI. You have well established that you disagree. Now, hopefully we can let this go. Geez.