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Look back in the archives, Mrraley had some good discussions,on,piston rifles. A key is the AR was not designed from the start to be a piston weapon. So any manufacturer adding one needs to do their homework about effect on balance, reliability, durability, ammo compatibility and a host of other factors. And that is just to prove equivalence to direct impingement AR’s.  To prove superiority they would have to do tests of 10’s of 1000’s of rounds, and have a significant difference. An argument can be made whether a piston driven rifle is even still an AR . 

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I have a Sig P716 with a 12.5 inch barrel, piston gun and a very comparable DI gun with the same barrel. The piston gun needs constant cleaning, starts with jams at 70-100 rounds. The gas build doesn't have 400 rounds yet but other than a few missed beats real early on it has been flawless with nothing more than a wipe with a paper towel and a couple drops of lube. Same barrel but the DI gun is over a pound lighter and much better balanced.

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WAY back in the 1980's we still had quite a few early M-16's left over from the Vietnam era.  They had the early sights you have to use a bullet to adjust, and some didn't have forward assists.  Since they were training weapons no big deal, we cleaned them after every range  day (actually the students cleaned them) and they were kept in perfect working order.

Everyone once in a while we would get a servicewide message to expend certain lots of ammunition for one reason or another.  I loved getting those messages because it called for a range day with the M-16's and most of the shooting was done on full-auto.

We'd load stacks and stacks of magazines and start expending the ammo on full auto. Usually thru just one or two weapons taking turns and having a few competitions to see who could put the most rounds on target.  At some point the barrel and hand guard would get so hot we'd have to wear a glove.  I can't ever remember a malfunction with any of those early M-16's, even with us running scores and scores of full magazines thru them on full auto, and those weapons were early versions and typically not dubbed as reliable as the later A2's and M4's.

Looking at it from a civilian standpoint and not having full-auto (well at least most will not) I don't see a flaw in the basic direct impingement system right to start with.  They work, and work well,  and not known for reliability issues right to start with.  It's still a "closed" system and no moving parts to clog or get all fouled up aside from eventually I suppose the gas tube could get restricted if you ran it for many outings without cleaning it, but I've never seen this happen to date and most of us clean our weapons after range days......Cliff

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Good read!

What some folks doing this sort of thing don't realize is that the quality of your parts does make a difference.

Each part for a Military grade weapon is built to a Mil-Spec.  I used to get into the Mil-Specs some when I was on Active Duty and it amazed me at that time how even a tiny little lock washer had nearly a full page listed for it requiring it to meet a long list of specific specifications in order to be on the selection list for Government purchase.

One thing I've noticed about AR's in general, especially AR-15's is that chrome lined barrels and chambers have almost become a thing of the past.  Companies are advertising "nitrided" barrels (or no mention at all if and what they are lined with), which isn't even in the realm of reality close to chrome plating.  Nitride basically forms a better surface as far as hardness and improved wear properties, bit it does NOT inhibit rust and corrosion like chrome plating.

Pretty important stuff if you are interested in "running" your AR pretty hard for multiple outings and no plans of cleaning it. 

When I first started building AR's I looked for and insisted on chrome lined barrels/chambers.  I wanted Mil Spec as well but that proved to be difficult and confusing.  I also built most of mine with the later 5.56 designation and 1-7 twist.  These days to be price competitive companies aren't offering the better barrels and often you can't even tell what if any surface preparation was done to them to prevent rust/corrosion.

Then you have folks argue that chrome plating kills accuracy so they shy away from them.  I woln't get involved in any of those arguments but for sure I build almost all of my AR's with chrome lined barrels/chambers. 

Stainless steel is another popular option, but stainless does not have the same properties nor does it completely guarantee that they will not rust.  I've seen plenty of stainless steel parts over the years develop rust, black spots, and even pit out when left exposed to moisture and other chemicals for long periods of time.  Cripe I just pulled out my stainless steel hunting/skinning knife and saw yesterday to process a nice 9 point buck and my saw (put away without a good cleaning and drying last season) is rusted pretty badly on one side.  The rust came off with steel wool but left permanent black spots/minor pitting on it.

Good new for all of this is that I've built several AR's with lower end barrels and guess what?  They run just fine and to date I've never had the first issue with any of them.  Can't say as I've ran 14,000 rounds thru one yet w/o cleaning, but we have had some pretty long range days shooting many hundreds of rounds and to date none of the lower end builds have given  us the first problem in any area.....Cliff







Edited by Cliff R
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One of my dedicated varmint AR-15's built on a Rock River lower has a PSA upper with a chrome lined barrel.  I never even looked at it closely until yesterday as I was in the gun safe fetching my 22 bolt action rifle.

The barrel is only 16" and stamped "5.56 NATO CHF 1/7".  I've had it for quite a few years now, it's topped with a 4-16 Nikon with an AO.  I can't ever remember missing a ground hog (or anything else) with it.  CHF is some of the early Chrome Hammer Forged stuff they used to offer (they may still offer them but haven't looked on their website for quite some time).

Couple of months ago I was set-up on a fresh cut hay field.  Leaning over a big round bale one morning as the sun came up NOTHING moved for over an hour. Being a little bored I picked out a dead tree about 400 yards or so into another field, there was little if any wind blowing at all so a good opportunity for some long range fun.  About 2/3'rd of the way up the tree was a dark spot, so I fired three rounds at it.  I was just hoping they would be on the tree someplace.  To my surprise when I got down there all three rounds were pretty close together but nearly 10' below the point of aim. 

I haven't been back over there with the rangefinder to get the exact distance but it's going to be in excess of 700 yards as it's 300 from the bale to the fence in the field I was set-up in.  I attached a couple of pics below, my knife is stuck in the lower bullet hole, the second pick is from the upper field where you can see where the dead tree was located.....Cliff



Edited by Cliff R
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