Recycling AR-15 Barrels

Along time ago I remember shooters talking about gun barrels only wearing out at the back with claims that a shotout barrel could be pulled off of a bolt gun and given anew lease on life. A gunsmith would cut another thread on the rear of the barrel and remove the same amount from the back, then run the chamber reamer back into the barrel and reestablish correct headspace, making it as good as new. Some of the guns allegedly were .22s and others were centerfires.

I figured that anyone shooting out a deer rifle either had to be way outside the law or the worst shot on the planet. I made it a point to ask everyone repeating this claim if they actually knew anyone ever doing this and the answer was always a reluctant, "no." I began to wonder if this recycling was real or just more "encyclopedic error," something that has been repeated so often that nobody questions it but that may not be born of any real, provable fact.

My interest in firearms at the time was limited to hunting and legally filling my game bag. Such pursuits are not as ammo intensive as competition shooting so I had no guns with shot-out barrels on which to test the "recycling" theory and the idea just lay dormant in the back of my mind for a few decades. In the early 1970s I was shooting Practical Police Combat (PPC) matches.

Cops were still carrying revolvers and it was quite common to hear the same rumor about cutting anew thread and reusing shotout revolver barrels but, again, I was unable to actually find anyone who ever claimed to have done so. As an aside, if you shoot lead bullets and light powder charges through a revolver, the barrel can last 200,000 rounds so not many folks ever really shot one out. This is much higher longevity than most rifle shooters can even imagine.

Fast forward to the late 1980s when I was competing with the Army Reserve Marksmanship Program and wearing out at least one M14 barrel a year. Remembering the "recycling" theory I took a good hard look at the M14 platform and figured that any attempt to recycle barrels for that gun would have to move the gas port rearward more than Mother Nature ever intended, perhaps making the whole notion untenable. I put the recycling theory back into mental storage for a spell.

The M14 wasn’t the only service weapon the Teams were using. The Combat Team tried the M14 for a season or two but found it to be cumbersome and too heavy in recoil to be competitive against the foreign teams using various assault type rifles firing 5.56mm. We initially switched to the M16A2 and iron sights, but as successful foreign military teams began using issue optics, we tried mounting the issue Trijicon ACOG to the A2's carry handle.

The scopes tended to jar loose and were way too high to establish any kind of cheek weld, resulting in troubling parallax. Use of the A2 uppers was short lived and the flat top became the best solution. Courses of fire were evolving to be more realistic and to better prepare soldiers for modern warfare. Time limits were getting much shorter and there were many quick engagements where targets appeared at random across a frontage and then quickly disappeared.

The US competitors were at a distinct disadvantage with the full length 20" flat top against some of the foreign bullpup designs used by the British, Australian and other teams. Some of us dropped the 20" uppers for shorter 14.5" M4 flat tops and found the carbines to point faster. Since we were using ACOGs there was no accuracy penalty with the carbine’s shorter sight radius.

First Attempt During all these gun changes I was using a 1:12 twist Krieger 20" chrome-moly barrel with an HBAR contour for training that shot issue 55 grain FMJ ammunition really well. The combination of slower twist, tall 0.218" land, cut rifling, quality Krieger barrel steel, an original chamber with a short free bore, minimal cleaning rod damage, and slightly cooler burning ball powder used with the 55 grain issue load allowed me to go into five figures on my round count before accuracy started to deteriorate.

In all fairness, combat rifle targets tend to have slightly more generous scoring rings than National Match bullseye targets. This is because most combat courses of fire are of much shorter time limits and rack grade military firearms shooting issue ball ammo are not as accurate as match guns. I believe the slightly larger scoring rings of the combat targets allowed me to get a few thousand extra rounds from the parent Krieger barrel.

This was right around the time some were switching to carbines, so I decided it was time to try the barrel recycling theory. I figured that at over 10,000 rounds the original barrel had paid for itself so even if the new barrel failed to work out I was still ahead of the game. The only risk was the machining time and work. I set very few rules for the project. The one rule that I refused to vio-

This is a "parent" barrel eligible to be cut down and recycled. Next is a 16" recycled carbine barrel with mid-length gas tube shown with cut off "stump" to the left. The fluted 20" barrel is not a "parent" candidate because the flutes extend too far rearward. The 20" A2 barrel with skinny GI contour is too thin to rechamber.

Below that, 20" barrels can be recycled to a 14.5" M4 length for use by customers possessing an NFA-legal lower. late was to invest no more machining work in the project than it would take to make a carbine barrel from anew fresh blank. I cut 5.5" off the back of the barrel, rethreaded it for the extension, and chambered it. The outside 1" fat contour of the parent barrel was turned down to issue M4 skinny specs under the handguards. A fresh crown job, a dip in the Parkerizing tank and I was done.

The parent barrel already had the threads on the front for a flash suppressor. I followed that by properly mounting the barrel in a flat top upper receiver. For the specifics on how to do that see my article, "The Relationship Of Barrel Extension Diameter To Accuracy In The AR-15" in the March and April 2013 issues.

Next, I fired a normal ten round break in, cleaning after each shot, as detailed in my article, "Gas Gun Barrel Break- In" in the October 2014 issue and "Barrel Break-in for AR-15 Competition Rifles" video on the American Gunsmith blog. Really, all I was breaking in was the new throat of the chamber. After that the gun was ready for a trip to the test shed. Velocity loss was about 150 fps.

A handy estimate of velocity loss is 25 fps per inch of barrel, which I have found to be fairly close in shorter 14 to 20-inch lengths but not so much in the longer Match Rifle lengths. The bigger concern was accuracy. The new carbine barrel shot groups every bit as tight as the parent barrel had when it was new. The only monetary expense was to purchase the shorter (9.75") gas tube.

I was very pleased with the project and still haven’t worn that carbine barrel despite getting a second 10,000 accurate rounds through it when the Army Reserve Team needed anew armorer and I gave up competitive shooting to help my teammates. Getting an expected, accurate 20,000 round count out of a blank that goes for about $300 today was time and money well spent.

Depending on your shooting discipline, its accuracy requirements, and the type of ammo shot you may not get the kinds of round counts I enjoyed on my maiden barrel recycling venture. Characteristics of the parent barrel such as quality of barrel steel, button rifling vs. cut, land height, and land-to-groove ratios will all enter into the longevity equation. Cleaning practices will also be key to how long your barrel will last. Especially important will be your chamber selection.

If you select a chamber with significant freebore, expect accuracy to deteriorate quickly on both parent and recycled barrels. My "AR-15 Chamber Selection" series in the July through September 2014 issues goes into this further. There are many factors influencing barrel longevity, as detailed in my "Barrel Wear Out" articles in the June and July 2014 issues. Too Much Gas! What I experienced with my very first break-in round was predictable and expected: Greater felt recoil.

Felt recoil in any semi auto is the product of two reactions. The first occurs due to the acceleration of the bullet down the barrel, which is present in all firearms. The second recoil pulse is unique to self loaders and is caused by the bolt carrier sent to the rear by gas impinging on the bolt in the AR-15. That movement is usually stopped when the back of the buffer hits against the rear of the buffer tube and can’t go further.

The compressed buffer spring pushes the carrier forward and eventually into battery, causing another jarring sensation. This cycling occurs quickly and during the same period as normal recoil from the accelerating bullet that all we shooters feel is "kick" moving us off target and delaying following up shots. Cutting 5.5" from the parent barrel increased felt recoil because I moved the new chamber closer to the gas port still in the same place and size.

In a regular 20" barrel the expanding gas from the burning gun powder has roughly 13 inches before reaching the gas port but reaches the port of an M4 much earlier (about 7" in front of the rear of the chamber) when it has greater pressure. The earlier impingement of gas on the AR bolt makes the gun want to unlock

From top, AR-10 barrels can be recycled if the gas port is located two or four inches forward of normal placement and remains full diameter far enough forward to accommodate the new chamber. Next, a 26" AR- 15 barrel with gas port two inches forward eligible to become a parent barrel. Below that is the same barrel after recycling, now 24" and used with a standard length gas tube. A 20" Service Rifle barrel made by recycling a shot-out 26" parent barrel.

Finally, a 26" Match Rifle barrel recycled down to a 16" carbine length, which works provided the excess gas is controlled. Above Center: Adjustable gas blocks, adjustable front sight housings and adjustable gas tubes can be used to compensate for excess gas when recycling. Some of these devices are called "cyclic rate reducers" and perform double duty reducing ammo consumption in full autos. and cycle sooner than full length barrels.

Called "dwell time" (how long the bolt remains locked up), issues regarding the short barreled ARs wanting to extract too soon were problems in getting reliable carbine function. Designers working on the carbine found that not only was the timing of the gas an issue but so was its volume, which is what barrel recyclers are concerned with.

The factory carbines now have a small gas port size of 0.063" where full length 20" barrel ports range from 0.093" up to nearly 0.1" depending on who is drilling and their preferences. When full length barrels are chopped and recycled to carbine lengths, more high pressure gas meters through fat gas ports than is needed and this causes the carrier to slam hard to the rear increasing felt recoil. Not to worry, there are solutions!

Dealing With Excess Gas I do not claim to be the first gunsmith to recycle an AR barrel. When I started my first project I looked at what others had done with regard to gas. Some used the existing gas port as a sort of pilot, drilling a considerably fatter hole centered on it, female thread tapping the hole, then screwing an appropriate-sized plug into place, likely coated with Loctite and dressed to the top contour of the barrel.

This plug doesn’t have to be pretty, just functional, because it is going to be covered by either a gas block or front sight after drilling a carbine-appropriate 0.063" port. The combination of being screwed in place, Loctite, and the gas block or front sight holding the plug captive ensures that it remains secure. Advantages of this approach are invisibility and you end up metering the true amount of gas that has been proven optimal for carbine function.

From a dollar standpoint it is cheap but not from a labor perspective. The approach I commonly use is an adjustable gas block. These are particularly good if one will be mounting optics and many have a section of Picatinny rail on the top, allowing detachable front sights to be mounted. Brownells also lists front sight housings that adjust for gas flow and adjustable gas tubes.

Derrick Martin’s The Complete Guide to AR-15 Accuracy details inserting a set screw through the front of the gas tube to make adjustable tubes. Another option is to accept more gas and slow down the buffer so it doesn’t impact the buffer tube as strongly. A simple way to do this is substituting a heavy buffer spring. While these do effectively slow the buffer, they also speed it up forward travel, adding to that component of secondary recoil.

There are also buffer replacements, such as those resembling miniature automobile shock absorbers. The ones I have tried work well. It’s important to test fire any time changes to the original firearm design are made. Other Recycling Opportunities While my first attempt at recycling AR barrels resulted in an M4 barrel, the National Firearms Act may raise legal concerns for barrels that short for your customers.

I was using mine with an Army Reserve Team-issued M16 lower so I was fine but it may be illegal for most of us to assemble such short barrels on civilian-owned AR-15s, so most of our short recycled barrels will be 16". These will use mid-length gas tubes measuring 11.75". Longer AR barrels can be recycled in some cases. Some 26" barrels can be shortened two inches as many of us drill our gas ports that far forward of standard barrels.

This increases dwell time, lengthening the time the bolt stays locked up, which may help with primer retention when shooting

hot loads. Locating the port further forward necessitates a 17-1/8" gas tube (I get mine from White Oak.) When recycling a 26" match rifle barrel to the shorter 24", go back to a standard 15-1/8" gas tube. When locating gas ports on match rifles two inches forward it is common to drill them just a tad fatter because gas pressure is supposed to drop off as the port is moved further from the chamber. Mine are drilled to 0.106".

This is a very subtle departure from the standard 0.093" and shooters will be hard pressed to notice an increase in felt recoil when 26" barrels are recycled to 24". What about velocity loss? While the prediction of 25 fps per inch of barrel holds fairly true in tubes in the carbine to standard length, the velocity gains from longer barrels is less pronounced. My chronograph tests found an average of increase of only 27 fps total, not per inch, from a 26" barrel compared to 24" when testing a variety of ammo.

Obviously, going from a 26" match rifle barrel to a recycled 24" will shorten sight radius. Those concerned about that can attach a "bloop tube." Note it’s well documented such tubes change barrel harmonics and can increase or decrease group size. This can be compensated for by adjusting loads or varying the torque of the barrel nut. Some of the very high-end extension tubes have integral tuners that may be faster and more user friendly, but are fairly expensive.

If you don’t want to recycle a shotout 26" barrel, you can cut 2" from the back and 4" from the front and end up with a 20" Service Rifle barrel. My match rifle barrels are contoured to a short 1.5" section at the very end of the barrel turned down to 0.750" for attachment of the front sight. Behind that the barrel is fatter. This would need to be turned down to the normal 0.750" Service Rifle contour for attachment of the A2 front sight.

I suppose if you wanted to you could also recycle a 26" barrel all the way down to 16" carbine length (cut 2" off the back and 8" from the front) but you would need to be very aggressive in controlling gas flow due to the gas port of the long barrel being way too big for a short carbine barrel. General Rules The parent barrel has to be thick enough to contain the chamber. When cutting down 20" barrels, the back of the shortened AR-15 barrel needs to be a full inch for chambering purposes.

Twenty-inch match-grade Service Rifle barrels often have an HBAR or CMP contour an inch thick under the handguards and stepped down to 0.750". This can be left at full thickness to the end of the handguard or turned skinnier just forward of the chamber at the preference of the customer. Standard issue A2 contour barrels are not candidates for recycling because they go skinny right in front of the original chamber.

Although I have never done so, AR-10 barrels should be candidates for recycling as long as they meet the minimum diameter to hold the chamber. That diameter is fatter than an AR-15 because of the bigger cartridges fired and the AR-10s I’ve built have been nearly 1.2" in diameter around the chamber area. It is very common for AR-10 match rifles to have their gas ports located two to four inches forward, making them candidates for recycling.

AR-10 match rifles often have 24" to 30" barrels, though the Army Marksmanship Unit is having success with 20" lengths for long range Service Rifle events. While AR-10s are chambered in a variety of calibers, Service Rifles must use an issue cartridge. Parent barrels need to be .30 caliber to be recycled to 20" length. Any time you are evaluating a potential parent barrel for competition thoroughly research the match rules to ensure compliance.

For example, the National Rifle Association and Civilian Marksmanship Program have very rigid requirements Service Rifles. Extending gas ports or front sights, increasing overall barrel length or contours forward of the handguard from the as-issued specs is forbidden. However, the gloves are off when competing in Match Rifle events and modifications are common. Selecting Parent Barrels Let’s be very clear about the objective of recycling.

You are starting with a "shot out" longer barrel and end up with a shorter one. That must always be done by taking some off the back of the barrel where throat erosion, roughening, and fire cracking has caused the loss of accuracy. This will necessitate rechambering. In my article on AR chambers I made it clear to polish every AR chamber and detailed how. Glen Zediker’s stellar The Competitive AR15 Builders Guide also covers this.

While some shooting disciplines, such as revolver shooters, may only require shortening the back of the barrel by the amount necessary to cut one additional thread, the minimum rear cut off amount for Stoner platforms is two inches. I have a few criteria when selecting parent barrels to cut down. First, I want an original barrel that shot well when new. I confess to never having tried cutting down a poor shooting barrel as I considered it too risky.

As a military armorer, however, I had a large volume of shot-out parents to select so I could afford to be choosy and hedge my bets. I do a thorough job of bore scoping and cull any parent that is pitted even if it was still shooting fairly well. Pitting up near the crown always discouraged me the most. I look at the gas port erosion and am leery of anything jagged. All gas ports erode and look unsightly but that doesn’t seem to harm performance. I don’t worry about deep gas port erosion.

Remember, the groove is about the same diameter as the bullet. Anything below the groove in depth is not going to touch the bullet anyway. I look at the forward stopping point of fire cracking to be sure that my proposed rear cut off amount is

going to remove all the cracking. Most all bore scopes magnify so it is sometimes difficult to estimate how far forward fire cracking extends in terms of inches. If in doubt stop the scope at the last point of cracking and put a little witness mark on the scope with a Sharpie where it intersects with the rear of the barrel. Then just pull the scope out and lay it along side of the barrel until the witness mark lines up again to see where the fire cracking ends.

Gain twist barrels can be candidates for recycling but you need to consider what bullets the customer intends to fire. The front of the barrel is key as the last twist rate before the bullet exits determines the RPM and ability to stabilize. I prefer rear cut offs that allow me to use readilyavailable gas tube lengths. You need not necessarily follow that example, however, as cutting a section of gas tube to a custom length to match your specific project is simple.

I’ve carried out a fair number of these AR barrel recycling projects and always ended up with good accurate end products that saved my customers a lot of money. No complaints to date. Regarding money, let’s say you invest $100 worth of shop time in the machining.

Assuming you started with a premium brand barrel in the first place, you can easily mark up a recycled barrel and sell it American Gunsmith Mailing List Policy Like many other publishers, we make portions of our customer list available to carefully screened companies that offer products and services we believe you may enjoy.

If you do not wish to receive these offers, and/or information, please let us know by contacting us at: American Gunsmith Opt-Out Program Big Sandy, TX 75755 Please include your current mailing label. for $200. If the customer started with anew premium barrel blank and had you do the same amount of work he would end up with a total investment of $400. So, on a recycle project the customer will think you area hero for saving him $200.

The customer could start with a brand new "low bid" barrel blank and bring the bottom line cost down some but based on my experience with hundreds of such blanks I would put my odds on getting better results with the recycled premium barrel. Low priced blanks are not a bargain as you may have to go through ten of them to find a really good one. The Army Reserve paid for the other nine.

On a team of mostly of High Masters, what could I do with the rejects? "Repetition does not transform a lie into the truth" as Franklin D. Roosevelt once said. Just because a barrel company says their barrels are "premium" or "match grade" along with wild accuracy claims, that doesn’t make it true. Star Trek fans know the 239th Ferengi Rule Of Acquisition: "Never be afraid to mislabel a product." I’ve scientifically machine rest tested hundreds of AR barrels over the decades.

In my experience, the number of barrels that shoot honest ten shot groups with quality match ammo in excess of MOA greatly outnumbers those shooting MOA or below, especially when assembled on uppers using conventional "hurry up" methods. Buyer beware! Speaking of costs, as the Armorer for the Army Reserve Marksmanship Program for over a decade I found very cost effective ways of doing things.

Of the big military shooting teams, the Army Reserve was comparatively the "poor kid on the block." Using innovative techniques like recycling AR barrels helped me stretch a limited budget which ultimately comes from taxpayer wallets. Most of us, at the lower levels at least, try to be good stewards of taxpayer money and since I experienced no accuracy loss with recycled barrels I believe I did justice by my shooters and the taxpayers.

With regard to funding, the skills that shooting team members gained and demonstrated with those recycled barrels were passed on to your sons and daughters serving in the military who were put in harm’s way since 9/11. Members of both reserve component shooting teams (National Guard and Army Reserve) conducted classes and ranges at power projection platforms that Soldiers mobilized through on their way to face combat.

I am sure that the superior training that these Soldiers received in marksmanship helped save numerous lives. Remember, the cost of one cruise missile will fund an entire military rifle team for a year! You now have an interesting new tool to put in your gunsmithing tool box. Not many customers will approach you to recycle an AR barrel because they don’t know to ask.

If recycling is something you’re interested in, educate your customers, perhaps by making a recycled barrel and displaying it with test targets at your shop or gun show table. I would never sell a recycled barrel as new and telling potential customers you do this will have them asking about it. The novelty of the whole process will likely encourage more potential buyers than it will discourage. AG