Disassembly/Reassembly Of the Sabre XR Rifle

Let me begin by mentioning an article titled "Barrel-Making Goes High-Tech’ that appeared in the May 07 issue. That article was an overview of Sabre Defense Industries and the company’s barrel-manufacturing technology.

The barrels used in the article to illustrate this technology were being made for the venerable Browning 50-caliber heavy machine gun’otherwise known to servicemen as "Ma Deuce." As pointed out in that article, Sabre’s original purpose for coming to these shores was to manufacture premium variants of the AR-15 and M16 for the civilian, military, and law-enforcement markets, but the Pentagon’s need for large quantities of high-quality 50cal barrels pushed that project onto the back burner.

Now, however, with its 50-cal barrel production catching up with military demand, Sabre is now refocusing on the company’s original purpose, and is producing one humdinger of an AR-15, known as the XR-Series. As you probably know, multi-gun shooting competitions are held around the country under the auspices of the United States Practical Shooting Association (USPSA). According to my sources at Sabre, these matches are playing a significant role in driving the AR-15 market.

I was pleased to learn that the Sabre employees who actually work on and produce the XR series also fire them in these competitions. Can you think of a better way for a manufacturer to get quicker feedback on product performance? I can’t. The "hot new round" I mentioned in the subhead above is the Grendel 6.5 mm. I know, we all remember the Grendel semi-automatic pistol’an overcomplicated misery to work on’ and no gunsmith I know was sorry to see it pass from the scene.

Happily, the ill-conceived and ill-fated Grendel pistol has nothing whatsoever to do with the new Grendel 6.5mm round. Invented by Bill Alexander of Alexander Arms, the Grendel 6.5 mm was designed specifically for the AR- 15. Built on the phenomenally accurate 6mm PPC case and packing a 123grain Lapua Scenar bullet, the Grendel 6.5 mm has a ballistic coefficient in excess of 500 and produces a muzzle velocity of 2,600 fps.

Its longrange performance totally dusts off the more commonly used 5.56 mm (.223), and it does so with half the recoil of the 7.62 mm Nato. The ammunition is curre m Alexander Arms Other sources includ nce Ammunition, and I’m told Lapua will soon join the list. So now that you know a little about the cartridge, the competition it’s used for, and the gun manufacturer, how about some technical dope specifically on this XR rifle?

The upper and lower receivers are CNC-machined from forgings of 7075-T6 aircraft aluminum. Barrel blanks start out as heattreated rounds of MIL-S-11595, a highvanadium steel alloy. Hole size, roundness and straightness are held to 0.0005 of an inch. Bore dimensions stay well beneath Mil Spec of plus or minus 0.0004even after button ri- Complete field stripping would include the boltcarrier assembly, handguards, buffer and action spring, as detailed in the text.

F Not shown is the Mag Na Tip bit adaptor for the torque wrench. All are available from Brownells. fling and chrome plating. The plating itself is restricted to a thickness of 0.0013 to 0.0020 inch. At the appropriate time during the process, the barrels are stress relieved. The one I worked for this article was the XRAR15A3, which has a 16inch 1:7.5 twist barrel, an A2 flash hider, and an extended gas tube to reduce felt recoil. Its flat-top upper provides for the mounting of a wide variety of optics.

These features, along with its flip-up front and rear sights, make it an excellent choice for competition’among other things. Let’s start taking down this honey. Field Stripping This is one tightly put-together rifle, so resist all temptation to get brutal with it. After pulling the magazine and racking back the charging handle to make sure the chamber is empty, release the handle and move the selector lever to "safe." You accomplished two things by racking the right, and pull on it until it stops.

Pivot the upper receiver away from the lower receiver. Push the front pivot pin to the right, pull it until it brings you to a halt, and separate the upper from the lower. Next, grasp the charging handle and pull it rearward, bolt-carrier assembly (body) attached. Lift off the assembly and remove the charging handle from the upper. With a small punch, push the firing-pin retaining pin out, invert the carrier, and dump out the firing pin.

Give the bolt-cam pin a quarter turn to clear the boltcarrier key, lift the pin free of the carrier, and remove the bolt to the front. Reach in with a small dowel or punch and depress the buffer-retainer pin. Hang onto the buffer; it’s keeping a mighty strong action spring inside the receiver extension. Ease both components out. At this point you can give the piece a really good cleaning, but I feel there are a few specifics concerning the task that are well worth mentioning.

Cleaning Tips Working from breech to muzzle through the upper receiver, swab the bore with CLP (the manufacturer’s recommendation). If using a sectional rod, back off the last segment (the first to enter the barrel), and make it two turns from tight. Whether you choose a sectional, one-piece, or flexible rod, when you attach a brush or jag to it, let it be two turns from tight. Why? Becharging handle: You checked the chamber, and you cocked the bolt’which you have to do anyway to move the selector lever.

C Now place the butt of the rifle on your benchtop, press down on the upper handguard snap ring, and lift off the guard. Push the rear takedown pin to the cause the brush or patch will clean better if it’s allowed to rotate as you pull it through the bore. Of the three cleaning accessories, I prefer the Otis Technologies kit for cleaning chromelined bores. Sabre Defense must agree. They packed a kit for the caliber with the rifle they sent me.

The kit, typical with Otis, comprises a generous length of plastic-coated, aircraft control cable with a caliber-specific brass receptacle at one end for attachments. Those attachments and a brass Thandle fixture thread onto the cable. With the muzzle pointing down, I carefully lowered the cable through the barrel, avoiding contact with the bore. Sissy stuff? Not if you’re as concerned as I am about scratching a chromed bore.

When two or three inches of the cable extended from the muzzle, I loosely attached a brush to the cable’s breech receptacle, secured the T-handle to the muzzle end at the upper, and pulled it through. With a badly fouled bore, this would have to be repeated at least twice at an absolute minimum. I attached a brush matching the chamber dimensions to a pistol-cleaning rod, doused it with CLP, and inserted it from the rear of the receiver. Rotation’no back-andforth action, please, will do the job.

Then it’s back to the Otis rig, this time fitted with a patch loop and a wet patch. Several of these are pulled through, followed by dry patches, until the last couple come out clean. One more patch or cotton swab follows carrying a few drops of quality lube. The lube can also be used to deposit a light coating on your cleaned chamber, the bolt-locking lugs, and the insides of the upper. We’re not through yet. Clean off all bolt surfaces, and lube the firing pin and its recess in the bolt carrier.

Use additional lubrication on the outside of the bolt-cam pin, firing-pin retaining pin, bolt-assembly cam-pin hole, bolt rings, and the outside of the bolt assembly. Go after any powder residue with a CLP-soaked toothbrush or acid brush. Lube any moving parts you have scrubbed off. Clean all surfaces of the bolt carrier. Finally, use a pipe cleaner to reach into the carrier

Sabre XR-Series Semi-Automatic Rifle (Specifications subject to change without notice)

5 mm (A) is midway in size between the standard .223 (B) and the 7.62 mm Nato (C). key and put one drop of oil inside the key and to lube the exterior of the carrier. The rifle is now clean enough to function without any problems related to dirt. Detailed Disassembly You may want to make separate copies of the schematics included here and refer to them individually as you work with the respective assemblies.

You’ll notice there are no parts numbers on the drawings, so the usual numbers will be missing from this text. There’s no need for them because labels on the drawings identify each component. I like this format and it certainly saves time, since it eliminates the constant cross-referencing between a number on a drawing and the name in a list of parts. To disassemble the barrel assembly, compress the delta ring to the rear, pivot the lower handguard halfway to maintain pressure on the ring, and take off the guard.

Now remove the upper handguard. A starter punch gets the gas-tube roll pin moving from left to right. Switch to a roll-pin punch to drift the pin out fully. Rotate the gas tube a little, move it to the rear of the barrel, then pull it free. Press down on the barrel nut and withdraw the barrel to the front of the assembly. It is a friction fit. When a match barrel is involved, it is secured with Lok Tite, but don’t panic’S abre doesn’t use the red stuff on this union.

Gently heating the receiver or the barrel will break the bond. To remove the spring clip at the rear of the barrel nut, a small pin punch or a set of snap-ring pliers can be used to dislodge the pin from its groove. On some XR rifles, the frontsight base is secured to the barrel with two tapered pins. These are started left to right with a pin punch, and then drifted totally out with a cup-pin or straight-drive punch. On the XRAR15A3, the base is attached with four socket-head screws running through two brackets.

Routinely, there’s no need to remove the base. If it’s damaged, however, the flash hider has to be taken off the barrel first. This is done with a thin 3/4-inch wrench (knuckle-buster variety), turning the flash hider counter-clockwise as you look at the muzzle. The sight can now be rotated and carefully driven off the barrel. The other reason you might have for getting the sight out of the way is if you ever need to get at the handguard cap. The sight retains it.

Pictured here along with other needed tooling is an AR-15 receiver action block (Brownells #702-003- 015) that protects the upper when it’s locked in a vise. Following the instructions that come with the action block will make your life easier as you continue on with the disassembly of the upper, bolt, and bolt carrier. In field stripping, you took out the bolt cam and removed the bolt.

Let it rest while you undo the bolt-carrier key screws and take off the key. (Note: These are staked in on both sides at the factory and must be similarly restaked in reassembly.) The bolt gas rings are next. There are three of them, and each has a gap. Ascribe will help in getting them off the back end of the bolt. Just remember when you reinstall them that those gaps must never be aligned. The middle ring’s gap is positioned at 12 o’clock, with the rings fore and aft of it at 3 and 9 o’clock.

It’s your choice which goes at 3 and which at 9, but if you ignore the noon, three, and nine rule, the rifle will short cycle. It’s a gas system thing. And one of the primary causes of malfunctions with any AR- 15 is "someone" disassembling the rifle and then carefully aligning these gaps during reassembly. The extractor and ejector assemblies are retained by two pins.

Start them downward, but before drifting them out completely, you must be prepared to capture the ejector and its spring along with the extractor spring and its insert. With the latter, put some pressure on the extractor and ease it plus its related small parts away from the bolt as the pin is removed. Unless the ejection port cover, spring, pin, and pin-retaining clip have been run over by an 18-wheeler, leave them on the upper assembly. The reason is the spring.

It has to be wound before being reinstalled in the cover, then held in position and speared by the cover pin. The spring will naturally attempt to unwind all by itself while you try to keep it from doing so. The forward assist itself presents

no similar problem. Press in on the plunger, start out the pawl-spring roll pin, and keep pressing on the plunger while drifting the pin completely out. This gives you free access to the balance of parts in the assembly. Unless there’s some serious damage, I advise against a takedown of the rear sight. As you can see, there are numerous tiny components, and every one of them is easily lost. If a sight gets broken, replace the whole thing.

If it gets dirty, run the elevation knob up as far as it can go, grab a can of Gun Scrubber or brake cleaner, an acid brush, and apply both to the crud. A light lubrication after this cleaning will enhance further sight function. Regarding the lower, install an AR- 15 magazine filler (Brownells) in the receiver and clamp it between padded vise jaws bearing on the magazine well. Release the tension on the hammer and ease it forward into the fired position.

About the hammer: It contains a crimped-in J-spring that should be left as is. Also, the tail of the hammer spring exerts pressure on the groove in the trigger pin, which, by the way, is identical to the hammer pin. Give the hammer pin a nudge with a drive punch. Remember those springs mentioned and hang onto the hammer while you drift the pin the rest of the way out. Depending on the nature of the screw head, along-shank hex wrench or hollow-ground blade driver undoes the grip screw.

The safety-detent spring is housed in the grip, so be careful when separating the hand hold from the lower. The safety lever has to be rotated to a place halfway between "safe" and "fire." Press inward on the opposite side of the lever to get it moving, and then pull it from the receiver. The safety detent is pushed downward and out of the lower with a length of drill rod or a parallel-sided drift. Note on the schematic that a couple of springs are placing tension on the disconnector/trigger assembly.

When you push the trigger pin through the lower, leave the drift in place. Hold onto the disconnector as you remove the drift, at which point you’ll feel the spring tension fighting you. Control it and maintain control as you ease the assembly down and out. The trigger-spring coils have been squeezed together before being placed between the upper "ears" of the trigger. Don’t yank out the spring.

Slip a small-blade screwdriver or piece of shim stock between one ear and a coil of the spring, and compress the coils slightly before removal. Avoiding damage to the finish on the lower when removing the bolt catch requires some preventive measures, but before getting into those details the stock has to come off. Back out the buttplate screws. The butt-cap spacer will either stay stuck in the stock or fall off. It rarely remains attached to the receiver extension.

Once the stock is gone, the takedown-pin detent and spring will be exposed. Take them out and remove the pin. Now back to the bolt catch. Its roll pin is located in a manner such that getting it out forces you to lay your punches, both starter and roll, parallel to and up against the side of the receiver. The possibility of marring the finish is obvious, so lay down a strip of duct tape or a couple of strips of masking tape before you put the punches to work toward the rifle’s muzzle end.

Press in on the magazine catch to the maximum and begin to unwind it. The shaft of the catch, threaded on one end, runs through the catch spring and ends up retaining the catch button. Once parted from the catch, both spring and button will drop from the lower. Next insert a short length of straightened paper clip into the hole in the front pivot pin. Use it to rotate the pin, depress its detent and spring, and pull out the pin. And, yes, both the detent and spring will take off big time if you let them.

What you’re left with at this point is a detail-stripped upper, barrel assembly, and a lower with the barrel extension still attached. The extension is torqued on and can be cleaned out where it is. If you have a torque wrench, though, and the extension is damaged enough to require replacement, take a quick reading on the inch-pounds it’s been tightened to and match that in reinstallation. Otherwise, I suggest you leave it alone. Speaking of torque wrenches, you’ll find a specialized one pictured.

It’s built to tighten the carrier-key screws to their specified 35 inchpounds. When it reaches that point, the wrench turns freely and tightens no more. It’s not the cheapest of hand tools, but when equipped with its Mag Na Bit adapter (sold separately), it’s perfect for properly resetting those key screws before they’re re-staked. Reassembly Tips Normally I provide some tips, but this time I’m going to suggest you get a book from Brownells. It’s written by Walt Kuleck, a Ph.

D. with Fulton Armory, and Clint Mc Kee. In 150 pages, they take you step by step in clear pictures and succinct text through the assembly of an AR-15. The tools you’ll need are also described. After reading the book myself, I feel confident in saying any gunsmith who was handed a box of parts adding up to a complete AR-15 could put them together and end up with a safe, perfectly functioning rifle. I