Ruger's SR-762 308 Part 1

We've always found the Ruger SR-556® to be a  standout; excellent fit and finish, demonstrating a high degree of accuracy and the 2 stage piston driven operating system has been rock solid reliable and clean running. Ruger has taken all of the excellent qualities found in the SR-556 and applied them to a product with greater range, and a lot more thump - in the form of the new Ruger SR-762.  



Ruger SR-762

Manufacturer
Sturm, Ruger & Co.

Model#


5601

Type


gas-operated, piston

Caliber


308 Winchester / 7.62 NATO

Mag Capacity


20 rounds

Barrel Length


16.125"

Rifling


1:10"

Weight


8.6 Lbs

Overall Length


34.75" - 38"

Stock


Collapsible

Receivers


Aircraft Aluminum
Receiver Finish Hard Anodized
Barrel & Gas Block Parkerized

Length of Pull


11.50" - 14.75"

Sights


Rapid Deploy - Folding (Samson)

Accessory Mount


Picatinny Rail

Trigger Pull


8 Lbs. 1 Oz. Single Stage

Safety


Rotating

MSRP
$2,195

Actual Weights and Measures
Includes 3x20 round magazines, sight adjusting
tool, 2 x accessory rails, rail guards and soft case


308 Winchester power

With this introduction, Ruger extended its SR autoloading rifle line to a firearm suitable for hunting moose, elk, and black bear. Longer range shots at deer and antelope grazing on the plains power, big black bear dropping power. Why the 308 Winchester? Why not just chamber the SR-556 for one of the higher power cartridges designed for the AR-15 platform? Despite some of the more... ferocious names, AR-15 compatible cartridges are limited in size by the system's short cycling stroke and small bolt face. Subsequently, their ballistics pale in comparison to those of the .308 Winchester.
Cartridge Bullet
Grains MV
FPS ME
Ft-Lbs 300 Yd
FPS 300 Yd
Ft-Lbs 300 Yd
Drop
223 Remington 62 3100 1323 2147 635 -7.1
6.5 Grendel 123 2580 1818 2090 1193 -9.2
6.8 SPC 115 2775 1966 1996 1117 -9.0
300 AAC Blackout 125 2215 1360 1441 576 -16.5
30 Remington AR 125 2800 2176 1887 988 -9.6
450 Bushmaster 260 2180 2743 1140 751 -23.0
458 SOCOM 300 1750 2040 1033 711 -32.5
50 Beowulf 325 1800 2339 945 644 -37.6
308 Winchester 168 2840 3008 2270 1921 -7.5

All cartridges with 200 yard zero

The 308 Winchester hangs onto velocity longer than any of the rounds listed on the table above, which means it also has higher kinetic energy and bullets stay in the good graces of gravity over a longer distance. The 223 Remington is an exception in that is has minutely flatter trajectory, however, the 308 Winchester carries 3 time the energy at 300 yards. Do the same numerical assessments have tactical, law enforcement and personal security implications? I am sure they do, however, I'll leave those assessment for someone more qualified in those areas.

The SR-762 is compact...

In the world of ARs, anything chambered for the 308 Winchester or a 308 Winchester derivative cartridge, generally is a lot more hefty than an AR-15 type. The action and related subsystems have to be scaled to accommodate the larger cartridge, which means it would require what an old Air Force buddy of mine used to refer to as "mo' metal". In the case of the Ruger SR-762, apparently the design resulted in a need for minimal mo' metal.  In terms of overall size, with the stock fully extended, the SR-762 is only 2" longer than the comparably barreled SR-556 and only 8 ounces heavier.



In terms of weight? Rather than running for the plastic molded parts in an effort to reduce weight, Ruger stuck with steel and aluminum where, and in the amounts, required in a quality firearm. Some weight was saved with the lightweight adjustable stock assembly on one end and through the use of a 16.125" cold hammer forged 41V45 alloy steel barrel on the other. Fluted and manganese phosphate Parkerized on the outside, both the barrel's bore and chamber are chrome lined.

Smart to leave some things alone...





http://www.realguns.com/images/frntrearst762samsonsights.jpg

The rear sight is adjustable for windage, 1/2 MOA click and the front is adjustable for elevation with the tool included with the SR-762, however, increment of adjustment varies with distance between front and rear sights. The rear sight has rocker selectable apertures, deployed with the large aperture (0.176") in alignment, a flick of the thumb substitutes a small aperture (0.069"). The front sight has an H&K type brush guard. For those wanting more visibility, there are user installable Tritium and Fiber Optic replacement front posts.

Psst... The operating system.

Ruger's description of the SR-762 as a gas-operated, piston driven, box magazine fed, autoloading rifle... which tells everyone that it is NOT an AR-15 type direct impingement type firearm that pumps hot gases and powder residue out of a small port, down a tube the length of the barrel and into a bolt carrier key that sits atop the bolt carrier. The SR-762 bleeds gas from the barrel, but uses it to drive a piston that actuates a transfer rod that mechanically drives the rifle's bolt carrier. Subsequently, there is only a flat contact pad on the bolt carrier and no bolt carrier key... and a very clean assembly.







[The regulator has 4 positions numbered 0 - 3. Position "0" is no gas flow and the rifle will function as a single shot with no gas flow to cycle the rifle's action. Each successive number allow a freer flow of gas from the barrel to the piston. Terrific for folks who change brands and types of ammunition or who handload. Gas can be limited to the minimum required to reliably cycle the firearm and save a lot of wear and tear from overly aggressive cycling. Neat!

 A few other details... Can't help it, interesting firearm.

If you are familiar with an AR-10, or one of its derivatives, the SR-762 will have a familiar feel. The upper is hinged and locked down to its lower in the same fashion. The charging handle and bolt carrier are removed in the same manner.



While the core of the SR-762 is an original design and not a compilation of commodity parts, as is the case with many AR type firearms, there is a good deal of accessory compatibility. The SR-762 can use aftermarket buttstock assemblies, hand grips, trigger assemblies, charging handles, magazines, and compensators/flash hiders. A single, position marked, Picatinny rail runs from receiver top to gas block. The floating handguard is drilled and tapped to mount for accessory rails and accessories.



The SR-762 is supplied with 3 handguard grip panels, 2 accessory rails and all necessary hardware. Also included are a sight adjusting tool, 3 PMAG 20 round magazines and a really nice soft case that holds both firearm and accessories.

It's resting. It had a pretty busy day...

Today was cursory shooting, factory ammunition day, but it was informative. As an example, I made the comment that the rifle's bore volume, coupled with the 308 Winchesters moderate case capacity, was sufficient to minimize the negative effect the 16.125" barrel would have on velocity. I shot both Remington Express 150 grain ammo and similarly rated Hornady 150 grain ammo. Spec velocity is 2820 fps for the Remington ammo from a 24" test barrel. The same load chronographed 2,742 fps from the AR-762's 16.125" barrel, only a 78 fps difference with approximately 8" less barrel. The Hornady ammo closed that difference to 71 fps.



The SR-762 is probably the softest shooting 308 Winchester I've worked with. Keeping the regulator cranked down to the lowest reliably cycling setting, there only minimal recoil. Double tapping rounds and keeping shots close together was actually pretty easy with a bit of concentration to brush off the report. I tried stock position in and out, and it was comfortable shooting from either position. As far as accuracy goes, the Ruger SR-762 is definitely a sub MOA rifle, short barrel and all. Part 2 covers reliability of operation and live fire performance, including chronograph and accuracy data.

The nice part of living in the country is its gift of privacy and freedom. For anyone looking for America, it's there. Just far from noisy urban centers, angry issues and people who want to tell you how to live. The Ruger AR-762 is America. It's a defense weapon, it's a tool for law enforcement, it's a recreational target rifle, it's a hunting rifle. It's a tool. Fits right in with the TIG welder, or the compressor or the tractor. It is a symbol of self-reliance.

An Ingmar Bergman like SR-762 introspective... No. Not really

For a couple of weeks, a good deal of time was committed to working with the SR-762. It was shot with the supplied rapid deploy sights, red dot reflex sights and with a scope mounted as pictured. Both factory and handloaded ammo was fired. Most of the time the SR-762 was shot from a rest at paper targets, but it was also shot from standing and sitting positions at reactive targets. It's a rifle that is hard to put down... verbally or physically.

Form, fit and function

All controls are easily accessible and positive in operation. The handguard panels are a nice touch. They fill out the form of the handguard and they give it a comfortable shape/surface. The SR-762 was shot both with stock extended and collapsed. It is a really soft recoiling rifle that can be shot in either configuration, or in between, as needed. For anyone familiar with the rifle type, it has the balance of a high power guide gun and feels about the same when tracking a target with either metallic or reflex sights. It is a fast handling carbine. With a high magnification scope, and shooting from a rest, it has the steadiness of a varmint rifle.

Trigger

The trigger pull is classic AR and perfectly acceptable for a firearm intended for security or hunting applications. A little extra weight in a trigger pull is a bit safer and tends to take the heartbeat out of a trigger finger that follows a steep climb in rough terrain. Perhaps, at some point in time, Ruger will offer a long, heavy barrel version of the SR-762 similar in configuration to the SR-556VT with a two stage target trigger. In the meantime, if a hypercritical owner wanted a different trigger feel, the SR-762 is compatible with aftermarket specialty triggers.

Gas regulation

I started out making adjustments constantly, attempting to only open the regulator just enough for reliable cycling. It didn't take long before I realized the system is very forgiving and does not need that type of tending. Throughout the assessment period, the regulator was set and left on the #2 position. The only time I had to make a change was when shooting some Hornady Superformance ammo that for some reason seemed to like the #3 position, as did some very light handloads with relatively light bullets.



Routine Maintenance

The SR-762 is an incredibly clean operating firearm. No receiver covered inside and out with soot and gunk, or a bolt carrier that need to be constantly disassembled and solvent soaked to remain reliable in function. Without a direct feed of bore gas and residue, the rifle stays as clean as any bolt action rifle. Like any other AR type firearm, the aft takedown pin is pushed to one side and the barrel tipped down to facilitate bore scrubbing from the chamber side. Unlike traditional AR gas blocks and ports, the SR-762 gas regulating systems is designed for easy access from the muzzle side of the gas block and no special tools are required. I cleaned the rifle when received as a habit, checked the regulator and bore after each range session, but actually only cleaned it a second time when the project was completed. No cycling or other functional problems were experienced.

Live fire - Factory ammo

Federal Fusion and Remington Express ammo, both 150 grain, we used for factory ammo assessment; common, inexpensive and on hand. Hornady Superformance ammo was tried preliminarily, but Hornady had withdraw the product line from production so it was eliminated.



Ammunition Type Bullet
Grains 24"
Barrel
FPS 16.125"
Barrel
FPS Short Barrel
Difference
FPS
Federal Fusion 150 2820 2601 -219
Hornady Superformance 150 3000 2779 -221
Remington Express 150 2820 2742 -78

Remington appears to know optimal powder selection when it comes to the 308 Winchester. Most rifles chambered for the cartridge are lightweight and short barreled, rather than the having a 24" barrel which is standard length for ammo manufacturer testing and spec setting. The Fusion ammo 100 yard 3 shot groups ran between 1.0" and 1.1" from a rest, the Remington express shot 0.6" to 0.8". Different bullet weights and other brands could have shot differently, but I liked this result because both represent relatively inexpensive premium brand ammo of the type that would see frequent range and hunting use. The minimal velocity loss with Remington ammo was a pleasant surprise.

Live Fire - Handloads

Four flat base bullets were selected for handloading, two lighter loads for varmint and medium game, one midrange for large deer and black bear and one heavier weight for game with the body mass of moose and elk.



Bullet Weight
Grains Bullet
Length" Cartridge
COL "
Hornady SST 125 1.038 2.750
Hornady SP 130 0.940 2.690
Winchester PP 150 1.050 2.740
Sierra Pro-Hunter 180 1.210 2.800

Hornady offers the 125 grain SST as a component bullet and currently loads the 125 grain SST in Custom Lite ammo for Cabala's. It is intended to reduce recoil by being loaded to moderate velocity. Bullet construction is suitable for medium game with muzzle velocity in the 2,700 fps range which I thought would work well with the Ruger SR-762's 16.125" barrel.

As a last minute addition, some 125 grain AccuTip bullets pulls from 30 Remington AR ammo were included in the handload exercise. Rated at 2800 fps and accurate when fired from their parent ammo, it was an opportunity to experiment with a bullet with a short shank and minimal bearing surface.






Warning: Bullet selections are specific, and loads are not valid with substitutions of different bullets of the same weight. Variations in bullet length will alter net case capacity, pressure and velocity. Primer selection is specific and primer types are not interchangeable. These are maximum loads in my firearms and may easily be excessive in others. All loads should be reduced by 3%, and developed following safe handloading practices as represented in established reloading manuals produced by component manufacturers. Presentation of these loads does not constitute a solicitation for their use, nor a recommendation.





Cartridge: 308 Winchester
Firearm: Ruger SR-762 Max COL: 2.800"
Bullet Diameter: 0.308" Primer: CCI 200
Barrel: 16.125" Reloading Dies: Lee Precision
Max case length: 2.015" Group: Distance 100 yards - Three shots

COL and Capacity Load Data & Performance
Bullet Type Bullet
Weight C.O.L.
Inches Case
Grains
Water Powder Charge
Grains Muzzle
Velocity
FPS Muzzle
Energy Ft/Lbs Group
Inches
Hornady SST #3019 125 2.760 50.5 Re10x 42.0 2769 2129 0.9
Hornady SST #3019 125 2.760 50.5 Norma 201 48.0 2890 2319 0.7
Hornady SST #3019 125 2.760 50.5 RS TAC 49.0 3022 2535 0.9
Remington AccuTip* 125 2.775 50.9 Benchmark 46.5 2981 2467 0.8
Remington AccuTip* 125 2.775 50.9 Norma 201 48.5 2933 2388 0.9
Remington AccuTip* 125 2.775 50.9 RS TAC 50.0 3128 2716 1.2
Hornady SP #3020 130 2.690 51.1 Re10x 43.0 2865 2370 1.0
Hornady SP #3020 130 2.690 51.1 Norma 201 48.0 2894 2418 0.8
Hornady SP #3020 130 2.690 51.1 RS TAC 49.0 3002 2602 1.1
Winchester PP 150 2.740 49.9 Re15 47.0 2669 2373 1.0
Winchester PP 150 2.740 49.9 Norma 201 46.0 2681 2395 1.1
Winchester PP 150 2.740 49.9 RS TAC 46.5 2792 2597 1.0
Sierra Pro-Hunter #2150 180 2.800 47.7 Re15 44.5 2427 2355 1.0
Sierra Pro-Hunter #2150 180 2.800 47.7 Norma 203B 44.5 2438 2376 0.7
Sierra Pro-Hunter #2150 180 2.800 47.7 RS TAC 43.0 2543 2585 1.1
*Pulls from Factory 30 Remington AR Ammo



The 16.125" barrel was less of a velocity factor with lighter bullets. Plotting the diverging points of velocity between a 22" and 16.125" none of them are great. Comparing this data to industry handloading manuals where 22" barrels or even 24" test barrels are the norm, 125 and 130 grain velocities are essentially the same thanks to faster powder and low start pressures. At 150 grains, the velocity gap widens to 50 fps - 120 fps depending on powder selected, but differences flatten out. At 180 grains, the gap is only 50 fps - 80 fps. What might these look like in flight?



Hornady SST 125 Grain

Yards


0


50


100


150


200


250


300

Velocity - fps


3022


2865


2713


2566


2424


2286


2154

Energy - ft.-lbs.


2534


2278


2042


1827


1630


1450


1287

Momentum - lbs-sec


1.67


1.58


1.50


1.42


1.34


1.26


1.19

Path - in.


-1.5


1.1


2.6


2.9


2.0


-0.5


-4.6



Sierra Pro-Hunter 180 grain

Yards


0


50


100


150


200


250


300

Velocity - fps


2543


2436


2333


2232


2133


2038


1945

Energy - ft.-lbs.


2584


2372


2175


1990


1819


1659


1511

Momentum - lbs-sec


2.03


1.94


1.86


1.78


1.70


1.62


1.55

Path - in.


-1.5


1.4


2.9


2.7


0.8


-3.0


-8.9

With a 3.0 ordinate, both loads are point blank to approximately 250 yards. No range estimating from zero to a long ways out and lots of velocity and energy out beyond 300 yards. The 180 grain load, as an example, is pulling half a ton of energy out to 500 yards and remains supersonic out to 1,000. Less worrying about holdover distances and having to guess if you are looking at a small but faraway deer, or a monster buck at 50 feet. You know what I mean...

Good grief! Someone take this rifle away so I can get back to work...

OK, so I shot the SR-762 with open sights, a scope, a red dot sight. Light ammo, heavy ammo, slow fire, rapid fire... yet it seemed every time it quickly went to ambient cool, and it stayed clean... except for that little telltale brass smudge on the deflector. The finish showed no premature signs of handling, parts did not work loose nor did controls get sloppy. Whatever was supposed to click or snap into position did so.



I am sold on the gas driven piston system and I can't think of a reason this should be done any other way, other than to reduce manufacturing cost. I'd rather pay a modest amount more and get the better firearm, especially when you throw in Ruger quality and product backing. There will always be a few message board guys who think all ARs are the same and, with them, the exceptional features of this rifle will be lost. For folks who own, work on and shoot these types of rifles with frequency, the Ruger AR-762 will be viewed as an excellent firearm. For more details, stop by the Ruger site.