Ruger GP100 .327 Federal Mag. Revolver

By the Guns and Shooting Online Staff

Ruger GP100
Illustration courtesy of Sturn, Ruger &Co.

Back in the days when Colt and Smith & Wesson revolvers dominated the U.S. police market, William B. Ruger, co-founder and CEO of Sturm, Ruger & Company and one of the most brilliant gun designers in American history, wanted a piece of the action. His .22 autoloading pistol was the best selling gun of its type, as were his single action rimfire (Single Six) and centerfire (Blackhawk) revolvers.

In 1972, Bill Ruger introduced his "Six Series" DA revolvers, first the Security Six (fully adjustable sights, square butt) and then in quick secession the Service Six (fixed sights, square butt) and Speed Six (fixed sights, round butt). Like his previous SA revolvers, the new DA models were built around investment cast, medium size frames and used music wire (coil) springs throughout for enhanced reliability. A transfer bar to ensure safety against accidental discharge was incorporated in the ignition system. They were well made and affordable. Aimed straight at the police, military and civilian self defense markets, these were six shot, .38 Special and .357 Magnum (later 9x19mm and .38 S&W were added for overseas users), swing out cylinder, hand ejector, service style revolvers. Colt and Smith & Wesson were forced to recognize that there was a serious new player in the service revolver market.

Over 1,500,000 Six Series revolvers had been sold by the time the line was discontinued in 1988. The replacement for the Six Series was the GP-100, introduced in 1985 and the subject of this review. If the Six Series can be equated to the S&W "K" frame line, the GP-100 can be equated to the S&W "L" frame line. It is built on a larger, heavier frame designed specifically for the .357 Magnum cartridge.

Colt's Python, introduced in 1954, showed the world what an ideal .357 Magnum DA revolver looked like. The Python was built on a .41 caliber frame, not a .38 Special (.35 caliber) frame, for extended use with .357 Magnum cartridges. Medium frame revolvers, such as the S&W K-series and Ruger Six Series, developed problems if fed an extensive diet of .357 Magnum cartridges. They were strong enough to contain magnum pressures, but parts wear was accelerated. A Python size revolver was the answer. S&W merely copied the Python silhouette, top rib, full length barrel lug and all, inserting S&W lock work, but Ruger took the opportunity to further improve his DA revolvers.

The GP100 uses a larger frame than the Six Series and incorporates major changes. First is a triple lock cylinder, latched to the frame at the crane, as well as at the front and back of the ejector rod. Second is a stub (half size) grip frame that replaces a conventional grip frame, allowing the attachment of a one-piece grip of practically any size, shape or style. Grips don't attach to the GP100's grip frame, as with traditional revolvers, they slide over it and are attached by a screw through the bottom of the one-piece grip. Like the Six Series, but unlike Colt and S&W revolvers, music wire springs are used exclusively. The investment cast frame is solid (no side plate), most of the internal parts being attached to the trigger guard assembly, which is removed from the bottom of the frame. To swing out the cylinder, press in on a button mounted in the frame's left recoil shield.

GP100 revolvers are offered in alloy steel with blued finish or in stainless steel with satin finish, with adjustable or fixed sights, with or without full length barrel lugs and with various grip styles. The usual barrel lengths are 3", 4.2" and 6", although other barrel lengths have been produced as distributor specials. The GP100 was designed as a six shot, 357 Magnum (also accepts .38 Special) service revolver and .357 remains the most popular caliber. Recently, a seven shot version in .327 Federal Magnum caliber has been added, which is the subject of this review.

GP100 Features

  • Recoil reducing black rubber Hogue Monogrip
  • Triple locking cylinder
  • Patented grip frame accommodates a wide range of grips
  • Easy takedown of integrated subassemblies requires no special tools
  • Patented Ruger transfer bar ignition system
  • Heavy, precision rifled barrel
  • Included hard plastic case

Specifications (as tested)

  • Catalog number: KGP-4327-7
  • Model number: 1748
  • Caliber: .327 Federal Magnum
  • Capacity: 7
  • Material: Stainless steel; satin finish
  • Front sight: Ramp
  • Rear sight: Fully adjustable
  • Barrel length: 4.2"
  • Twist: 1:16"
  • Overall length: 9.7"
  • Weight: 40 ounces (empty)
  • 2013 MSRP: $759

The .327 Magnum cartridge looks like a skinny .357 Magnum and, because of the more slender case, Ruger was able to provide an extra chamber in the cylinder, making the .327 GP100 a seven-shooter. This gives it the same capacity as most single stack .380's or a Luger 9mm autoloading pistol, but the high velocity .327 Magnum shoots much flatter and hits harder.

Federal's .327 Magnum is one of the most under appreciated recent handgun cartridge introductions. Few shooters realize that it is the highest velocity, flattest shooting conventional handgun cartridge on the market. Specialized varmint and big game cartridges shoot flatter, but are designed for single shot pistols, not standard revolvers or semi-autos. The .327 Mag. is also one of our hardest hitting handgun cartridges. Federal factory load ballistics call for an 85 grain Hydra-Shok JHP bullet at a muzzle velocity (MV) of 1400 fps and muzzle energy (ME) of 370 ft. lbs. That is the same energy as standard pressure .45 ACP loads. The catch is that this is Federal's reduced power Low Recoil .327 load!

Full power factory loads can launch a 100 grain JSP hunting bullet at 1500 fps with 500 ft. lbs of ME from a 4" vented test barrel. This treads closely on the heels of the .357 Magnum and exceeds Federal's most powerful .40 S&W and .45 ACP +P loads. The trajectory of that load is such that a .327 revolver intended for use in the field can be zeroed at 100 yards without worrying about shooting over targets at shorter distances. It would be perfect, for example, for shooting jack rabbits and coyotes. Even fired from a self defense revolver zeroed at only 25 yards, that bullet drops just 4.5" at 100 yards. Pretty impressive ballistics for any handgun, especially a "little" .32.

The actual bullet diameter of .32 revolver cartridges is .312" and, because the .327 Federal is based on a lengthened .32 H&R Magnum case, any .327 revolver can also fire .32 H&R ammo. The .32 H&R Mag. has about the same power as standard velocity .38 Special loads, thus making it a useful understudy for the .327, as the .38 Spec. is for a .357 Magnum revolver. The .32 H&R is itself based on a lengthened .32 S&W Long case, which was in turn based on a lengthened .32 S&W (Short) case, so any .327 Magnum revolver can also fire these older revolver cartridges in a pinch.

Actually, because the popular .32 Auto uses .311" diameter bullets and a semi-rimmed case with the same .337" head diameter as the revolver cartridges, the .327 can chamber and fire the little .32 Auto cartridges. However, the ejector star of a DA revolver will not catch the .32 Auto's tiny rim, so the empties will need to be poked out individually by a nail or something similar.

Our new GP100 was supplied in a handy plastic carrying case. Inside were the usual accessories, including a gun lock and an instruction manual so larded with safety warning interruptions as to be almost unintelligible.

The barrel is a useful place to add weight for stability when shooting offhand, particularly with a 4" barrel. Our test revolver has a full length lug under the barrel and a solid top rib. The ramp front sight is pinned to the top rib. The front of the under lug slants rearward from the muzzle and it has a semi-squared-off shape, which is less attractive to our eyes than the seminal Colt Python's round version. Regardless, the .327 GP100 has a solid feel and we know it is a strong DA revolver. Weighing 40 ounces with a 4.2" barrel, it is obviously not a lightweight.

Guns and Shooting Online Editor Gordon Landers adopted the .327 GP100 reviewed here and made some simple modifications. First, he replaced the stock Hogue rubber Monogrip with a similar Hogue hardwood grip. Second, he installed a Wolff reduced strength spring kit and carefully polished the trigger, sear and hammer engagement surfaces. This lightened and smoothed the hammer draw and trigger pull. While the DA pull remained too heavy to measure on our eight pound (maximum) RCBS pull gauge, the SA pull was reduced to three pounds.

Then, he replaced the stock sights with Meprolight tritium night sights. This is feasible because the GP100's rear sight is screwed to the frame and the front sight blade is retained in its slot in the barrel rib by a pin that allows removal. Both the stock and Meprolight sights provide a Patridge type sight picture and there is no change in daylight accuracy, but the night sights glow in the dark, excellent for a home defense gun that might suddenly be needed well after lights out. The GP100 is one of the few revolvers for which tritium night sights are available.

Meprolight tritium sights for Ruger GP100
Meprolight tritium sights for Ruger GP100. Illustration courtesy of Meprolight.

As usual, we conducted our test shooting at the Izaak Walton outdoor range south of Eugene, Oregon. This facility has covered shooting benches and 25 yard target frames convenient for pistol testing. We fired five shot groups at slow fire bullseye targets from a Pistol Perch rest. Chuck Hawks, Gordon Landers, Rocky Hays and Jim Fleck, all G&S Online staff members, participated in the shooting.

Thanks to our friends at ATK, without whom reviews like this would be impossible, we had two factory loads available for testing: Federal Premium Personal Defense Low Recoil using an 85 grain Hydra-Shok bullet at a MV of 1400 fps and American Eagle with an 85 grain JSP bullet, also at a MV of 1400 fps. Having previously reviewed a small frame Ruger SP101 DA revolver and a big Blackhawk SA revolver in .327, we already knew that these loads are uncomfortable to shoot in the small frame SP101, but very manageable in the big Blackhawk. We were curious to see how the GP100 would handle the .327 Magnum.

25 Yard Accuracy Results

  • Federal Premium 85 gr. JHP factory load: Smallest group = 2-1/2"; Largest group = 4-7/8"; Mean average group size = 3.75"
  • American Eagle 85 gr. JSP factory load: Smallest group = 1-5/8"; Largest group = 2-1/2"; Mean average group size = 2.21"


This time, Chuck shot the smallest recorded group. We expected generally smaller groups than we actually shot, especially from the Federal Premium load. We got accuracy at the level of a good service autoloader, but less than we expect from a service revolver, which we feel should shoot into 2.0" or less from a benchrest at 25 yards. Perhaps the cold and rainy Western Oregon winter weather negatively influenced our performance. Basically, we all just wanted to get the shooting done and find someplace warm to slurp some hot coffee.

Our shooters agreed that the recoil of the GP100 was much more manageable than the hand slapping SP101. On the other hand, the Ruger Blackhawk single action revolver that we reviewed in 2010 proved to be the softest shooting of the three .327 Magnums that we have tested. (See the Product Reviews page.) The GP100 fell somewhere in-between, but closer to the Blackhawk than the SP101.

One factor in the Blackhawk's favor is its 5.5" barrel, which increases the sight radius and reduces the impact of the .327 Magnum's sharp muzzle blast on the shooter, compared to the GP100's 4.2" barrel. The .327 Federal is, after all, a true Magnum handgun cartridge and, like all magnums, it really deserves at least a 6" barrel.

Chuck criticized the Hogue hardwood grip that, like the stock rubber grip, has pronounced finger grooves that don't match where his fingers naturally fall on the grip. This finger groove grip amplified the gun's recoil for Chuck. If the GP100 were his revolver, he would fit Pachmayr Presentation rubber grips. On the other hand, Gordon was pleased with the hardwood grip. Rocky and Jim did not comment on the grip.

Otherwise, we agreed the .327 Magnum GP100 is a good revolver for personal or home defense and has potential for use in the field. The .327 cartridge is excellent and deserves more attention than it is currently getting from both shooters and the firearms media. A .32 handgun may not sound impressive, but we assure you the .327 Federal Magnum cartridge and the Ruger GP100 revolver is a potent combination.

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