The GP 100 and SP 101

Ruger’s Versatile Belt Revolvers

by Mike Cumpston

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While the popularity of the revolver has been largely eclipsed in the official realm, interest in the revolver as a defensive and recreational tool remains strong. It seems that revolver lore doesn’t sell many gun magazines and the internet discussion boards pile up many more hits on their semi-auto forums. Nevertheless there are marked advantages to the cylinder gun. These benefits are recognized by both new and seasoned shooters who have enough interest in the subject to develop real skill with the sidearm. These are the shooters who are neither TACTICAL nor COMBAT nor prone toward stuffing excess loads of natural fertilizer into inadequate containers. They do have a pronounced tendency to actually hit what they are shooting at.

In the 1980s, before the mass migration of defensive shooters to the semi automatic pistols, the search for a durable.38/ .357 service revolver was in full swing. Smith and Wesson came out with the intermediate L Frame family and, in 1987, Ruger introduced the GP 100. The GP was a fairly thorough -going redesign of the already tough and durable Security Six family. It was followed soon after by the downsized SP 101- an obviously sturdy snub .38 that seemed to beg for high performance loading. When several experimenters began hot loading for the SP and converting it to the relatively short .357/125 loads, Ruger stretched the frame and chambered it for the full range of .357 factory rounds.

The search for the long-lived .357 package continues to the present day and has become a two-pronged effort. The Rugers have proven quite durable and Smith &Wesson has recently strengthened their traditional revolvers. At the same time, according to recent Speer Loading Manuals, the industry has reduced the approved operating pressures of the cartridge to 35,000 psi. This is a significant move as the loading manuals of only a few years ago regularly listed loads in the 40-47,000 psi range. Speer’s top listed loads now turn in .38/.44 level performance. Conversely, many current factory loads are significantly more energetic suggesting that the 35,000 psi figure is not set in concrete.

The GP/SP series has proven a resounding success. The heavy, solid frames and relatively massive lock-work and the rigid front crane lock combine to defy the traditional characterization of the Revolver as a fragile instrument. Available evidence suggests that they are holding up well. A few shooters report that they have shot their GP’s out of fix but many more report many thousands of rounds through the guns without noticeable deterioration. I have encountered a couple of credible reports of cracked barrels or forcing cones in the SP 101 series but top gunsmiths report few problem guns coming through their shops. Jack Weigand, American Pistolsmith Guildsman, is a strong advocate of the GP 100. He has developed protocols for removing excessive end-shake proving that even the Rugers can develop the situation. I have found only one second hand Ruger with significant wear. It was an early Security Six with the early signs of failure to carry up. Second hand shelves and gun show tables abound with competitive designs showing significant use- related wear. This is not the case with the GP and SP revolvers. The database here is sparse, as few of these handguns are available for observation. Their owners seem disinclined to trade them off. Either they lack the fickle nature of most gun enthusiasts or are so enamored of the Rugers that they will not let go of them.


Besides the robust construction, these Ruger small and intermediate frame revolvers have a number of features in common to recommend them to the enthusiast. The sights on both fixed and adjustable variations are highly visible and usable by shooters who need close-up vision correction with many handgun sights. The synthetic grips do much to tame the recoil of the magnum rounds. The grip angle and trigger reach of both the GP 100 and the SP 101 work well for a large number of shooters. An unadvertised but desirable aspect of the double action lock-work places the cylinder in full lockup well before the hammer reaches full cock. This, combined with the tactile clue of locking bolt engagement, permits rapid, accurate two-staged double action shooting. This pre-timing arrangement was considered a desirable feature on the old Smith and Wesson Safety Hammerless. It is also being used in advertisements for the new Taurus CIA (Carry It Anywhere) snub.

An interesting aspect of this is that it is relatively easy to eat the center out of a Standard NRA target center at 25 yards firing one handed and double action and to do so in the traditional rapid fire cadence. This, of course, defies the practical/tactical wisdom about loosing fine motor control under stress- but it’s a heck of a lot of fun. The SP101, fired in this manner will generally land most of its shots in a six to eight inch group at the same distance. Fired two handed with the trigger pulled in an uninterrupted manner, the SP turns in a most un-snub-like performance at twenty five yards and beyond.


Common complaints in ref: the Ruger actions in general usually start with the observation that the actions are neither as light nor as smooth as those found on say, Smith and Wesson. This is less true than in the past. Ruger’s usually come from the box with six or more pounds of single action trigger pull. Recent Smiths, in deference to legal concerns, now also approach that weight. The Ruger Double action has a much different feel than the Smith and Wesson but is generally very usable without modification. One caution is in order regarding double action cycling of these revolvers. After firing, the trigger must be allowed to return fully forward. Short stroking the trigger can lock up the action preventing a rapid second shot. When this occurs, releasing the trigger is all that is necessary to regain normal function.


Like the earlier Security Six revolvers, the GP/SP are of solid frame/modular construction and can be dismounted to major part groups without tools. They even put a little pin in the left grip panel to capture the mainspring on its strut. Disassembly closely follows the instructions in the Booklet and with a bit of practice, becomes quite easy. The necessary practice for this to occur may not be forthcoming as it is seldom necessary to break the revolver down for cleaning. Here occurs another cautionary note:

Upon reassembly, it is necessary to make sure that the pin that locks the action module into the frame is actually engaged. Otherwise, the revolver will try to dismount itself at some inopportune time. Best check is to tug on the trigger guard to make sure it’s really in place.

One task, seldom undertaken and rarely necessary, is removal of the cylinder from the crane assembly. Since this involves removing the frame latch and the ejector rod, it is a scary proposition until actually undertaken. Then, like most of the Ruger processes, it becomes transparently easy. After either removing the grips or the entire crane assembly, observe the relatively large hole in crane in front of the cylinder. Stick a small tool-( I used a large caliber, unbent paper clip) into this hole and depress. Then shove the through-pin out of the side of the frame and start picking parts out. This single pin, visible with the crane /cylinder assembly locked in battery retains the latch, the ejector rod and they cylinder itself. Everything goes back together in reverse and just won’t fit if you put them pointed the wrong way.

A sure sign of the popularity of this revolver system is the availability of after-market springs to fine tune the trigger pull. The Wolff Spring Kits offer a couple of replacement trigger return springs and a selection of main springs of varying weight. The object is to select a combination that will give reliable trigger return and ignition while reducing the trigger pull(s). They are easy to install. First. Disassemble the unloaded revolver in accordance with manual instructions. Carefully remove the mainspring from its strut and replace with the Wolff Spring. This is the tricky part since, if you don’t carefully capture the spring and retaining plate, one or both will go zing-whining off into the distance to become lost or put your eye out.

The Trigger Return Spring also drives the plunger that holds the trigger guard to the frame. It is not under load and will not spring away when released. Simply push out the little pin at the back of the trigger guard, pull out the plunger and change springs.

Since you now have the revolver apart, this is a good time to do some conservative polishing of the bearing surfaces in the lock-work. This will probably not do nearly as much to smooth the overall operation as a good dose of shooting and dry cycling.

Web sources suggest that double action reliability is not certain with the lighter mainsprings. Shooters in the know often say that reliable ignition begins with the ten pound weight. Some also report sluggish trigger reset with the lighter (eight pounds) of the two trigger return springs.


During the late ‘70s and early ‘80s I had a 6” Stainless Security Six which I used for everything from shooting bullseye targets, to early metallic silhouette competition to greasing jackrabbits to bouncing drunks at local honky-tonks. It was good and I never wore it out. I did finally trade it off. In the early 90’s I had a 6” GP 100 with the short under-lug. It would handle the full-gorilla handbook- sanctioned loads of the time and I was a fool to trade that one off too.

In 1996, after ten years of struggle, we managed to get a Concealed Handgun act through the Biennial, Bicameral, by-Jupiter Texas Legislature. One of the first things I did was to go get me a 2.25” SP101. This was and is my answer to the “ carry-it-anywhere” question and, by virtue of being a revolver, has completely taken over that role from my Walther PPK. It is a flame thrower with the Gold Dot 125, which leaves the barrel in the Middle 1200 fps range.

Not too long after that, I decided I had to have a stainless 4” GP 100 and it, also is a frequent carry gun. Until recently, I left the factory springs in place finding that I could stroke the double action with a satisfying level of accuracy and do credible work with the single action which settled in at five pounds after considerable shooting. The trigger pull and the 4” tube provided reasonable excuses for the occasional stray shot out of the 25 yard bull. I feel very well equipped with this 4” as it will drive the Speer 125 grain Gold Dot to 1441 and deliver groups ranging from 1.1” to just under 2” at 25 yards. It hardly kicks at all. This revolver has become so smooth with handling, that I tried the light 8# trigger spring from the Wolff Kit. This dropped the single action pull to 2.5 pounds with snappy trigger re-set.

The tantalizing accuracy of the 4” gun led me to go looking for a new and permanent 6” short lug. While my first two revolvers are extremely popular and obtainable, I seem to be the only customer who doesn’t prefer the full-lugged version of the six-inch. My dealer didn’t have any and neither did the Ruger factory. My new Hamilton Bowen rear target sight and Wolff Spring kit languished in a drawer while Ruger cobbled up a supply of the short-lugged GPs.

Immediately upon arrival and before any shooting, I installed the heaviest(12 pound) main spring and the heavier (10 pound) trigger return and followed up with some heavy-duty dry firing. The single action pull dropped from six plus pounds and stabilized at 3 pounds two ounces where it remains after some rather intensive shooting and dry cycling. The Double action pull is nice.

The revolver fulfills its anticipated role as a target arm. A wide variety of target velocity loads are accurate in the 1.1- 1.4” range at 25 yards. I have to work hard to drop the occasional double or single action offhand shot out of the NRA bullseye. My first-ever group was a 1.2” five shot spread with the 125 grain Gold Dot that also has the good grace to rip out of the 6” tube at an average 1530 fps. My second ever group was a 1.7” cluster with the 125 Grain Hornady XTP over 21 Grains of 296 and a WW Magnum Primer. It is pretty closely equivalent to the Speer load averaging 1541 fps. It leaves the .357 SIG wallowing in the ballistic dirt. Prior to wrapping up this report and after firing about 500 rounds of assorted loads through the 6” GP, I sat down and fired three consecutive five round groups with three very different loads. As close as I could read the caliper the 25- yard groups went 1.11”,1.18” and 1.14”

As mentioned, the shorter members of this triad are carried very frequently. The SP101 travels in various holsters according to the dress code of the moment. The 4” usually rides around in a Sparks Summer special with some kind of un-tucked shirt covering it. The 6” is also carried concealed in an old Bianchi spring-loaded X 2100-shoulder rig. This is more comfortable than you would think.


All this aside, it is the recreational attributes of these revolvers that makes them fun to own. The SP101 is pretty much a pure weapon but the other two are versatile and perform well with a number of loads. Here a while back I delved into various loading of the .38/ .357 wadcutter with the 4” GP. The long -seated Meister Swaged Hollow base design over light charges of Bullseye turned in a multi- group average of 1.85” with about a one tenth inch accuracy advantage going to the loads put up in .357 cases. The same loads from the 6” reversed the trend grouping .357 loads into 1.5” and .38 case loads into an average of 1.3.”

Similar group averages were demonstrated with factory approximate loading of 3.5 Bullseye and several 158 grain bullets including a flat point cowboy design and the Hornady Swaged 158 lead SWC. Some produced better accuracy from .38 cases and others grouped better from the magnum case. The only load that didn’t work at all well in the magnum chamber was a flush seated bevel-based wad cutter loaded in .38 Special cases. The 6” gun would throw three inch groups with these.

It is notable that, with the faster burning powders (Unique and Bullseye), the velocity difference between the four and six inch GPs is very slight. It favored the longer barrel but you could load the bullet between thumb and fore-finger and thump it across the sky screens fast enough to make up the difference. The same is true of the difference between .38 and .357 cases with the same load. The slight velocity and extreme spread advantage went to the short rounds.

In the spirit of the times, I decided to try out one of the kinder and gentler loads now infesting the loading manuals. I decanted the maximum (no need to work up to this one) listed 12.5 2400 into a magnum case topped with the 158 Hornady XTP. This is about 1.5 grains shy of reaching the base of the bullet and is not generally a good thing with 2400. I did a batch of these with CCI 500 Standard Primers and another with WW Magnum primers. (yep, it says for Magnum Loads on the box.) There was a difference. The standard primer loads did 1219 (6”); 1167 (4”),and: 1080(2.24”). The WW Magnum Primed loads clocked 1258, 1223, and 1194 from the descending order of barrel lengths. Here again, except for the short SP 101, you could heave a dead cat across the sky screens fast enough to make up the difference.

The real kicker comes in with a not unexpected gain in load consistency and fewer unburned powder flakes with the magnum primers. The maximum extreme spread with the standard primer was 108 fps while the magnum primers reduced this to 74 fps. Boy! From this it was easy to infer that the lousy standard primed load would group crummy while the more consistent Mag primed rounds would probably shoot pretty good groups. Imagine my surprise when the inefficient standard primer load turned in a 1.11” smallest group with a three- group average of 1.3” and the magnum primed groups averaged out at 1.5”. If an “expert” didn’t have a chronograph, he would never be aware that he was shooting a lousy load unless another “expert” told him that this was the case!

These Rugers were designed to stand up to immoderate firing with full loads back when everybody seemed agree that the maximum working pressure of the .357 was 40-47,000 pounds per square inch. Nevertheless, it would be useful to find a load of moderate power that would perform well on some of the tougher small varmints. The Hornady swaged semi-wadcutters had proven accurate at nominal .38 velocities so I ordered some of the hollow point version of this bullet. I loaded these bullets over 6 grains of Unique for mid to high 1,000 fps averages from both GP100’s. I was getting fifty five caliber expansion on beef brisket at 25 yards. There was no visible leading from the 6” and little with the 4” but the 1.9” - 3.5” groups wouldn’t do. “ Combat! Accuracy” only counts in horseshoes and hand grenades. Dropping the charge to 5.5 Unique in .357 cases delivered 957 fps from the 6” and 927 from the 4” GP. Three 25-yard groups from the longer barrel went 1.6. 1.8” and 1.1”. Expansion on the grocery store meat was just as impressive as with the six-grain charge. These lead hollow points are visible more needle-nosed than the solid semi-wadcutter version and the walls around the hollow point are pretty thin. They should thump down a ‘coon or jackrabbit with good repeatability.

Last I heard, CorBon was using a 4” GP 100 to prove out their top performing loads and it soldiers along digesting them without complaint. Back in the good (bad) old days of 40,000 + psi handbook loads, Speer was using a Security Six for the same purpose.

The Ruger GP/SP line lacks much of the cache attached to the century-old designs of Colt and Smith and Wesson. Nevertheless, they are solid performers and will go the extra mile.

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