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Ruger Ultimate Bullseye Upgrade, Part One: From workhorse to thoroughbred, the prolific and popular Ruger Mark I and II rimfire pistols are readily converted into top Bullseye performers.

Several years ago while plinking at our local sportsman's club, I ran into fellow shooters who competed in NRA Precision Pistol, often known simply as Bullseye shooting. They invited me to join the sport with them and explained to me the rigors of what it took to play the game. Not really having a Bullseye-grade pistol, I didn't know where to start. I went to a local old-time gun shop and talked to the owner behind the counter. He recommended something like a Hammerli, S&W 41, Walther, High Standard, Benelli, or a Pardini. Having recently purchased a Ruger Standard from my pastor for $150, I asked if it could be suitable and he remarked that it was well within the capabilities of shooting Bullseye, however, its trigger system would make it more difficult to be a strong competitive pistol. That said, the journey started. Since then, I have successfully built dozens of Rugers that I see weekly on our Bullseye line in the hands of the top shooters competing with great success.

I must preface this presentation with the caution that these pistols when completed are not picnic plinkers for the whole family to play with. I cannot repeat that strongly enough. When finished, these pistols will easily keep up with the most expensive European-made models. You will see throughout that this requires a tremendous amount of attention to detail. Some of it is seemingly quite minor, however, all of the "itty bittys" can add up to an "I gotcha."

There are three serious disclaimers. First, before undertaking any procedures in the following text, it is your responsibility to have a complete working knowledge of the firearm and its fire control system. Second, you are responsible for all the work that you perform. This article is for educational purposes only and no liabilities are implied or expressed. Finally, the techniques and procedures I present are mine alone and may not work for you. It is up to you, your judgement, and your clients to determine what is best and most appropriate.

Frame Types

It is always advisable to make sure the Ruger model that you have is indeed in an A-100 frame. The easiest way to identify the frame is to see which side the magazine button is on. It should be on the left side. While it is possible to upgrade a model A-54 frame (which has the magazine button on the right-hand side), those models are very difficult to get target grips for or much else in the way of aftermarket goodies. A-100 frames became available in late 1970. Mark I pistols manufactured after then and all Mark II pistols should be A-100 frames.

This information is intended for Ruger MK I and II pistols only. The Ruger 22/45 is a polymer framed pistol and is too flexible for safe upgrade. The MK III, though a fine pistol, has internal passive safety mechanisms that must be preserved and tend to limit the final performance level. Unfortunately, the new MK IV has a magazine disconnect like the MK III predecessor. I have not had opportunity to engage a serious look at the MK IV, however, passive magazine safeties must, by law, be fully functional when they leave your shop, so be forewarned. The MK I and MK II platforms avoid this area of concern.

After establishing that you have an A-100 frame, make sure the firearm is clear and empty with the magazine out of the gun. I will choose to start with the upper, or the barrel receiver assembly as it's known. This is the part of the pistol with the serial number on it. Check to make sure that the gun is clear and empty again and insert a dummy snap cap for a dry fire. This can be done with an empty, fired case, a commercial snap cap such as from Tipton, or an appropriately-sized yellow wall anchor such as from Hillman Fasteners available from a hardware store at about $0.06 each. Ruger does claim dry firing does not hurt this rimfire pistol, however, why take the chance?

I will list manufacturer part numbers with the Mark I first, followed by the Mark II. Unfortunately, Ruger rimfire pistols are much maligned for difficulty in disassembly and reassembly for routine cleaning. This is unfortunate, as once successfully executed, it is an extremely easy firearm to disassemble and reassemble. One must take into consideration one part I refer to as the "devil's strut," which is the hammer strut (A10 or A01000) that hangs off the hammer proper. With that in mind and while holding the dry-fired pistol in your off hand, pull out mainspring housing latch (A7 or A00700) out of the back of the grip and use it as a handle to pull the entire assembly down and out of the gun with your strong hand. Set this assembly aside but not far as the mainspring housing latch can be used as a handy tool in the successful disassembly and reassembly of the pistol.

The bolt assembly is ready to come out. I have found it most advantageous to retain the bolt in the closed position, rotate the muzzle up, and shake the pistol downward stoutly. This tends to keep the "devil's strut" from interfering with the sear spring stop pin (A26-3 or A02603). The hammer should rotate rearward and allow the bolt to slide out the rear. If for some reason it stops, it's because the tip of the "devil's strut" has stubbed out on the sear spring stop pin that retains the tail of the sear spring. No problem, as a tool capable of freeing the hammer is the mainspring housing latch. If set at 90 degrees to the mainspring housing assembly, it makes a pretty handy tool for moving the hammer forward enough to free the strut.

The strut should clear the cross pin, allow the hammer to rotate completely reward, and the bolt and dummy cap should slide right out. With the bolt in hand, the gun can be broken down. Go to a padded area, hold the muzzle up in one hand and a soft mallet in the other (a clean hockey puck works really well), and tap against the front of the frame assembly to move the body of the gun away from the barreled receiver. The frame will fall off, though some are much tighter than others. At this point you have a cylindrical receiver attached to the barrel, a bolt with all of its parts on board, and the lower with fire control and magazine assemblies together, along with the mainspring housing assembly.

Next is the barrel/receiver assembly. If yours is not drilled from the factory (many are not) I recommend obtaining a genuine Ruger three-hole scope mount and line it up as if it were factory drilled with the 6-48 mounting screws. I made a template from a copy of a factory drilled barrel and use that. This also allows the original rear sight assembly to stay in place.

To do this accurately, remove the rear sight and use the rear sight dovetail cut out as the square area of the gun to find top dead center. After determining TDC, center punch the last hole to the rear with a spring-loaded punch. Drill and tap that hole, mount the rail, then center punch, drill, and tap the next hole. Remount the rail and repeat for the last hole. If all has gone well, the rail is indeed at TDC and there are no stresses between the mounting screws. With the rail in place, the original sights look right down the middle of the rail screws. I have had problems in the past with rails shooting loose in a couple of years of use. Bullseye shooters don't seem to understand this is common and it is their responsibility to check these things routinely. I always ask if they ever intend to remove the rail and if the answer is no, I Acra-Bed the rail and apply blue Loctite 242 on the screws to attach it to the barreled receiver. This seems to end the problem of loose rails. As a last and final step on the barrel receiver assembly, I bores cope the bore and the chamber because I generally find it necessary to slightly radius where the feed ramp enters the chamber with the lightest touch of a Cratex buff.

Working Internals

Moving on the bolt itself, it has a lot of room to make things better. Remove the recoil spring assembly from the top of the bolt. I generally pull everything out, including the extractor which itself can really be a nuisance. To remove the extractor, first remove the firing pin stop (A35-B or A03500) running left to right. Some bolts have the extractor plunger hole drilled all the way through to the firing pin stop hole and some do not. After removing the firing pin stop, remove the firing pin (Al3 or KA01300), rebound spring (A39-1 or A20000), and rebound spring support (A39 or A03900). I then attempt to remove the extractor (A22 or KA02200), extractor plunger (A25-J or A02510), and extractor spring (A25-J1 or KA20300). Putting a small screwdriver behind the shoulder of the extractor plunger and pulling it rearward should reveal the tail coming through the hole where the firing pin stop resides. This will actually become a handy port for cleaning later. I use a very small jeweler's screwdriver to catch the shoulder of the extractor plunger and pull it back as far and as hard as I can as I try to lift the extractor itself out of the bolt. The extractor should lift straight out to the side of the bolt. The plunger and spring are pretty cooperative and generally don't try to get away. However, be prepared should this not be the case.

I then begin work on the extractor itself using a small, flat surface plate with wet or dry sandpaper for finish work. 600-grit sandpaper with some quality stoning oil produces good results. I do both sides of the extractor, making sure that any burrs or uneven edges are gone, and finish with a red India stone to lightly radius the edges. Then, I sharpen the extractor hook tip and bevel the bottom portion of the hook and inside corner. These pistols feed from a magazine straight up and need to allow the rim of the case to slide between the extractor hook and the bolt face. It is important that this transition is smooth. I realize that many will argue the extractor is only valuable in removing a live case from a charged chamber. While I cannot argue that point, I have found that a tight extractor greatly reduces the number of alibis. Following this, I take a thinned popsicle stick and wrap the same oiled 600-grit paper around it, running that into the extractor's channel. It is surprising how sharp the burrs can be in there.

Next is the firing pin. I lay it sideways on 600-grit paper or flat stone and remove any irregularities on both sides, followed by an India stone to radius all the edges. After that is completed I wash everything down. I'm a big fan of Ed's Red and I'm pretty sure everyone knows what that is.

Fortunately, putting the extractor back in is really not as difficult as getting it out. Press inward and to the rear and it should snap in underneath the extractor plunger. I usually examine the rebound spring, which has a tendency to be pretty stiff. I replace the mainspring with a softer one and need to ensure solid detonation on rim fire cartridges. Since these pistols will not be used for casual recreational purposes, our concerns of firing pin detonation from muzzle impact should be considered minimal. The rules at our matches and most others are strict about safe gun handling, so I choose to keep the tension on the rebound spring minimal but definitely present. I generally trim a coil or two off the rebound spring and leave the rebound spring support alone. I then reassemble the rebound spring support to rebound spring and the firing pin to the bolt. There should be some resistance to the firing pin and it should return to the unfired position with finger pressure after releasing it. Despite being lightened, I have never seen any type of marks on ejected, unfired live cases after the bolt has been driven home.

I then push the firing pin slightly forward and replace the firing pin stop. I do not change the spring in the recoil spring assembly (A38-3 or KA-57) though I do pick which side of the yoke is going to be the upper portion and which part is going to be the lower portion. This yoke would be the rearmost "fork" of the recoil spring assembly that abuts the bolt stop pin (Al or A00l00). The front semicircle that engages the slot in the bolt proper rotates 360 degrees and doesn't have a specific orientation. Here, I remove some of the metal at the rivet point of the yoke. With a small relief at this point, installing the mainspring housing assembly along with the bolt stop pin up through the frame and bolt will be much easier on final installation. Install the recoil spring assembly into the bolt.

Next up is the lower grip assembly, which for some reason does not have a serial number on it. This is where the gentleman friend behind the counter was correct about the fire and control mechanisms and problems in the Ruger series. Our objective here is to remove as much "out of tolerance" as possible. To this end, there will be very few things that we don't get involved in.


Look at the relationship between the trigger (A12 or A01200), the disconnector assembly (A11 or KA011), the sear (A19 or A019010, the hammer (A18 or A01800), and the safety (ASC or AN53-100) you're starting with. As you have just a lower in your hand, replace the mainspring housing assembly. This will have the bolt stop pin sticking up through the hole in the back of the frame. You will need to align the hammer ("devil") strut with the mainspring plunger (A25-1 or KA02509). When the hammer is cocked, there will be pressure against the hammer as it engages the sear (A19 or A01901). This will allow you to see what your starting point will be when we get to this section. Not all Rugers are the same.

Cock the hammer and allow the sear to engage the hammer notch. This is all quite visible from the top. Put the safety in the "on" position, guard the hammer with your off hand in case it should release. Pull the trigger firmly and see how much movement there is between the sear itself and the hammer hook with the safety on. Unless it is unlike any Ruger I have ever seen before, there will be a great deal of movement of the sear and the hammer hook, yet it will not release the hammer. The sear will creep back under the hammer hook when releasing the trigger, common for stock Rugers. We'll look at this in detail later but I bring it up because you'll be removing many of these parts and need to see where the starting point is and what has to be done to turn this into a Bullseye-ready pistol. Proceed once you have accessed and established the amount of excess tolerance in your pistol's fire control system.

I begin at the very front end of the lower where the trigger pivot pin (A34 or A03400) goes through. There will be a slightly different procedure Mark IIs as they have a bolt lock stop and a slightly different trigger pivot pin. Check your Ruger's trigger to find if the left-to-right wobble of the trigger in the frame will be excessive. This isn't an issue for most people but it may be an issue for a Bullseye shooter. The main goal is making sure every trigger pull and reset is as identical as possible. Achieve a good fit by removing the trigger (A12 or A01200) and hammer pivot pin (A26-5 or A02605). Then remove the safety, hammer assembly, hammer bushing (A26-E or A02505).

Be careful not to allow the safety detent plunger (A02511) or the safety detent spring (A20200) to fall out of the safety assembly. The MK I uses the same parts but are not shown in its exploded view. MK I and MK II safety bodies are not interchangeable due to the differing bolt lock systems. The sear will flop rearward and relax.

Move the disconnector assembly (All or KAOll) upward, freeing the trigger spring plunger (A25 or A02508) and trigger spring (A34-2 or A20400). The disconnector assembly is still trapped by the trigger. On the MK I series, remove the trigger pivot pin (A34) by removing the tiny trigger pivot lock washer (A34-1). This isn't fun but you won't likely need the lock washer again as a new "oversized" trigger pivot pin should provide a good interference fit to the frame on assembly. On MK lIs, depress the trigger pivot retainer (KA 04200) to free up the trigger pivot pin (A03400). Its removal will free the trigger and bolt stop (AN-37) as well as the disconnector assembly..

You can install an aftermarket trigger now. Most of them come with pre- and post-travel stops, however, I've found the holes there to be excessive due to manufacturing tolerances. I use factory trigger drill pre- and post-travel stops myself. The post-travel stop is straightforward, made by drilling a centered #43 hole and tapping it out with a 4-40 tap. The only tricky part is drilling the pre-travel screw. I secure the trigger in a drill press vise, using a carbide #43 drill bit (they are sharp and stiff) to drill at an angle through the front corner of the trigger, being careful not to run into the trigger pin hole, then tapping to 4-40. This sounds much more difficult than it is. I find 4-40 set screws of various lengths at our local hardware in the "Hillman Fastener" section. This provides a trigger that I know will fit and overt ravel adjustments that I can work with.

The part that really makes the difference is the trigger axle pin as this can cause excessive slop between the trigger and pivot pin as well as between the frame. I have found using the largest gauge pin that just fits through is a 0.1575" minus, provided it's perfectly round and well finished. It fits factory triggers well and tends to be a little too large for the frame, developing a nice interference fit when finally installed. I am currently experimenting with thin shims on these upgrades but cannot accurately report on that yet.

Moving on to the parts of the trigger, I chuck up and polish the trigger spring plunger. I buff the inside of the trigger spring plunger hole in the trigger with a small buff in my Dremel tool and install a Wolff reduced-power trigger return spring. I replace the disconnector assembly with the reinforced CNC machined unit from Volquartsen (#VC2DN). While not inexpensive, these are extremely effective in reducing disconnector flex, which is quite detectable during a slow-fire stage of fire and is a real deal maker when it comes to the final finished product. The only thing I do to this Volquartsen part is smooth the outboard side with the 600 paper and break any sharp edges. I then take a buff in my Dremel tool and buff the inside of the frame proper where are the disconnector resides to a high shine.

As we leave the front portion of the lower, let's look at the essential piece that makes a Ruger an effective Bullseye pistol: A dirt shield. While a relatively unusual piece of thin material, I have seen pieces of aluminum beverage cans used as well as other thin metals. I fabricate a dirt shield that keeps the products of combustion and other debris from falling down into the trigger spring plunger assembly. This area is one of the major downfalls of using a Ruger as a Bullseye pistol and protecting it is a must.

To construct a shield, I use a piece of 0.005 stainless steel shim stock and trim a tab and shield piece that fits between the barrel and lower assembly, sealing out dirt from the top of the trigger and trigger spring plunger assembly relatively well. I generally fit these as I go so there really aren't any specific dimensions as to how to make them. The photographs here demonstrate how I make mine.

The shield is trapped by the interference fit created by the front lower lug to the barrel. If it is installed correctly, the left-to-right bend in the shield will be in line with the rearmost edge of the feed ramp.

Gage Pins

Moving to the rear, when I do a "full monty" job I replace the hammer pivot pin and the sear pivot pin (A26-8 or A02601) with "oversized" selected gage pins. When working with the Mark IIs, it is not possible to replace the hammer pivot pin as it has a head on it that holds part of the bolt stop assembly in place when the grip is installed. These axles are fitted as large as possible and still run smoothly in the sear and hammer bushing.

A Ruger factory trigger generally will take a 0.1575- gage pin as a very good fit. Volquartsen triggers have larger axle pivot holes and must be tried for fit. With gage pins for sears, OEM sears usually fit well with 0.128- gage pins and Majestic Arms sears usually fit well with 0.127+ gage pins. For hammer bushings (applicable on MK I series) Tandemkross III will usually take 0.157- gage pins, OEM MK III will usually take 0.157+ gage pins, OEMMKI andMK II usually take 0.1575+ or 0.158- gage pins. Majestic Arms will usually take 0.158+ gage pins.

Getting to the meat of the matter, the sear, hammer, and safety arrangement on the Ruger series will require very careful adjustment. Anyone attempting to do a Bullseye-grade trigger job on a Mark I or II pistol must realize how the fire control system and safety works. I find the lack of concern with safety in aftermarket parts to be upsetting. Ruger's safety design is excellent, however, it must be closely monitored to make sure it is working as designed.

While looking at your assembly after taking the barrel off, there is a disconnector assembly connecting the trigger and the sear. Cocking the hammer causes the sear to fall into the hammer notch and the hammer is retained from going forward. If the disconnector is in the down position, activating a trigger does nothing. If the trigger bar is in the up position it will engage the sear and the hammer will be allowed to fall. The safety on this design is actually a hook that goes over the front left edge of the sear and locks it mechanically into the hammer notch.. I would be surprised if you didn't see some substantial movement in the sear/hammer interface earlier. I cannot emphasize proper operation of this arrangement enough. You are going to remove metal from the sear contact surfaces but maintain positive engagement. This is where the rubber meets the road.

I cut my own sears using a Power Custom Series One stoning jig. After setting the stoning fixture to match the angle of the sear that came out of the gun, I reduce that angle in very minor amounts until I get a trigger pull I am happy with. The engagement must remain positive. As a final way to smooth this up and maintain a great deal of surface area while not having it be detectable is to use a white ceramic stone and quite a bit of elbow grease to finish the engagement surface of the sear proper to a mirror-like shine. Do not attempt to use a buff as a shortcut as the sear edges must be maintained as sharp and square. The white ceramic stone will do the job, it just requires patience and the aforementioned elbow grease. It doesn't really remove metal as much as it really improves surface quality. I do not alter the cut in the hammer notch. If you are not comfortable or do not have the tooling to recut your sears consistently, buy aftermarket matched sets. Volquartsen and Majestic Arms make very nice sets of match-grade sears and hammers.. Whether using original or aftermarket parts, polish the tip of the hammer strut. This strut is frequently poorly finished and benefits from a high polish on the radius tip.

Next time we will go into complete detail as to how to accomplish final result of creating a Bullseye-grade Ruger.

by David Allen Dumeah
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Title Annotation:TECH TOPICS
Author:Dumeah, David Allen
Publication:American Gunsmith
Date:Nov 1, 2017
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