Ruger Ultimate Bullseye Upgrade, Part Two

Last issue we completed a tear down of a Ruger Mark I or II pistol for Bullseye and started in on improving the trigger. We’ll finish that and wrap up our build. Use of aftermarket sears and hammers can be a good way to improve a Ruger’s trigger but does not remove concerns regarding safe function. It is necessary to have the sear pulled into the hammer notch securely, removing all internal tolerances when the safety is engaged.

Aftermarket match-grade parts generally have some sear movement when the trigger is pulled and it’s important that any movement be adjusted out. I have found that minimal movement here creates two levels of trigger pull. There is the original which is set by A 5/32" drill shank followed by a smack with a four-ounce hammer can do the trick. the hammer and sear during normal reset.

The other is the secondary level—which can be dangerously light—set by the pull of the trigger with the safety engaged and moving the sear slightly away from full engagement of the hammer notch, creating an unpredictable trigger let off. This is totally unacceptable. Make sure when the safety is engaged it actually pulls the sear into the hammer notch firmly, removing all of the remaining tolerances of the fire control system.

The way to do this is to take the safety out and put a 5/32" drill shank through the hammer pivot pin hole, set it up in a vise so that the top hook of the safety is the highest part, and give it a good smack with a four-ounce hammer. What we are essentially doing is bending the hammer hook closer to its axle point. If you are careful and don’t use anything too heavy, it does not take much. It most likely will raise proud metal on either side of the tip of the safety which needs to be filed or stoned off.

Done right, it makes the safety engage a little on the tight side. If it is too tight for the safety to engage comfortably as you pull that button down, gingerly take a slim pillar-type file and lightly remove a stroke or two off the front edge of the notch. Reinstall and check, continuing until you can pull the safety down while firm pulls on the trigger don’t generate any motion at all between the sear and the hammer. That’s where you want to be.

If using aftermarket parts you should be able to get a relatively accurate trigger weight at this time. I have seen very few sear/hammer arrangements that were commercially made that didn’t need some safety adjustment. For those who decide to cut their own, it is a trial-and-fit situation. Most leagues set rules regarding minimum trigger weights for competition. They are reasonable and attainable. Remember, YOU are responsible for every trigger that leaves YOUR shop.

It is not uncommon to slightly back cut the sear to reduce creep if necessary, however, a little goes along way. Again, you will need to make sure that the safety is working as described above.

The next item to be attended to is be the mainspring housing. Retained in the mainspring housing is a mainspring latch, mainspring detent ball (A41 or A04100) ball bearing, a mainspring (A20-1 or KA20100) and a plunger (A25-1 or KA02509). We will replace the heavy mainspring with a Wolff reduced power mainspring. This reduces trigger pull substantially while not compromising rimfire ignition. Unfortunately, this is a very challenging procedure.

Drive the mainspring housing latch pin (A26-9 or A02602) almost all the way out. Be sure to have a stout rag handy as the ball bearing will come out with The heel release extension with trimmed thread protector. great force and is frequently lost. It is not a bad idea to have a few extras around. The size they take is 7/32" and local hardware stores won’t likely have extras in that relatively odd size.

However, this size is used in quality front wheel hubs of Italian bicycle wheels and a call to the local bicycle shop may prove fruitful. As a last resort, they are available as a Ruger/Brownells part, but who wants to slow the job down that much? I remove the remaining plunger and spring and set them aside. I then modify a buff by using a plastic .22 caliber cleaning brush wrapped with apiece of linen and covered with rouge compound. Run that buff on the inside of the mainspring housing channel.

Chuck up the mainspring plunger proper and buff it also. After all the buffing is done, wash all the parts thoroughly and began reassembly. Reassembly Reassembly is rather challenging, so pick a time of the day that works for you. The way I successfully replace the mainspring plunger spring and ball bearing is in a rubber-jawed vice.

Clamp the mainspring housing horizontally in the vice and install the plunger with anew Wolff reduced-power spring and begin to slide the tail end of the mainspring housing latch in its appropriate channel. The ball bearing needs to go back in. If you had the misfortune of removing the mainspring housing latch pin completely, put it in a pin vice and slightly taper one end to assist getting it started into the mainspring housing.

To begin the reassembly, take an ordinary hex screwdriver with no bit installed and slide it over the stub tail of the mainspring housing latch. This provides the ability to steer the lever where needed. With the tail of the mainspring housing latch trapped in the slot of the mainspring housing by the rubber vise jaw liner, start the mainspring detent ball with your non-dominant hand. Pinch the ball bearing up against the bottom of the mainspring coil and catch it with the edge of the takedown lever.

You will be required to balance the pressure with your hex drive screwdriver. A slightly smaller slave pin will help in positioning the mainspring housing latch and hold it there. When you get the mainspring housing latch to its appropriate location, try to tap the mainspring housing latch pin back in. After achieving alignment, fin-

Remove enough for a smooth release but don’t go through. ish driving the mainspring housing latch pin flush and restake the ends as necessary. This is a good time to check the staking on the bolt stop pin (A26-2 or A02602). I bring this up here because I have seen them come loose. When and if the bolt stop pin works loose, it is almost impossible to remove the mainspring housing assembly without serious cosmetic damage to the frame. The last and final area I work on is the magazine.

There are several very good tutorials online concerning proper tuning of Ruger magazines, however, avoid removing any metal unless it is absolutely necessary. I usually buff the feed lips extensively on the exterior and use a Dremel to carefully buff the feed lips on the internal sides. I also buff the front internal surface of the magazine frame where the bullet nose rides. This area tends to accumulate bullet lubricant that impedes reliable feeding. Shinier is better.

It is necessary to address the channel that the follower button rides in on the MK II models due to the larger button and bolt stop function. Remove all burrs with apiece of sandpaper (400-600 grit) over a 60-degree cut block of wood or use a Cratex buff in a Dremel if you have one. I then smooth out any casting burrs on the plastic follower proper. Grips If the customer decides to go with a Volquartsen target rubber grip, make accommodations to allow easy magazine removal.

This is an extremely popular grip and most likely one you’ll encounter. To facilitate easy magazine removal, modify the magazine latch (A5 or A00501) by drilling and tapping a vinyl-covered stainless steel stud in the base all the magazine latch. It is possible to buy a complete magazine latch with extension as an after market part, however, with Rugers one has to remember that the upper barrel and lower grip assembly are held together by a partial interference fit and a partial lock fit.

The barrel and the lower may not necessarily engage at the same depth from gun to gun or even within the same pistol. The magazine latch determines the height of the magazine feed lips in the barrel receiver assembly. If the magazine latch you have is working well, it’s best to keep that one in the gun. Unfortunately, I have seen Rugers that "high feed" with all magazines, allowing the empty case leaving the chamber to become knocked off prematurely by the secondary feed lips of the magazine.

This is something that is frequently overlooked and much maligned. To put the magazine latch stud in, don’t remove the magazine latch as it is difficult to remember the spring orientation to get it back in. It can be

put in a couple of wrong ways and sort of work. I count four slots from front to back in the serrations, center and punch it, and make a blind hole with #29 drill on the angle pictured here. I thread the blind hole with an 8-32 end tap, cut a stub of 8-32 threaded screw, and Dremel a screwdriver slot in the end. Be sure the stud is long enough to get a hold of, but short enough to not protrude past the base of the installed grip.

Add a blue Loctite, snug the stud into the blind hole, and slip a thread protector trimmed to length over the exposed threaded stud. To finish, the magazine itself must be modified slightly where the plastic base of the magazine meets the magazine frame proper. There will be an edge of proud steel that will catch the magazine latch if it is not relieved, making digging the magazine out of the rubber grip quite challenging.

I use a band sander and slightly taper the back tip of the magazine frame so it will be flush with the plastic base when finished after removing the base plate and internals. When this has been accomplished and the magazine is in place, a pull and hold on the magazine latch stud will allow the magazine to fall freely from the magazine well. Continuing reassembly, move on to the barrel receiver assembly. Place your dirt shield in the recess of the barrel and rotate to its proper location.

Place the barrel on the lower, being sure that the tongue of the dirt shield is inside the magazine housing and not slipping through the cut out in the trigger guard. Align the barrel and the lower as accurately as possible and tap them together. To check to see if you are close, insert the bolt stop mainspring assembly from the top down and see if it will go all the way through easily. If it does not, either the barrel is not back far enough on the lower or it is not clocked properly.

Make the necessary adjustments so that the bolt stop pin will drop in and out easily. Place the hammer in the fully cocked position being careful not to let the hammer ("devil’s") strut get caught on the sear spring stop pin. Should it get caught—as it so frustratingly so does—use the mainspring housing latch to push the hammer forward, freeing the hammer strut from the sear spring stop pin to allow a retry. Tip the pistol in such away that the strut falls away from the sear spring stop pin.

With the hammer in the fully cocked position, install the bolt assembly. Sometimes, the bolt may act like it is bumping into something solid and does not want to go fully forward. Should this happen, gently rotate the bolt clockwise and counterclockwise slightly while pressing forward and it will find its way home. With the bolt fully forward, move the hammer into the fully fired position. To do so, rotate the pistol muzzle down and pull the trigger.

Using the mainspring housing latch, push forward on the hammer proper. The hammer should move forward. Take the mainspring housing assembly and install the bolt stop through the bottom and into the barrel receiver upper. This is where that slight dimple I recommended you Dremel into the yoke rivet of the recoil spring

assembly comes into play. The final seating of the bolt stop up through the bolt and recoil spring assembly will be much easier. The final step, and frequently the most frustrating, is closing the mainspring housing latch successfully. The least frustrating method requires knowledge of what is going on under the mainspring housing assembly. You are trying to capture the tip of hammer strut in the cup of the mainspring housing plunger. You can easily misalign these.

Tipping the muzzle upward and looking to see the strut free hanging vertically downward is a good start. Slowly close the mainspring housing and if the strut-to-plunger is properly aligned, you’ll feel a springy resistance while seating the housing before closing the mainspring housing latch. Manually cycle the bolt to confirm assembly. This is a good time to check safety function as well as the final trigger weight using dummy snap caps.

This weight may be different than the weight achieved while you were reworking the fire control section.. This can be attributed to a flaring of the lower when attaching the upper. Be sure that your trigger weight is at an acceptable safe level. The preand post-travel stops can be adjusted to suit. Be careful to not over adjust the pre-travel stop as the system will not reset if you adjust it too precisely.

The reset on these models is quite audible and I generally am quite generous with the adjustments to ensure 100% reliability. Even with that dialed in, it is far superior to the original arrangement. A touch of some fingernail polish to hold the set screws and you’re done. Mark I builders who choose to use the Volquartsen rubber grip will have to make a small modification in the grip to make it 100% usable with that unit. The grip panels on the MK I and II are designed to hold the hammer pivot pin in place.

Since there is A1 Bolt stop pin A26-3 Bolt stop pin pivot A20-1 Mainspring A25-1 Mainspring plunger A41 Detent ball A7 Housing latch A26-9 Housing latch pivot A38 Recoil spring assembly A13 Firing pin A35B Firing pin stop A39-1 Rebound spring A39 Rebound spring support no Volquartsen MK I grip, there will beavoid in the grip to accommodate the bolt stop thumbpiece (A04700) of the Mark II. This void will need to be filled in to assure the hammer pivot pin does not drift out to the left.

I A22 Extractor A25-J Extractor plunger A25-J1 Extractor spring A100 Grip frame/trigger guard A5 Magazine latch A26-1 Magazine latch pin A27-7 Magazine latch stop pin A12 Trigger A34 Trigger pivot A34-1 Trigger pivot lock washer A34-2 Trigger spring A25-H Trigger spring plunger Ruger Mark I (Speci ications subject to change without notice) A11 Disconnector complete A18 Hammer A25-5 Hammer pivot A26-E Hammer bushing A10 Hammer strut A26-4 Hammer strut pin ASC Safety complete A19 Sear A26-8 Sear pivot A31-A Sear spring A26-3 Sear spring stop pin routinely use three pieces of closelycut credit card super glued together and super glued into that rectangular spot.

It works very well. As a rule of safety, I always explain to the customer that this par-

Ruger MK II (Speci ications subject to change without notice) AN-37 Bolt stop assembly A00100 Bolt stop pin A02602 Bolt stop pin pivot KA011 Disconnector assembly KA0220 Extractor A02510 Extractor plunger KA20300 Extractor spring KA01300 Firing pin A03500 Firing pin stop A01800 Hammer A02505 Hammer bushing A02605 Hammer pivot ticular pistol is no longer a picnic plinker. It is designed for formal Bullseye competition in a controlled environment.

Should it begin to double, discontinue using the pistol immediately and bring it back for service. I personally have never had one come back in. Ruger factory parts are of exceptional quality and durability. Thoroughly check over your work.

Safely test fire and A01000 Hammer strut A00501 Magazine latch KA20100 Mainspring A04100 Mainspring detent Ball A00700 Mainspring housing latch A02602 Mainspring h’s ing latch pin KA02509 Mainspring plunger A20000 Rebound spring A03900 Rebound spring support recheck your work, including any changes that may have occurred after the test fire, including the final trigger weight.

It is a relatively protracted procedure, however, the final results area unit that will easily keep up with the expensive, finicky, and difficultto-get-parts-for European specificuse .22 competition pistols of the day. As always, safe shooting.

AG AN-53-100 Safety assembly A02511 Safety detent plunger A20200 Safety detent spring A01901 Sear KA02601 Sear pivot pin A02603 Sear spring stop pin A01200 Trigger A03400 Trigger pivot pin KA04200 Trigger pivot retainer A20400 Trigger spring A02508 Trigger spring plunger American Gunsmith Reader Services 1.