October 31, 2012

Building a 10/17 Mach 2 Rifle

Building a 10/17 Mach 2

Since its introduction at the February 2004 Shot Show I have been patiently waiting for a .17 Hornady Mach 2 (.17 HM2) rifle that suits my exact and demanding needs. I have a wide variety of .17 (HMR) and .22 rimfire rifles and each has a specific purpose. I have my super accurate target rifles, I have those that are setup for spotlighting (make sure that this is legal in your state), those for general hunting, those for shooting offhand, and a “at ready” pickup 10/22 rifle. I really don’t have any that haven’t been modified in some form or fashion.

One of my greatest thrills in shooting is taking a stock gun and making it my gun! There is great pride and an extreme sense of accomplishment to be had when you “build your own”, even if you are just modifying an existing firearm. The best part is that you don’t have to be a gunsmith or even an experienced rifleman (After all, you are basically just changing parts).

Why am I waiting when I can just pick up my Brownells catalog and build the 10/.17 Mach 2 that I have been dreaming about!

Follow along, as I build my ultimate 10/.17 HM2 rimfire rifle.

Following closely on the heels of the immensely popular .17 Hornady Magnum Rimfire (.17 HMR) was the .17 Hornady Mach 2 rimfire round. Unveiled at the February 2004 Shot Show, the .17HM2 is based on a .22 long rifle stinger case that is necked down to .17 caliber to accept the 17 grain Hornady V-Max bullet. As many of you are already aware, the Stinger case is slightly longer than a standard .22 rimfire case and presents several problems to those who shoot it. This isn’t a concern to Mach 2 users because when necked down to .17 caliber it is dimensionally the same as a standard .22 long rifle case. The .17HM2 can be fired in any modern .22 rimfire rifle or pistol with a simple barrel change unless, it is a semi-automatic. A blow-back semi-automatic such as the Ruger 10/22 will require a modification to the bolt.

The .17HM2 is traveling almost twice as fast as the average .22 rimfire round (2,100 fps vs 1,050-1,080 fps) and therefore generates considerably more rearward force on the bolt. The added rearward thrust can potentially damage your receiver as well as interrupt the bolt timing that allows for proper empty case ejection as well as cycling a new round into the chamber. This issue has been addressed in two similar ways.

Volquartsen manufacture’s a .17 Mach 2 Heavy Bolt (#930-000-043) that is simply a heavier version of their standard 10/22 bolt. The heavier weight of the bolt slows down the rearward thrust of the bolt assuring that empty cases are properly ejected and the new rounds properly chambered. Power Custom solved the problem by adding the appropriate amount of weight to the Bolt Handle (#713-000-074) while still using the standard 10/22 bolt. Magnum Research also has a similar Custom Bolt Handle (#100-002-243).

Long Rifle Stinger Case

Courtesy Brownells

Left to Right: .17 Mach 2, .22 LR, .22 Stinger & .17HMR. The .17HM2 is based on a .22 long rifle stinger case that is necked down to .17 caliber to accept the 17 grain Hornady V-Max bullet.

In addition, Volquartsen supplies a hardened steel locking v-block for securing the barrel to the receiver. A tight and secure barrel lockup is necessary if maximum accuracy is going to be achieved. The factory receiver comes with a much weaker “cast” v-block that can crack or break when tightened tight. If you use a factory receiver replace the existing v-block with the Doug Koenig V-block (#388-122-001).

In addition, the Volquartsen Superlite receiver comes with a clear advanced polymer recoil buffer pin, replacing the factory steel bolt stop pin at the rear of the receiver. This is one of the best investments that you can make on any 10/22. After firing a round, the pressure generated slams the bolt rearward into the bolt stop pin. Its sole purpose is to stop the bolt from slamming into the rear of the receiver. Unfortunately, there is a price to be paid when “steel meets steel”. A steel-on-steel collision eventually causes wear and tear on the bolt stop pin and the bolt, but this energy is also transferred to the drilled receiver holes. Overtime, this will result in the elongation of these holes and damage to the receiver. Also, you have to consider the noise that this steel-on-steel collision generates. The 10/22 has a distinguishable metallic clang every time that a round is fired. The recoil buffer offers a much quieter cycling noise, so much in fact that you won’t believe this is the same rifle. If you have a factory receiver immediately replace the bolt stop pin with the Volquartsen Recoil Buffer (#930-010-000).

Our next component needed was an appropriate bolt. I choose the Volquartsen .17 Mach 2 Heavy Bolt (#930-000-043). This silver finished bolt is precision machined with extremely close tolerances accounting for its great reliability, tight fit, and accuracy enhancing properties. It is case hardened and smoothly ground so that it functions effortlessly. A fast lock time titanium firing pin is also included. With its integral and removable ergonomically-shaped bolt handle, it wasn’t necessary to purchase one separately.

The next and the most important component needed is a trigger housing/assembly. This is probably the most important decision you will have to make. The trigger is the life blood of any rifle and it is critical that you have a trigger that is light, with little creep (you always have creep in a semi-auto), and little or no overtravel. Trigger pull weight is a subjective matter. Some people (guilty as charged!) like a very light trigger pull and others want a heavier (but not factory heavy) trigger pull. Brownells have such a tremendous number of 10/22 trigger parts that is difficult to decide how to build one. Let’s break it down in two categories. Category one consists of completely assembled custom trigger housings/assemblies. With these all you have to do is attach them to the receiver with two pins and you are ready. You don’t have to decide which trigger components to use since they all have state-of-the-art custom parts already installed. About the only decision you have to make is which one best suits your personal needs. This is primarily based on its trigger pull weight and the components that it contains. Brownells has three of the best custom trigger housings available from JARD, STI, and Volquartsen.

The Volquartsen Superlite Receiver

Courtesy Brownells

The Volquartsen Superlite Receiver (#930-000-028) is precision CNC machined from a solid billet aircraft-quality aluminum. This receiver comes with a full-length Weaver-style base already installed.

Item by item, they are JARD 100-002-145, JARD 100-002-146, JARD 100-002-147, and JARD 100-002-148. The STI items are STI Match and STI Super Match. From Volquartsen, 930-000-001 and 930-000-003.

For this project I decided on the STI Super Match Trigger for several reasons. One, it was an easy “no worries mate” assembly that required only the pushing of two pins into the receiver holes. Two, it was the only trigger that was a two-stage trigger.

I am used to shooting two-stage triggers in my AR-15s and this now just comes naturally. In general, semi-automatics require greater pull weights, to be safe, than bolt actions. Basically, the purpose of a two-stage trigger is to divide pull weight into two separate actions, thereby effectively lowering your trigger pull weight. A lighter trigger gives you greater control and enables you to shoot better groups. The STI 10/22 trigger has an 8 oz first stage take up. The trigger reaches this stage and then stops until you begin further squeezing of the trigger. At an additional one pound of pressure, the trigger will fire. Due to the light trigger pull weight, you probably will not even feel the difference between the first and second stage. Most people are used to such heavy factory trigger pulls that they normally just “pull” too hard on the trigger. My advice is to practice trigger control by very gently pulling on the trigger until you can feel the 8 oz take up movement.

One of the shortcomings of the 10/22 receiver is that it offers no way to properly clean the inside of the barrel unless you take off the barrel each and every time. This isn’t advisable because of the possibility of the barrel’s point of impact shifting if the barrel isn’t repositioned and tightened in the same manner with the same amount of force. Plus, you have more wear and tear on your receiver and barrel faces. The other choice is to clean your barrel from the muzzle end. Not a good idea because it is very easy to damage the rifling at the end of the barrel. This will certainly result in larger more erratic groups, depending upon the severity of damage. It does dramatically help to use a Dewey Muzzle Guard (#234-014-102) for a factory barrel or (#234-014-202) for a .920” diameter barrel). Brownells has come up with a third option that maximizes cleaning while minimizing barrel rifling damage.

The STI Super Match Trigger

Courtesy Brownells

The STI Super Match Trigger is an easy assembly that required only the pushing of two pins into the receiver holes.

Brownells designed a 10/22 Receiver Drilling Jig (#080-917-000) to solve this problem. This jig allows you to drill a .257” hole in the rear of the receiver that is perfectly in line with the barrel. Now you can easily pass your .17 caliber cleaning rod through the receiver and properly clean your barrel. To insure proper cleaning techniques, use in conjunction with a brass Dewey Muzzle Guard (#234-802-022). Don’t worry, anybody who has a drill can perform this simple task. This is a simple L-shaped metal jig that has a silver-looking hardened drill bushing in which the drill bit is placed. The jig has two holes that are drilled and tapped to perfectly match the two receiver holes. These two holes are more appropriately named trigger guard retaining pin holes because this is where the trigger housing/assembly attaches to the receiver. For brevity, I will just refer to these as receiver holes. Place masking tape on the outside surface of the jig in order to prevent the metal to metal contact of the receiver and the jig which could mar the surface of the receiver. The jig comes with two allen head bolts, two nylon washers and one spacer tube.

The nylon washers are placed on the bolts next to the head so that the nylon washers are between the receiver surface and the bolt head to prevent marring of the receiver. The purpose of the spacer tube is to prevent the crushing of the receiver walls as the front receiver bolt is tightened down. If you notice, the area around the front receiver hole is open and has no support while the rear hole is fully supported. Place the spacer tube inside the receiver and line it up with the front receiver hole (holes since each side of the receiver has a hole). This is the hardest part that I encountered. I believe that the walls of the Volquartsen receiver are thicker than the Ruger factory receiver and therefore made it more difficult to place the spacer tube between the receiver walls. If I used this jig exclusively for Volquartsen receivers I would slightly grind the spacer tube until it fit perfectly between the receiver walls. Since I couldn’t do this, I just had to spend a little extra effort.

Courtesy Brownells

The Brownells 10/22 Receiver Drilling Jig (#080-917-000) allows you to drill a .257” hole in the rear of the receiver that is perfectly in line with the barrel. Now you can pass your .17 caliber cleaning rod through the receiver and properly clean your barrel.

After the spacer tube is properly lined up on the front receiver holes (meaning both sides of the receiver) place the bolt with the nylon washer next to the bolt head completely through the hole a spacer tube coming out the hole on the other side of the receiver. Do the same for the rear bolt, except there is no spacer tube needed. Now you simply line up the bolts with the drilled and tapped holes on the jig. Start your bolts in the jig threads by hand to be sure that they are aligned straight and don’t cross thread. You can tell by touch. If your bolt easily goes into the jig’s threads then you are properly aligned. If you meet resistance when you first start turning the bolt stop, back out the bolt and try again. Tighten your bolts with a 5/32” allen wrench until they are tight. Do not over-tighten them.

Now that your receiver is affixed to your drilling jig, place it in a vise. The Brownells Multi-Vise (#080-000-019) is the perfect vise for gun work and one that you will use over and over again. To prevent marring the surface of your receiver and jig, use Brownells Rubber-Faced Vise Jaws (#080-827-000). These magnetic jaws simply slip over your existing steel jaws and can be removed as need be. Next make sure that the jig is plumb (level) by using a level. I like the Starrett Cross-Test Level (#827-505-690). It has two bubble vials at right angles that allow you to check for squareness and plumb level at the top at the same time. Now you are ready to place your F (.257”) Drill Bit (#891-306-257) in your drill (corded or cordless) and coat with Do Drill Oil (#083-007-016). The application of this oil on your drill bits and taps will help lubricate them and thus reduce heat buildup which can discolor and distort the metal being drilled. The hardened drill bushing in the jig will align your drill bit with the receiver. Before starting to drill, make sure that your drill is level. Today, most drills have built in levels. If not, use your Starrett level. Remember, don’t use too much force when drilling, the object is not to see how fast you can drill a hole, but how accurately.

After drilling you are ready to begin tapping. Tapping is the process of cutting threads in a hole. We will use a 5/16”-18 Plug Tap (#891-516-182) to thread our hole. I placed our tap in our bar style Tap Wrench (#395-312-088). This tap wrench has a handle on each side to help balance the torquing forces and reduce lateral forces. One handle is threaded so that it can exert pressure on the square head of your tap when it is placed in the center of the tap wrench. Before tapping, I make sure that I lubricate the tap with Do Drill oil.

Courtesy Brownells

This shows the receiver and jig in the vise ready the hole. The hardened drill bushing in the jig will align your drill bit with the receiver.

Next place the tap in the hole and make sure that the tap is perfectly straight before hand turning it clockwise. After a few turns the threads should be formed and the end of the tap will be inside the rear of the receiver. Now carefully turn the tap counter-clockwise until the tap clears the hole. To protect the threaded hole and keep any possible debris out of your receiver thread a 5/16”-18 set screw (this can be found at your local hardware store) into it. Simply remove it when you clean your barrel.

Assembling Receiver and Trigger Housing _The next step is to assemble the bolt in the receiver. The Volquartsen .17 Mach 2 heavy bolt consists of the bolt body, bolt handle, and a recoil rod with a spring that slips over it. It is necessary to remove the bolt handle before placing the bolt in the receiver. The bolt handle has a small rounded indentation at its base. A spring loaded detent contacts this indentation and holds the bolt handle in place. Remove the handle by simply rotating the handle so that the detent is no longer in contact with the bolt indentation and simply pull the bolt handle straight back. The next step is to place the bolt in the same position that it will go into the receiver.

Note that the recoil rod and spring go in the milled slot on the side opposite where the bolt handle goes. The pointed end of the recoil rod goes into a recess at the rear of the receiver. The opposite end of the recoil rod goes through a small hole at the front of the bolt. The hole is large enough to allow passage of the recoil rod but not the spring. This action compresses the spring thus allowing the bolt to “slide back and forth” inside the receiver under the recoil of a fired round. With the recoil rod and spring in the proper position on the bolt, place the pointed end of recoil rod on a hard surface and slowly compress the spring until the opposite end of the recoil rod enters the hole at the front of the bolt. Continue to compress the spring until about 1/2 to 3/4 inch of the rod extends past the end of the bolt. Approximately 3/4 inch of rod will be seen when the spring is completely compressed.

Hold in position and firmly grasp the end of the rod with the thumb and forefinger of your other hand. Now place the bolt between the two rails of the receiver. The pointed end of the recoil rod will come in contact with the recessed hole at the rear of the receiver. At this point, slide the bolt all the way back until it comes in contact with the rear wall of the receiver. This action compresses the spring even more. Now push the bolt upwards until it comes in contact with the top of the receiver. Now you can gradually release the bolt and it will be in its proper place in the receiver. The next step is to push the bolt handle into its hole. You can feel and hear when it “bottoms out”. Slowly turn the handle until you can feel the detent come in contact with the indented hole on the bolt handle. Now the handle is locked in place.

Courtesy Brownells

Use a brass hammer and punch to drive the receiver pins in place.

To remove it, simply rotate the bolt handle until the detent pin is no longer in contact with the bolt handle recess and pull it straight out. To remove the bolt, place your thumb at the rear portion of the bolt where it raises up (increases in thickness) and push rearward until it comes in contact with the rear of the receiver. Place the forefinger of your other hand in front of the bolt and pull it towards you until the bolt is removed from the receiver. It sounds simple and it is, but practice until you are proficient at installing and removing the bolt from the receiver. Don’t be discouraged if you couldn’t do it the first time; I couldn’t either!

Next install the clear polyurethane recoil buffer pin in the hole located in the rear of the receiver. It is located directly above the rear receiver hole. Gently tap the recoil buffer in place with your nylon/brass hammer and pin punch (Using a pin punch dramatically lessens your chances of marring your receiver. You want to use a pin punch which is slightly smaller in diameter than the recoil buffer.) until it is flush with the receiver surface. Next I use a black permanent marker and paint the recoil buffer ends so that it blends into the receiver.

Our next step is to install our trigger housing/assembly on the receiver. As stated before, there are two receiver holes (technically trigger guard retaining pin holes) to which the trigger housing attaches. Simply line up the corresponding holes in the trigger housing with the receiver holes. Using a Nylon/Brass Hammer (#818-600-100 or #818-600-075) and an appropriate size Pin Punch (#080-553-000) gently tap the provided pins until they are flush with the surface of the receiver. Now that the receiver buildup is completed, we are ready to install the barrel.

To see more photos of the project, click here:

http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?p=0&t=1&i=994