A Second Bolt And Barrel For Bolt Actions

Over the past 16 years I have added bolts and scores of barrels to a good number of switchbarrel rifles. This has included bolt selection from the three common bolt face sizes ranging from .223 Remington, .308 Winchester, and the larger magnums. Most of these have been fitted to Model 700 or Model 40X Remingtons and long and short Savage actions. This worthwhile rifle revision enhances its usefulness and increases overall value. Costs are usually commensurate with parts selection and needs.

Adding a second bolt and barrel requires precise headspacing. For example, if a random barrel from another rifle is used or has combined use with another rifle, the new bolt must be precisely fitted and headspaced to the secondary barrel and action. I accomplish this by reducing the bolt locking lug length. As an example, I’ll cover a very adaptable application whereby two previously headspaced barrels, chambered in The bolt comparator, as designed and made by author, precisely measures this dimension.

This information is useful in fitting a second bolt or barrel to a rifle. As anew bolt is fitted, contact here can take place before locking lug contact, producing an incorrect headspace reading. different rifles for the .300 WSM and 7mm Remington Magnum, along with an altered magnum size bolt, are added to an existing rifle which has a .308 size bolt, and barrels chambered for the .25-06 Remington and 6.5-284 Winchester.

The action is bedded into a target/varmint stock as well as an alternate standard weight stock to serve as a lighter weight carry rifle. One action and scope serves all barrels. In the case of 700 and 40X Remington actions, the bolts are very

close in dimension as measured from the rear of the locking lug surfaces to the face of the bolt. This will allow some barrels to be exchanged between rifles and still be within SAAMI headspace tolerance. Such close bolt tolerance offers the gun owner a feature whereby a barrel from one rifle can be used on another rifle if the cartridge headspace is correct.

Thus, when adding anew bolt, where its dimension is longer, it can be a relatively simple matter of shortening the span between the locking lugs and bolt face of the longer bolt to headspace the respective cartridge. This procedure has enabled me to actually take previously headspaced barrels and use them alternately between different rifles by machining the bolt lugs in attaining proper headspace.

Bolt Alteration Procedure This work requires the experience of a well-qualified gunsmith or shop machinist skilled in precise machining tolerances along with a good knowledge of rifles.

Where an existing barrel is headspaced to a given rifle to be used in another rifle along with the new bolt, I measure each The forward surface of the locking lugs are placed firmly against the chuck jaws to permit precise replacement as the bolt is removed and checked for proper cartridge headspace. bolt from the back of the locking lug to the bolt face to determine if the new bolt is longer than the primary rifle bolt.

If it is longer by even a few thousandths it allows me to shorten the new bolt lugs to the required length. However, if the secondary bolt is shorter, this procedure cannot be successfully accomplished while

borrowing a barrel from another switch barrel rifle. In this case the barrel shoulder would need to be set back or the chamber lengthened in order to acquire precise headspace. This precludes the use of such barrels in more than one rifle. Another way of checking this out is to put the trial barrel on the action and trying a headspace gauge or new unfired case. If the bolt doesn’t close, you will be in business.

To select a secondary bolt I use a bolt comparator of my own design and made by attaching laterally opposing jaws to a cut-down micrometer. This instrument accurately measures the distance from the bolt face to the back of the locking lugs and makes the match between a second bolt or barrel much easier. This is particularly useful where barrels are used from another rifle as I have commonly done. Take-off barrels that fit one’s needs may be a viable choice too.

A point of caution when installing a second bolt is to be sure there is ample clearance at the rear of the bolt handle in the receiver or stock cutout. Any contact here before the locking lugs make receiver lug contact will result in a false headspace, and must be corrected for proper clearance. With the secondary bolt and barrel selection made, it is time to move on to actually altering the locking lugs.

As the bolt is placed in the lathe, bolt run-out and locking lug symmetry are checked with a dial indicator attached to the lathe carriage. A Remington Model 700 bolt can be held coaxially between the lathe chuck and live tail stock center. The 0.145-inch shroud, forward of the locking lugs, conveniently allows this. Alive tailstock center aligns the bolt perfectly as it fits the rear bolt hole.

Lathe setup should find the properly sharpened lathe tool bit making just light contact with the locking lugs with the graduated carriage stop on zero. Then, while cutting, advance the tool bit as little as a thousandth of an inch at a time. In the process, the bolt is repeatedly removed from the lathe and headspace is checked. A good check to see how things are going is to close the bolt on the headspace gauge while closely observing the gap between the partially screwed on barrel shoulder and rifle receiver.

A feeler gauge will show a close approximation of bolt lug over-length in this way. Finally a fully torqued barrel at normal axial preload is required to arrive at correct chamber/cartridge headspace. I usually use anew unfired case to check headspace as I move along. An unfired case will allow the bolt to be closed before a Go headspace gauge is accepted. As the bolt is returned to the lathe, I make sure the forward surface of the locking lugs is squarely against the lathe chuck jaws.

There is no turning back if the locking lugs are shortened beyond normal cartridge headspace. Don’t carelessly cut two or three thousandths of an inch from the bolt lugs when you mean to take just one thousandth. In the work that I have described here, I removed 0.007 inch from the bolt lugs, which allowed me to add a magnum bolt to this Remington Model 700 rifle. This is but the thickness of two sheets of paper used to print this article—less than the thickness of a common playing card.

Yet, this enabled me to add the two pre-headspaced barrels in calibers .300 WSM and 7mm Remington Magnum to the Model 700 rifle. The pre-existing bolt for this rifle was already headspaced for the 6.5-284 Winchester and .25- 06 Remington cartridges in a heavy Bell and Carlson target/varmint stock. All barrels could then be used in either the standard weight stock or heavier varmint/target stock with the respective bolts, resulting in one of the most versatile switch-barrel rifles of its kind.

On successful completion of the work, barrels must be properly identified. Here I stamp the car- American Gunsmithing Association

Where a barrel fits two rifles, this is included as well. tridge name, rifle make and serial number, brand of barrel, and rifling twist. If the barrel fits more than one rifle, all information is stamped accordingly. Considering the many variables involved, there is always some degree of trepidation as to just how well the much-worked-on rifle would perform. This was quickly dispelled as I shot two five-shot groups under a half-inch with the .300 WSM and 0.70 inch with the standard weight 7mm magnum barrel.

Primers remained totally flush with the case head on each cartridge after firing. Used rifle bolts are usually available through gun parts outlets like Numrich Gun Parts Corporation (gunpartscorp.com, Jack First Gunshop (jackfirstgun. com, or Quicksight Gun Shop New rifle bolts are often difficult to obtain. Conclusion The addition of secondary bolt, barrels, or stock to a switch-barrel rifle can be accomplished by a qualified gunsmith or good machinist.

The procedure is well worth considering as it stands to greatly increase both the usefulness and value of the rifle. You may end up with one of the most revered rifles you’ll ever own. AG From top, a standard weight stock with the altered magnum bolt headspaced for both the .300 WSM and 7mm Remington Magnum. Along action bolt headspaced for .25-06 Remington and 6.5-08 Winchester cartridge bedded into a Bell & Carlson target/varmint stock.

The Model 700 action is precision bedded into each stock with Brownells Steel Bed. In use, barrels can be switched in less than 10 minutes as the scoped action remains in the stock. 300 WSM with cartridge headspacing accomplished by shortening the locking lugs 0.007". A finer big game carry rifle may be hard to find. A 7mm Magnum barrel is also pre-headspaced for this rifle, which can be installed in just minutes.