Precision Scope Mounting The Remington XP-100

In the past I have worked with several Remington Model XP- 100 handguns, including a totally rebuilt model of switch-barrel status with four barrels and two bolts. The Model XP-100 is a very durable, singleshot action capable of extraordinary accuracy. Performance, of course, is directly dependent on the optical sighting system, as well as loads used and shooter technique.

The subject of this treatise involves a standard issue Remington Model XP-100 chambered for the .221 Remington Fireball cartridge first introduced in 1963. It is a shortened version of the popular .222 Remington and continues to be produced as a factory cartridge today. The XP-100 turned over to me wore a 1.3×15 Bushnell pistol scope with integral 3/8" dovetail receiver mount attached by the two front 6-48 receiver ring screws. Not exactly a setup for delivering top-notch accuracy as received.

The projected plan was to mount a 2.5-10×32 Sightron scope with a one-inch tube using a one-piece Talley Manufacturing 221 Remington Fireball with Talley Picatinny scope base, ready for fitting. Note single screw hole at top rear of receiver calling for a second screw hole. 278" forward of the existing 6-48 hole. Utmost care must be taken in locating, drilling and tapping this hole.

Talley Manufacturing. com) Picatinny Base for Remington 7, 600 (Product Number: P00252720) and 1" Tactical Ring (Black Armor) (Low) (Product Number:

This scope base compliments this space-age looking gun. BAT10L) scope rings. In tests that I have conducted I could readily demonstrate that a well-made Picatinny scope base along with well-aligned scope rings actually adds rigidity to the gun receiver while maintaining true coaxial alignment at optical center. Mounting The Scope Base The 5 3/8" Picatinny scope base spans from a point a half-inch forward of the front receiver ring to the rear of the receiver.

There were two 6-48 base screws at the front and but one 6-48 screw hole at the rear of the receiver. This base has two screw holes at the rear, spaced 0.273" apart. Measurements indicated there was ample room for a second screw hole. Here I drilled and tapped the second 6-48 hole. The procedure must be performed with utmost care and precision, and was done in the milling vise. Talley had furnished the second screw, which was very suggestive for adding it, as I did.

All went well with this phase of the work and the scope was mounted. Manipulation of the scope rings permitted optimal eye relief, which is important with a handgun delivering even moderate recoil. A safe eye relief must always be considered. Rear Action Screw Access There exists a feature about the action mounting in the stock on the Remington Model XP-100 that isn’t too well designed… at least, in my view, it isn’t.

The slotted fillister rear action screw with 82 degree head is countersunk 2.75" inward from the rear tang into the floor of the bolt channel. The screw threads into an Below and escutcheon cast into the stock. The screw passes through the slotted trigger link used to connect the finger loop of the trigger to the trigger mechanism on the underside of the stock. Both receiver guard screws pass through this slotted trigger link. There must have been some loss of sleep in this design.

Removal of this rear slotted screw in lifting the action from the stock is quite impossible without first removing the entire scope mounting system. In the process I found a way to remove the action from the stock with the scope base solidly in place.

The screw replaces the fillister head screw. Far It can be done with the scope still attached to its base or with scope removed from its base. This is performed via a screwhead-sized hole drilled through the Picatinny base and was accomplished by drilling a 3/8" hole through the base 0.850" from the rear of the base. The hole is located directly above the rear action screw for easy screw removal.

I also found it necessary to substitute the 82-degree slotted fillister screw with an 82-degree socket Considerable thinking had taken place here during development. 3×15 Bushnell with 3/8" dovetail mount attached to the front receiver ring. On bottom, the replacement scope is a 2 1/2-10×32 Sightron scope with Talley one-inch Tactical scope rings. head screw of same length.

The screw can then be removed with an Allen wrench from directly above, through the hole drilled at base center, or by reaching into the side of the cartridge loading port using quarter turns with the same wrench. I often take the action out of the stock to thoroughly clean the firearm or make other adjustments. If the option to conveniently remove the scope and reattach it to the Picatinny rail is used, the gun will still remain sighted as the scope rings are locked back on the rail in the rail slots.

Final Testing In the accuracy testing process of any gun, nothing is written in stone. Each gun can be quite different from another. Sometimes the end result can be hard to predict. In the load and accuracy development of various scoped pistols, I had designed and built a special pistol rest. Properly used, it pretty much eliminates any human error

221 Remington Fireball shows a well-balanced gun weighing 4 pounds, 14 ounces with the 2 1/2-10 Sightron scope equipped with Talley Tactical scope rings on a Picatinny base. The old gun dates back more than a half century. A good pistol rest is an absolute must in delivering best pistol accuracy in load development. in testing. As shown in the pictures, the fully adjustable rest supports the underside of the pistol butt and/or barrel or forend.

The upward and rearward recoil allows the gun to settle back into the Load development is the final proof of a gunsmith’s efforts. 349" average for three five-shot groups from a 10-inch barrel would better the performance of many good rifles. A quality optic mounted properly makes this handgun shine. two sand bags shot-toshot. In testing the XP- 100 .221 Fireball, I used a variety of loads with very encouraging outcome.

In one series of three five-shot groups at 50 yards using 52 grain Berger bullets, the groups me a su red 0.415", 0.362" and 0.272" for a 0.349" three-group average. I have tested some pretty expensive rifles that wouldn’t do this well. In my own experience, the changes I have shown here have made this already fine, old gun easier to work with in delivering superb accuracy and performance. Revisiting the venerable old gun and cartridge has been a pleasure.

Sometimes as gunsmiths, just another close look at our work can be very fulfilling and this was one of those times. AG