Modifying the Thompson/Cente TCR ’83 Trigger for Field Use

With its set trigger, the Thompson/Center TCR ’83 singleshot rifle is easy to shoot and extremely accurate’especially when shooting from bench rest. But for field use and hunting, at just over a pound, the trigger is a bit too light. The rifle can be fired with the trigger in the unset position, which the owner’s manual suggests is suitable for hunting.

But with a pull weight at this stage of about 7 pounds, most shooters would find this to be too heavy for field shooting and hunting, Installing an Auxiliary Spring Fortunately’and this is obviously something you won’t find in the owner’s manual’t he TCR ’83s set trigger can easily be altered to a satisfactory hunting pull weight in just minutes with the installation of a small spring.

Right top: This underside view of the trigger guard and set trigger used on the TCR’83 rifle shows the sear-engagement adjusting screw, as well as the slot (arrow) used by the author for an auxiliary spring to increase trigger pull. When the adjusting screw is turned inward, the sear let-off is more sensitive. Right bottom: The auxiliary trigger spring is seen in position at the rear of the trigger.

When turned outward, the set screw between the triggers increases trigger-sear travel, which makes the trigger seem to pull heavier.

On top of the gauge is the spring used to increase trigger pull. In order to prove his point, the author insisted we include this gratuitous photo of himself, the altered Thompson/Center TCR rifle, and his trophy whitetail buck. However, the adjustment does not directly increase or decrease the pull weight. Rather it regulates the amount of let-off travel when the rifle is being fired with the trigger in the set position.

Thus, this part of the set trigger adjustment involves sear/trigger engagement, and not pull force. On close inspection of the Thompson/Center rifle, you’ll see a small space immediately behind the base of the trigger and the upper aspect of the trigger guard. This rectangular space is 0.187 inch in length by about 0.130 inch wide, providing ample room for a flat compression spring to fit in this space.

The margins of both surfaces are perfectly square and are perfectly suitable for the application of a compression spring. If such a spring is made perfectly square, tension holds it in place as it works to increase trigger-pull force. To accomplish this, I found a spring that fit nicely into the T/C’s 0.130inch opening. The opening provides ample length to easily push a compressed spring into position.

I was able to push the spring into place with my fingers and it remains firmly wedged against the opposing surfaces during shooting. While installing the spring, I also increased the amount of trigger/sear let-off travel by turning the adjusting screw counterclockwise a full turn. This gives the hunter a feeling of increased trigger pull by itself, although this let-off adjustment alone only serves to adjust triggersear travel.

Conclusion Increasing trigger pull force from 1.2 pounds to just over 2 pounds on the Thompson/Center TCR ’83 single-shot rifle makes it a safer and better hunting rifle. The greater the spring strength, the more difference will be noted on the trigger pull. This minor conversion is easily accomplished, for a few minutes of time and the price of a small spring. When not needed, the spring is easily removed and stored for later use.

But for those who enjoy shooting a set trigger and prefer a little more pull weight, the auxiliary spring can be left in place at all times. I