NO GUNSMITH INSTALLATION. ANYONE can do it...... just unscrew the hex nut the grip or buttstock attaches to and the old spring and strut drop out.
Highly recommended if a hammer extension is installed.
TC Encore and G2 use the same hammer spring.
The factory hammer spring is simply marginal at best.
Avoid misfires and get better accuracy with a stronger hammer spring, especially if you use a hammer extension.
NOTE: Thompson Center states clearly that you will likely get misfires with a hammer extension with their standard hammer spring, admitting in effect their hammer spring is marginal
If you use a hammer extension, in most instances you MUST use a stronger hammer spring also.