Smith & Wesson gave me a complete part #264380000 which I believe to be the spring and guide rod.

The heavy spring #24298 and the lighter spring #20071.These numbers may be followed by four zeros. #242980000

I only had the lighter spring in my 945-1 once and it would not go into battery. At the time the gun was new and tight.

I always run the heavy spring and it works even with 185 grain bullets and reduced powder charges.

I also have a 745 and I purchased a replacement spring through Midway labeled for the whole .45 series of guns.#227209

The spring was longer than the original and very stiff. It still functions perfectly with full power and reduced loads and it may be GTG in the 945 as well.

Bruce