[alaska1993]

I took my used SA to the range for the first time last week. The gun is accurate and a sweet shooter. However, the slide failed to lock back 80% of the time with Wolf ammo. I switched to range reloads and that went down to 20% of the time. The previous owner installed a reduced power recoil spring. Is that the likely source of the problem?

 

[shane45-1911]

Nope, not the recoil spring - same answer as "over there". Check your mags, or try another slide stop if possible.

 

[Griz]

I use old GI mags (I have amost 50 of them now). As I have learned, you can "tune" the mag to lock back the slide 100% of the time.

Just insert an empty mag into the gun and play with it a while to understand how the mag and slide stop interact. Then, use a pair of needle nose pliers to adjust the mag to reliably engage the slide stop.

When you are at the range, weed out any mag that malfunctions and either throw it in the pile to be worked on or "tune" it on the spot.

 

[Bob Brown]

If you find it isn't a mag follower problem, I'd have a look at the recoil spring. It sounds like it's either too heavy and the slide isn't getting back far enough, or, more likely, it's too weak and the slide is bouncing and going forward too fast for the lug on the slide stop to engage the notch.
That said, I suspect the lug on the slide stop is just a tad too short for the follower to engage.
Just remember, that recoil spring is critical to proper function. It should be the strongest spring that'll let the slide lock back on the last round every time with the chosen ammo load. If you change loads you should change the spring accordingly.

I suspect my opinion re the spring may create some heat, but it's based on over 50 years of building 1911's, and I'm stuck with it.

 

[alaska1993]

"...more likely, it's too weak and the slide is bouncing and going forward too fast for the lug on the slide stop to engage the notch."

That's what I am thinking. I'm going to give a new spring a try.

Thanks to all for your info.

Joe