Rather than stretching the spring a better fix may be to stake on a new tube. Pins may be hanging up.

 

I'd clean out the old tube and put a new spring in it. It's one of the more inexpensive parts, can't hurt to try.

 

Your thumb may be bumping te safety during recoil/cycling.

Check the recoil spring for coul bind (stack). That will cause a harsh recoil to aggravate an already marginal condition.

Temporary measure - take the spring/pins assembly out, give sprg a stretch. Clean the spring/pins assembly and inside of the plunger tube. Lube, reinstall, shoot and wait for new parts.

 

As the gun was a kit, a previous owner could have had a plunger tube installed. Without a proper backing rod inserted into the tube, flaring the tubes legs could deform the tube bore when the legs are worked. There are reamers available from Brownells ( or were, a lot of 1911 tooling is dropping out of the catalog ) to remove any crush from the installed tube. The last tube I installed had a tad bit of crush even with the support rod inserted while upsetting the legs. That possible damage could capture the safety plunger even with a proper condition spring. Something to look for…
Joe

 

yeah, I did that once even when using the proper size mandrel (?). Now I put the shank of numbered drill bits into the plunger tube before swaging. I also bought the handled Brownells twist reamers (drills) to clean up the tubes.

 

I think I’m going to order detent spring and also recoil spring. This gun had extensive work done and maybe recoil spring isn’t stock. When I first got pistol and got it together it had safety issue. The sear was ruined by someone who watched to many cowboy movies. When you pushed off thumb safety hammer would drop to 1/2 cock. I probably didn’t need to buy a new hammer but I hated that bobbed cone hammer. I did very careful stoning on sear and a tiny bit on thumb safety when putting in new parts. The thumb safety was giving that little click when in position. I realized it’s not now. I’m taking back apart today to make sure it’s only the detent. After thinking about it , that has to be the problem. Tube - Spring or both. I’m betting that tube is problem. I will turn a brass rod to tap through tube if not a standard size, or maybe a number drill shank. Pistol as first assembled.

 

I just figured out the problem. Detent works perfect in safety on position. Went thumb safety is off the detent pin is not snapping into the dimple in safety. When safety bottoms out the detent is a few thousands above detent and it must be off a few thousands proud at rear. Safety is flush as should be but detent will not engage at any point.