Recoil spring problem?

[Brian Payne]

My wife purchased a custom built .38 super STI off of Gunbroker as a birthday gift. Great gun, very tight. I had a local gunsmith fit an extractor for .38 supercomp. The gun functioned perfectly at my first 3-gun match. I shoot Atlanta Arms .38 supercomp loaded to minor power factor.

The only problem or concern with the weapon was that the recoil spring really had a lot of excess flex to it. Even with the full length 2-piece guide rod, when I put the top end onto the frame I have to squish the excess spring into the spring tunnel. I have never had to do this with any other weapon but it did not appear to hamper function at all. It did seem as if the slide was difficult to unlock at times.

When I got home after the first match with this weapon, I was doing some range work and started getting light primer strikes. Checking the round showed the primer had a small dimple on it. I cleaned the firing pin chanel and that did not seem to help.

At this time I stuck in a recoil spring from a .45 1911. This spring was shorter and seemed to fit the weapon much better. The slide hand cycled much smoother and the gun seemed smoother overall, but it was stronger than the spring that came with the weapon. The empty cases only landed about a foot away from me. But oddly enough I quit having light primer strikes. I put the original recoil spring back in and the light primer strikes started again. They happen about 1 out of 20 shots fired.

I have ordered a recoil spring pack that also includes some stronger firing pin springs, and I also ordered a main spring pack that have several diffrent main springs included.

What would be causing this problem? Also, why would the gun cycle so much smoother (by hand) with the heavier (and shorter) recoil spring vs the lighter (and longer) one?

This weapon was custom built by a gunsmith that is now retired. It was built from parts from the Nowlin Custom Shop. It came with an unusual coned bushing that can be exchanged for a compensator that was included with the weapon so that you could make an open gun out of it. I do not know what weight recoil or mainsprings are in the weapon at this time.

Any help or advice is greatly appreciated.

Edited October 18, 2011 by Brian Payne

[Aircooled6racer]

Hello: Sounds like the recoil spring is binding in the frame or plug. Springs are cheap so replace them once a year. Another thing to check is if the guide rod has some wear marks in it causing the smaller diameter spring to bind on the grooves. You can check the plug for grooves also. The light strikes may be from the slide not going into battery completely or moving back from a recoil spring that is too light. Hope this helps. Thanks, Eric

[CocoBolo]

First off a spring from a 45 is probably too heavy. I would sugget getting a 10#, 9#, and 8# IMSI recoil spring and trying them to see which one you prefer. I would definately hold off on replacing the firing pin spring with a heavier spring as this will only make your light strike problem get worse. I would recommend getting a Dawson extended firing pin, this will set off heavier primers easier. You may be using harder primers than the gun was set up for. Most open guns run a 17# main spring. Swapping in a heavier main spring will likley change the trigger pull to heavier.

When trouble shooting problems with an open gun only change one thing at at time, then evaluate the difference, if it didn't cure the issue put the old part back in, and move on to the next possible cure.

Are you sure the gun is going all the way into battery, if the new extractor is hitting the barrel and holding the slide slightly open this could explain why you have light strikes, and why the heavier spring helps. Check that the barrel hood is all the way against the slide, at the top.

Most open guns have a hole in the guide rod for take down, and normally you would use a "paper clip" with a bend to capture it and leave it captured when putting the gun back together

[Brian Payne]

I picked up a pack of different recoil springs and started with the 10 lb. spring and had a few malfunctions of failing to return to battery with the new round. I then tried the 11 lb spring and it ran 100%. I did have two light primer strikes out of 50 rounds but have ordered a new Limcat XL firing pin to help with that.

This is a very tight new gun that is running in 40 degree Minnesota temperature so it might have been a cumulative problem. I will keep trying different things as I go.

Thanks for the help