Ok folks let me start off by saying I just got it today and have not shot it yet. It is a shield 2.0 45acp. It is used and has 2 6 round magazines, one with new follower and the other has the old. Gun looks to be hardly shot by looking at barrel and rail lack of wear. Here is the issue, the magazine with new style follower will (most of the time) lock the slide back when you have it inserted and pull it back. The other magazine with the old style follower will hardly lock the slide back unless you push up on the base plate. I have made sure both magazines were completely inserted. Any ideas? I can see the slide stop not fully going up so I am thinking maybe order from wolff a 5% extra power magazine spring and maybe all new followers. Or just try a new 7 round magazine.

I'm thinking the mag spring as well. I think the extra powered one will fix it.

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Get rid of the old follower immediately. In the morning, call S&W customer service and request a new one. They will send you a new updated one for free. The old follower has a tendency to create failures to feed, so you won't want to carry it. When you're replacing the old follower, be sure the new one is attached and oriented correctly on the top of the spring. Shield 45 magazine springs are quite robust, and I'd be surprised if you needed a "stronger" one. A new follower should fix it. I have over 7,000 rounds through my Shield 45, so I have some experience with it and its magazines. It's a great gun, and you're going to enjoy yours.

Welcome to the Forum!

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What, me worry?

I agree with SWSIG, I would also go one step further. Disassemble both mags and compare the length of the springs to make sure that the malfunctioning mag has not had the spring "clipped" to make the mag easier to load. If the faulty mag spring is shorter than the working mag, you might as well see if you can get S&W to send a new mag spring also. I frequently see the advise given to just clip a few coils off because the mag is a little difficult to load, it won't hurt anything, ABSOLUTELY WRONG. Get a loading assist device if you need to but please don't shorten the springs.

Just make sure you have new followers in all your mags. No need for extra power springs.
Or a spring change, unless, as mckenny pointed out, the previous owner had shortened one of the springs.

Everyone's hands and grip preference is different, but those 6 round mags just feel too short for me, I prefer the 7 rounders.

I did put on a metal "pinkie" extension from NDZ Performance on my 6 rounder, and it helps the grip feel more substantial, without adding length to the top of the gun when holstered.

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U. S. Army Veteran

Dissambled magazines and both springs were of equal length. New follower came in today and it definitely fixed the issue of the slide not locking open when I manually pull it back. Thanks for the help.