Have you ever lubed/cleaned it?

Clean it well and lube it well. The rails and locking block should be wet with oil.

Also, as you said it was used, I would replace the recoil spring.

Also, can you tell if it was 1 mag or all of them? You may need a new mag or mag spring. Also, are these factory mags or aftermarket ones?

And, was this factory ammo or reloads?

Odds are the problem is one of the items in Shipwreck's list.

I agree with the above suggestions.

I would not switch to a high pressure round.

Originally Posted by Shipwreck

Have you ever lubed/cleaned it?

Clean it well and lube it well.

First things I thought of. Should have been done before the first thought of going to the range.

My cleaning supplies are in shipment to my house, and I will clean it thoroughly upon arrival. Mags are factory, and I was swapping between the two of them after each mag shot. I was shooting Federal FMJ, which is pretty reliable ammo to my knowledge. I have another recoil spring on the way, but i'm hoping it just needs to be cleaned/oiled. Thanks for the help, and keep it coming.
-DWhite

Ok, the ammo should be good.

Clean and oil it and change the recoil spring. Then, go try it and if it still happens, see if you can isolate it to a certain magazine

The only other thing that may come into play,is "Limp Wristing".It's one of those
things that people just don't think about.The shooter gets too comfortable and holds a loose grip.
Some firearms could care less.They'll operate no matter what.Some are finiky.
I actually push the weapon forward,toward the target,while sqeezing the trigger.
Just a thought.

I know that we were not limpwristing it, so ill start with cleaning it and changing the recoil spring.
-DWhite