Yes. A GLOCK can be built to be competitive. You're generally gonna dump a ton of $ and/or time onto an Open gun anyways, so do what you like. I've seen people run CZ75s and Witnesses and be competitive when others said it couldn't be done. If the gun is done right, sure. I think more than anything though, YOU have to be willing to put the time in, regardless of the platform of the gun. Open class is usually no joke, so as long as you're in it to win it, I think you're okay to pick whatever you want to build on for the most part. Especially with all the aftermarkete support for the GLOCK.