I just changed out the front sight on my LW Commander and it shoots dead on @30 feet. You can order sights from Brownells for about $6.00 plus freight. Some things to consider.
1. At what range are you shooting at and are you using a proper grip? Sounds silly but without a proper grip it can affect your accuracy.
2. What bullet are you using? Heavier bullets will fly higher than a 185SWC over a 230grn RN. Try to use some factory loads @ a specific distance and use the supported position. If you have or can borrow a bag rest, use it and fire 5 rounds, move it back another 5 feet and see if the height changes. Keep doing this until you are at your desired shooting distance. I would start @15 feet and move using 5 foot increments until you are out to 40 feet. See how much the height changes whether it be high or low.
3. Use Dawson's website that Jim gave you to measure your height and how much you can change it. It is hard to measure the height of the site BUT it will give you an indicator of where you need to go as far as sight changes. Fusion sights have different sight heights they recommend BUT they are NOT Novak sights, they are knock offs. The show a higher sight for the Commander over the full size.
4. If you are shooting low, and after your measurements, you can use a dremell or a file to very gradually lower the front sight. After quite a few months I finally got mine worked out but it can be a pain in trying to figure out how to get it to shoot @POA, of which I assume to are trying to achieve.
5. Remember if you are shooting low, then LOWER your front sight! If it gets too low then you will have to change out your rear sights and that's is where the expense really adds up. If all else fails, write down everything you did, completely document everything you done, and then call Ruger CS and give them all the facts. Ask for a technician and give a complete explanation of what is happening and what you have done or what you are doing.
6. Finally- make sure you are using the front sight when you shoot!!! When aiming, the front sight should be clear, rear sight will be a little blurry and your target will be blurry. Concentrate on using the front sight consistently when you are firing. So many people try to make sure the front and rear sight are clear when they shoot. This is not the correct way. Where ever you put that front sight is where your bullet will land. So many people think that they have to have a clear sight picture on the front and rear and wonder why they are not hitting at POA.
I hope this will help you clarify your problem. I worked diligently for 4-5 months on mine to get it correct. Part of it was me and part of it was the sight. That little white dot on Ruger sights are hard to see with these old eyes of mine, but I now have complete confidence on where my bullet is going to land.
Good luck!!!!
Tommy