Originally posted by apocalypse.v The 300mm is good but images are not sharp enough. I would like to use it for sports and wild life photography. Hope the info helps you suggest me good options.
I think I left out another very important aspect: your budget.
You have two groups of options: A prime lens (fixed focal length at 300mm) or a zoom that reaches at 300mm.
Generally speaking, primes will give you better quality images, will be faster and will cost more. Zooms are much more flexible, cost usually less and some of them are quite good.
If you are comfortable using Manual focus that will open a lot of inexpensive options, but trying to do sports and wild life on the move, it will most likely require to use auto focus. For sports, shutter speed is important so you need a fast lens. You can increase the ISO of course but a faster lens will give you more options. Another consideration is if you plan to use a tripod/monopod at all times. Most fast primes (and fast zooms) are too heavy for comfortable handheld photography.
If it is within your budget and want to go the prime way, then the Pentax DA-300mm F4 may be a good choice.
If you gravitate toward a zoom (which will be my recommendation) the Pentax DA 55-300mm is very good at 300mm even wide open at F5.8 and costs very little. Along with the kit lens (18-55) makes a very good compact travel kit that you can take it anywhere.
There are other choices for zooms that will reach 300mm from Tamron and Sigma, but the DA 55-300 will give you the best value.
Another thing to remember is shooting at 300mm is not easy. Even with SR on, you need to maintain a fairly high speed (at least 1/200) and use some support (e.g. a monopod). Use as high ISO as you can stand the noise. A grainier picture is better than a fuzzy one.