Sigma 120-400 - any good for motorsport?

I currently shoot with a 55-250, and while I'm getting some images that I'm happy with, they are nowhere near the quality of others on here.

Although something like a 100-400L, or a 400 prime would be nice, my budget doesn't really stretch that far

I've seen that Sigma do a 120-400, which although has the same F-stop range, does give me more length, which will must help? Also it is a lot cheaper, basically, and I wondered if it is any good for motorsport? Does anyone hear use currently, or has used one and can give any feedback on it?

Thanks in advance.

I don't have the Sigma 120-400 but below are two of my favourite photos taken with the Sigma 150-500mm.

Both the Sigma lenses are significantly heavier than the lens you are used to and if you haven't used a long telephoto before you will most likely find that you need to improve your technique to get the best out of the lens.

I believe the Sigma 120-400 will give similar results to these photos. Hope this helps.

200mm

Thanks for the info and the images.

Goot point about the weight of the lens, although I do have a monopod that doesn't really get used at the moment. As you say my current set up is pretty light.

I'd suggest considering a Sigma 100-300 EX as well.

I have this lens, it´s not bad for motorsports, however the long end is not very sharp on f/5.6 so you need to use narrower aperture (if possible, at least f/7.1). Below you can see examples how it works in bad conditions (higher ISO, F/5.6) an how it works in ideal conditions (ISO 100, f/10). Both photos taken with Canon EOS 40D.

Thanks for the input & the images everyone. Certainly food for thought.