When I started doing front squats, I was squatting 225 and I couldn't even front squat 135. It took me about a month or two two develope wrist flexibility and keep my elbows high. Now my front squat is increasing faster than my back squat. I back squat 275 and front squat 205. So I think you just need to get used to the exercise and then your numbers will increase. To answer your question I don't think it is very common for someone to front squat less than 50% of there back squat. Do you use a clean grip or cross your arms?