I purchased a CED M2 and I am having problems. When you shoot through it it gives an error message that says it didn't pass over the stop sensor, but it gives me a speed. I was shooting some Tula steel case 223 and it was showing around 3000fps does that sound accurate. The rifle is a CMMG M4. Also I read that you can test the unit indoors by shooting rubber bands through it, so I put my infrared screens on it and I was getting good reading with no error message that way. Thanks in advance.