I have an unusual thing happening with one rifle. It will only occasionally show velocity readings from my CED Millenium chronograph. I can shoot my 308 and 7mm/375 across the chronograph as I did yesterday with very accurate readings. Switch to a 7 Rem mag and it only occasionally will show a proper reading. I will get a value like 250.6 or maybe 2045 instead of the real velocity of 2850. Now for some details. I am using SS Remington takeoffs in 7 Rem mag for both the 7mm/375 and the 7 Rem mag. I did the rechambering myself. I set back the 7 rem mag barrel to fit a Ruger for a totally fresh chamber. Both chamberings were done with PT&G reamers. The 7 Rem mag reamer made two other 7 Rem mags that shot quite well doubt the reamer is an issue. Bore scope shows a throat with all lands the same length. If there is any issue there are some minor pitting in the rifling but my 308 has more and it shoots in the 3s. Both 7mm rifles are shooting the 180 Berger hybrid. The 7mm/375 is shooting good groups while the 7 Rem mag is shooting horrible 2-3" groups. I have switched powders with the problem rifle and it still won't read velocities but rarely and accuracy hasn't improved. I have theory. I think the 1 in 9.25 twist (haven't verified this yet) of the 7 Rem mag is not enough to stabilize the bullet at this lower velocity. I think the bullet may be crossing the chronograph with a wobble throwing off the chronograph. I have pondered this and can't imagine a bullet leaving the bore and 10 ft away having enough wobble to do this. I have considered muzzle blast but the 7mm/375 is shooting another 8-10 gr of powder the same distance from the chrono with no ill effects. I will be trying some 168 classics soon to see if the chrono issue and poor accuracy gets resolved. Any confirmation on this? Ever happen to you? Alternative theories are welcome.