Carlos,
They do and the machined units are more forgiving... But I have been able to get them all to work eventually. DaninAlaska just ordered a bunch of them, a LA for me and he got a couple SA followers... They were all the same length... I got my LA though!
When the cartridges start rocking in the magazine it is time to look at the magazine box lips farther back.
The click Geo described and the return of the problem is likely the box popping back out of proper alignment in the action...
art
