If your bullets were loose or moving easy after they were seated . You did not have enough neck tension.If you are using a bushing die you will need to use a different size bushing to get the proper next tension.If it is a regular die you may have to use a different die or use a different expander ball in the die.Different lots of brass and manufactures have different specs on there brass.That's why people will use one size busing with Lapua and another size with Winchester Brass.The Winchester has a thinner case wall and the Lapua is thicker.
As far as crimping the bullet its a personal choice.Most target shooter with match bullets will not crimp a match bullet.Some re-loaders will crimp 55 Grain bullets with a cannelure.I have shot High Power for over 25 years and I have not crimped any 223 or 308.But I have enough next tension to hold bullet in place.
You can make a dummy round and feed the round several times and see if it moving if you want to check if you need to crimp.But make sure you next tension in correct first.
Hope this help.
Regards,Mike