Welcome to ECF, Brightboy...
More information would be good... clones or authentics? Battery brand / type? Have a dial or digital caliper to provide accurate measurements? Remember... the more specific information we have, the more likely we'll be able to solve your problem.
Genuine Colonials have a telescoping top 510 pin. Put the atty on the top cap first - flush - screw the outer 210 contact firm to the atty - then the inner 510 contact in as far as it goes, but not tight. Install the battery, then the top cap.
Does the battery rattle? Yes? Good. Remove the top cap/atty assembly and screw out the inner 510 pin the amount you think will take up the free play. When the top cap is flush, and you have no battery free play... you're done. ;-)
No battery rattle, and you can't screw the 510 top cap to seat in the tube? Get a shorter battery or file down the 510 a bit shorter.
Still no go? I don't see it often, but it may be that your 510 pin insulator is too long, preventing everything from seating flush. It's typically easier to shorten the upper, smaller diameter end.
Even more rare, the insulator is not
threaded or "snapped" in all the way. Check that too.
That's about it.
