pmi razzor barrel for 98c

[keyhead]

Can anyone tell me if these pmi barrels need an o-ring at the end where the threads are, I got a new razzor and there is no oring and when i screw it in there is some wobble. Anyway to fix this? Or is it just cause no Oring?

[cocker kid 2k2]

You prolly need an oring, but thats odd, even though there is no oring doesnt mean it should wobble.