Since you say it's nice and smooth...you could probably just run it, but....

The rear bearing on the .70 is a common bearing, that is easy to get from just about any industrial parts supplier. You can get a top quality part for around $10. If you're so inclined...just replace it.

If you'd like the specs on the bearing...I'll try and dig one out.

'Race

**EDIT**

The part is an NTN 16002 bearing (or SKF equiv). Dimensions are: OD: 31mm, ID: 11mm, Width: 7mm.

Don't waste money on shielded/sealed bearings. A plain, open face bearing is ideal for this application.