Originally Posted by yannotti
I think it's a stock tube from a bushmaster but I can't find any markings
Back in the day I bought my Bushmaster from Skirmish the Store in Reseda, so I got a choice of tubes so I don't quite remember which one came stock with most guns. But this is a wild guess and I think it was a #2.
The larger sized tubes had some instances of breakage at the base, so I usually had a couple extra. Plus back before adjustable bolts became the norm, adjusting the velocity using different spring and tube combos was the way most people changed their gun's velocity.