I'd guess that with longer than 22" tubes (on 06's) that one could go to 28 plus. But in the normal 22" tubes I've found that I can get to 2800 and then some if I push it, but I've had to push it harder than I prefer to get there.
When I was younger I'd of pushed it to get there but as I've gotten more mature (aka older) for me it's just not worth it. Give me a LRF, dotz, or turrets and I'll get there just fine without pushing it.
Dober
