[Troy800]

I don't know much about the 25-06 but I use the Berger twist rate stability calculator.  If you get some bullet data from the manufacturer website and plug it in it will give you a stability factor.  Doesn't mean the bullet will be accurate but can help you with twist rate.

[Troy800]

I'm no expert on the 30-06 so you only get my 1 cent worth.  That rifle shows a 11″ twist rate so it is going to like the lighter.  Based on stability alone I would stay under 185 grain for jacketed and lighter for all copper. But with that said just because a bullit is within its stability range does not mean it will be accurate, only means it is stable.  The T3 light has a thinner barrel which means it is a little more sensitive to harmonics.  When you buy off the shelf ammo you are limited but I would stay under 185 gr and try bullets with different speed or fps.

[Troy800]

No I don't think you ruined it.  I will tell you my experience with the T3 molded stock and take what you can from it.  I bought the T3 243 for my daughter.  I couldn't get it to shoot sub MOA.  Here are some modifications that I made.
–free floated the barrel
–bought an aluminum trigger guard. (The plastic one with washers was very sensitive to torque)
–bedded the barrel with aluminum pillar blocks and SS recoil lug
–use right bullet.  The 243 had a slower twist rate and did not like the heavier bullets I used at first.

I'm not sure what the made the most differance but think it was bullet selection.  I went from 2″ groups with 95 gr bullets to .8″ groups with 90 gr bullet or lighter.