Re: .25-06 VS .243
I own a 25-06 in a Ruger MkII Varmit, it shoots the 85 Nosler BT's at up to 3700 fps, but is not very accurate bast 3400 fps.
I use the Berger 115 VLD's at 3200 fps, and can get avg less than an unch at 200 yards if I let the bbl cool 3-4 minutes between shots, about 1 moa if I don't let it cool
Berger VLD's are this jecket bullets, perfect for coyote sized targets.
Now the 243 vs 25-06 is a good debate, for varmits, I'd opt for a 6mm or 243 for maximum knockdown power at range...
Lets compare REAL life here
243 and 25-06 with a 26 inch bbl
243 gets 3100-3150 fps with a 105 Berger BC 565
25-06 gets 3150-3200 fps with a 115 Gerger bc 522
Add another 50-75 fps for the 6mm rem
You can see that the 24 bore will launch a better BC bullet at close to or more velocity, wich means more bullet expansion at longer ranges,
the 6mm (.243) also has a Berger 115 VLD at .597 bc, but you need a 1:7 twist in a 243 or 6mm rem, 8 twist in a 6-284
also, the best fast bullet for the 25 bore is the 85 grain Nosler BT with a BC of .331, the 75 grain V-max has only a .290 bc, the .243 cal 87 Grain V-max has an outstanding .400 BC, the 6mm or 243 bore has way more bullets selections
For large deer, the bigger cal is better of course, but for varmits, fast flat shooting light jacket bullets are it,
the 25-06 still is good, but not a lot of bullets to chose from.
I think the 24-25 bores are better for varmits that the bigger and smaller bores.
a 22-250 with a 55 bt would probably stop a coyote more often that a 30-06 with any bullet, sometimes smaller and faster is stronger.
but 22's do not have very good bc bullets, for example
a 25-06 with 115 at 3200 ffps muzzle, is moving 2000 fps at 600 yards with the light jacket Berger, it is a much better choice that a 220 swift with a 40 at 4000 that is half as fast by 600 yards.
Either will do you good.