Hello...thanks for the forum...I'm building a rolling block in 45-90 for longer range shoots (600 - 1000) or so and wondering what might the general consensus be for that length...looking at 1:18 twist. I may have near immediate access to a 32" but could wait a couple months for longer...not sure its worth the wait.
Opinions?
Thanks,
Tom

I have won 1000 yard matches with a rifle with a 30” barrel. My current long range rifle has a 32” barrel. No need for anything longer.
JKR

You need at least 30 inches to burn the black powder.
Longer barrels for iron sights give you a tighter angle of declination and improve your ability to sight accurately.
The twist selected means certain lengths of bullet are required for the suitable balance to achieve gyroscopic stability.
20:1 twist is more than adequate to achieve the appropriate spin of many of the longer .45 caliber bullets however the 18:1 twist will overspin many of the bullets which is desired for long range shooting to compensate for the velocity losses from drag over long distances.
However the longer barrels are attributed to foul at the muzzle more.

For long range, ( prone, not off hand, and not silhouette ), a long barrel is nice.  It puts more weight forward and rests very well on the cross sticks making a very steady rifle.  For my Shilohs with the "heavy" barrel profile I like 32" or 34".  The extra weight also tames recoil a bit which is nice in long strings.  I'm also a fan of 1:16 twist, although my 1:18 twist Borchardt in 45-90 with a very heavy 32" barrel has shot really well at long range.

With that said, my most recent long range rifle is a 16lb Shiloh with a 30" barrel, 45-100, 1:16 twist.  It is very steady on the sticks and shoots extremely well.   

Chris.

My preference is a 34" barrel for iron sights, but I wouldn't feel I was giving up much with a 32" barrel either.