Hello, original
What bullet weights are you planning to load? There an awful lot of powders that work well for the .270 (or any other powder). Based on my experience....
Moderate burn rate powders will have less muzzle blast and flash than slower burning powders that are still quite hot and at higher pressures as the bullet exits.
For 130-150 grain bullets IMR 4064, Hodgdon H4895 and Varget are all very good choices. All three powders will work well with everything from 90-160 grains bullets in a .270. The Varget and H4895 can load everything from .222 to .458 Win Mag so they are handy to have around anyway. The H4895 is likely the most versatile powder on the market. It can be used down to 60% of the highest allowable powder charge for reduced loads for practice or reducing recoil.
To develop a reduced H4895 load, check the most recent load data on the Hodgdon website and make sure the bullet weight and cartridge you want to use are listed for H4895. Then take the maximum charge of H4895 listed and multiply it by 0.6 and the result is the lowest recommended charge of H4895 for that combination. For example: where the maximum load listed for a .30-06 using a 150 grain Nosler Ballistic Tip calls for 51 grains of H4895, the lowest reduced load would be 30.6 grains. Any load between 51.0 and 30.6 grains will result in uniform ignition, pressures and velocities for this cartridge/bullet combination.
A call to Hodgdon will get you a lot more info than is on the site including bullet and powder combinations not listed.
I would not worry too much about any velocity loss from a 22" barrel as compared to say, a 24" barrel. A commonly cited figure (developed by Lyman range technicians) is that for a 150 grain .270 Win bullet as the barrel shortens from 24" down to 20" is 32 FPS. A 150 grain Nosler Partition spitzer launched at 2740 FPS impacts at 300 yards only .7" lower than one launched at 2800 FPS. Most of the debate about velocity loss seems something like pole vaulting over mouse turds.
Good luck
Lance
