It's not uncommon to purchase a pair or western boots and have the shaft fit a bit too tightly, or even so tight they can't be pulled over the calf. When this occurs, there's an easy solution that will enable you to stretch the shaft to the appropriate size that is comfortable.
Test a small spot of leather on your boot by spraying the inside of it with a shoe stretcher liquid. Stretcher liquid is used to relax the fibres enabling the leather to stretch without breaking the fibres. Some liquids might make the dye in the leather run. If the colour runs, try another brand.
Lightly spray the inside of the shaft with the stretcher liquid. It is not necessary to soak the leather, but you want to lightly dampen it to loosen up the fibres in the leather so they stretch instead of break. Boot shaft stretchers have a long mechanism that expands to fit the entire length of the boot shaft snugly. Place the boot shaft stretcher into the boot and turn the stretcher handle until the stretcher begins to put pressure on the shaft of the boot slightly stretching the leather. Do not overstretch the leather. Leave the boots to stretch overnight in a warm, dry location.
Release the handle on the boot shaft stretcher until you can easily pull it out of the boot. Try on the boot on to determine if the shaft is stretched enough. If it needs to be stretched more, repeat the process until the correct fit is attained.
Boot shaft stretchers can be expensive running around £97 or more. If you are not in constant need of your boots being stretched, many shoe repair stores offer this service for a minimal cost. Some shoe retailers also offer this, e.g. if you purchase your boots from Nordstrom, they will stretch the shaft for your if needed at the time of the sale.