Bullet: 255 gr Barnes Originals  (Barnes)

Diameter: 0.375"

 

Powder: Reloder 7 (Alliant Powder)

Starting Powder: 23.0 gr

Max Powder: 27.0 gr

 

Primer: WIN WLR

 

Case: Winchester Western

Trim Length: 2.075"

 

Cartridge Overall Length: 2.470"

 

Starting Velocity: 1,486

Starting Pressure:  

Max Velocity: 1,745

Max Pressure:  

 

*Recommend crimping case mouth into cannelure groove. *Rifle manufacturers have used a variety of bore and groove diameters in .38-55 barrels over the years. Barnes makes both .375” (# 38/5510) and .377” (# 38/5520) bullets for this cartridge. If you need assistance choosing the correct bullet, check with a qualified gunsmith or the firearm manufacturer.
Barrel: 26" with 1:18" twist.

 

Source: https://www.barnesbullets.com/wp-content/uploads/2021/05/38-55WinchesterWeb.pdf