It is a very common problem, especially with the surplus lacquer coated steel cartridges. If you switch to cartridges made from real brass or copper washed steel that the problem will probably go away. It is an extremely robust design, but most of the rifles available were made during WWII and are around 70 years old. They were mass produced under challenging conditions.
You could also have wear, rust, roughness or burrs causing the problem or you might just have some cooked cosmoline in it gumming up the works. The surplus rifles come packed with cosmoline which was designed to be a preservative not a lubricant. You need to be sure you have all of that completely cleaned out. If someone before you was using the rifle before they gave it a thorough cleaning there is a good chance your rifle is gummed up from that.
The other common problem is that pretty much all of the surplus ammo uses corrosive primers which requires the use of a water based solvent after every use before giving it a standard cleaning. If that extra step wasn't done regularly you could easily be having some difficulties relating to rust and pitting.
My suggestion would be to disassemble the rifle and bolt and thoroughly clean, inspect and even polish the parts especially those coming into contact with the brass, spray them liberally with some light oil such as Remington. Then reassemble it and use it with some non lacquered ammo. Chances are the rifle will start giving you good service. They were designed to take a beating and to be used under poor conditions.
This is a 1937 model. I suspected the bullet because it was a weird steel cartridge. He’ll be relieved to know. Thanks