A questioner said:
Small metal dart found in yard. Located in Northeast USA. “Nose” is threaded but doesn’t completely screw off. No stamps or markings.

More info from the questioner:
Small metal dart found in yard located in Northeast USA. Nose is threaded but does not screw off of body. No markings or stamps, was not there in the fall.

Some of the people opinions on it:

Minimum-Zucchini-732: “Haven’t seen one of these in a while. Likely Kid’s toy – you put a cap in the end, throw it, and it pops on landing.”

prairieson2644: “It’s an old ‘cap dart/grenade’. Red paper ‘caps’ were inserted in the space, and when thrown would bang on impact.”

gty2269: “Weird just talking to someone about these the other day. They still sell them here.”

Magicwandza: “Kids toy. You put those paper ‘bangers’ underneath the spring and throw it on a hard surface to make it bang. Same principle as the old pop guns with the paper banger ‘ribbons’.”

Budget_Roof1065: “Cap bomb. I must have gone through a hundred of those as a child in the 70’s. Twist the top, put a paper cap in, twist the top back down, throw it up in the air. When it hits the pavement, it makes a bang.”

aztecforlife: “We stuck caps (little explosive wad) in them and they pop when you throw them. Probably removed from the market around the time lawn darts were deemed hazardous.”

JimiTrucks1972: “I had a bunch of those. Man I can smell the picture. God I loved the smell of those red caps.”