H&r plainsman spring for magazine

I have an h&r plainsman model 865 bolt action rifle, 5 round magazine, .22 caliber. First time i try to load it the first 4 rounds load, but when i tried to load the 5th the bottom popped off & the spring sprang to who knows where. (I was outside). Am i better off replacing the spring or the entire magazine? The spring is the only part missing. Your assistance would be appreciated.

I wonder whether having the bottom pop off was a freak one-time occurrence or if it indicates that the bottom piece us worn out and it will keep happening.