BF2S Forums Weapons Knowledge

Compression doesn't weaken a spring.  cycling compression does.

A poorly designed spring system, or poor metallurgy, or poor heat treatment can lead to relaxation of a spring under constant load.
A well designed spring system should not suffer under either cyclic loading or continuous loading.
Sometimes there are compromises due to space, cost or available materials.
Sometimes the machine is just badly designed.

In my limited experience of pistol mags the feed lips start to wear and weaken first, loading too many rounds can cause them to pop out and cause a jam.
I miss my Browning Hi Power

loubot wrote:

A fully loaded 30-mag will not jam on you.

Oh, my OP wasn't so much on 30 jamming the rifle, just whether or not 29 rounds is sometimes more preferable in performance terms.

But everyone is saying pretty much the same: quality of the mags.

Thanks again for replies guys, appreciate it.