L4 mag issues

[Joe H]

but never understood the part about taking up space with the recoil spring inside the butt

AER,

When you introduce the striker into the recoiling parts behind the bolt the full compression of recoil springs is less than the full design compression by the length of the striker. The bolt travel is less than design by the length of the striker. Since the return rod bears on the bolt, the springs cannot be fully compressed. The addition of a plug ,the length of the striker, behind the roil springs assures full design compression of the recoil springs with the striker in place. Hope this explains it.

Joe