An HK recoil guide rod is in fact shorter than a CETME's but the rod being shorter won't block the bolt travel to the rear. So changing the length of the recoil guide rod won't change anything, the tube on the HK is too short when cut off to allow the CETME cocking tube support to push the bolt back manually. And when cut off the HK tube will then slide inside the cocking tube support of the CETME . That is why you need to cut the tube off at the exact same length as the shoulder on the CETME tube, and weld the bushing on the end of the HK tube, rather than back farther like the guy in the post says. He stands the chance of his modified carrier buggering up the leading edge of the cocking tube inside his receiver, with the sleeve he welded in there going past it on it's way back. If you would like a picture I can post it.