I am not so sure what you hope to accomplish, nor what one might look like? I have one Savage Axis rifle here - in 7.62x39 - I just took a random fired brass and dropped it into the loading port - on top of the empty detachable magazine - it fed in and chambered fine - the extractor "jumped over" the case rim and the case extracted normally.
Versus a couple of Mauser 98 here - with unaltered original military extractors - they WILL NOT close when a cartridge is dropped ahead of the extractor - they do need a single shot adaptor within the magazine - so the dropped in case starts below the extractor and the case rim slides up behind the Mauser extractor when chambering. I think the two single shot adapters for Mauser 98 that I have here, were "Score Hi" or similar brand name.