What caliber shell does a Winchester Model 94 rifle take?

Your rifle was manufactured by Winchester as their model 121. The spent shell is removed from the chamber by action of the right and left extractors and is then bounced out by bumping agains the ejector. Look for problems there. Parts are available from gunpartscorp.com.

The model 6 Winchester wich came from the model 1890 should be actually a short, long, and long rifle .22 catridge. Which is quite intelegent design it will chamer all rounds even if you mix them up in the tube. {and if you are woundering what a .22 long, well it is the .22 long rifle shell but a .22 short bullet. the regular .22 lr. has a longer bullet.

The "parent" cartridge was the .250 Savage, necked down to .22 caliber.

The chambering will be stamped into the barrel next to or under the Winchester name.Model 1890's all had .22 caliber barrels, but they could be chambered in short, long, and long rifle (LR).You might even find one in .22 WRF (The fore runner of .22 magnum.)If there is no chambering stamped in the barrel, or it only says .22, it's chambered for the .22 short.The reason being that it was made before .22 longs and LRs were commercially available.

Winchester stopped the regular production of 20 gauge in 1963 and the 20 gauge magnum shell wasn't introduced for several years later.