If you want to tame an allosaur dont try to knock it out already instead build a 3 by 3 trap made by stone or wood here's what you need

9 stone foundation/wooden foundation

9 wooden ramps

36 stone door frame/wooden door frame

That's everything you need now for the building method place the foundation on a 3 by 3 formation

Then make a 3 long door frame up and place the ramps outside make sure that the ramps is attached to the 3 long door frame

Now for the taming method

You need superior kibble or diplodus kibble or raw prime meat or regular raw meat

For knock out you can use

Toxicant arrow

Tranquilizer dart

Shocking tranquilizer dart

But I recommend tranquilizer dart or toxicant arrow if your a lower level

You most likely need to get alot of narcotics depends on the dino level

And if you have a flyer mount you can lure the allo to the trap for an easy task

Welp that's the end of the tips I hope you up this for the others to see if they do not know how to tame one or two so good luck on your taming