Were they ever made with 21" barrels? I have one, and the crown looks factory, but the length seems odd.

Short answer is no 21” barrels

Pre-war catalogued barrel lengths
20” Carbine barrels
24” Standard rifle barrels.
25” 375 H&H Mag barrel
26” 220 Swift & 300 H&H Mag barrels
26” Target Gun barrels
28” Bull Gun barrels

What caliber is your gun?
What does the integral front sight ramp look like?

Great feature of 'most' prewar Model 70 model production, the integral front sight ramp! Chopping as to suggest "originality", typically requiring precision welding restoration. Known nowadays to be done, but look for rare chamberings $$$ justifying. Factory integral occurring with 'very early' production target Model 70 genre. Themselves, high collector value.

Also, the "never say never" in terms of Factory custom orders though without substantial provenance, "to buy the gun, not the story!" In respect of a 21" barrel, just the personal opinion, except as found in metric production rifles, numerically 'odd' numbers, between 16" & 30", extremely uncommon in 'other than' altered. Saying such, bowing to Winchester 375 H&H @ 25", as 'exception'!

Just my take
Best!
John

could have ordered whatever you wanted during that time! most say no records exist. Funny how they come back to comment .