The 20gr result was a bit odd. It had a hi value of 1277 ft/s and a lo value of 1040 ft/s and everything in between, hence the low average.
That's a chronograph error of some sort, I'd bet.
You should be at least 10, more like 15, feet from the chrony. 15 feet is pretty much "the" standard.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.