I’m starting at 19 grains of 4227 and loading to 1.65 inches COL.
First off, those rounds are over industry standard max length, which is 1.610".
A revolver won't care, but a magazine fed repeater might, as they don't have a lot of extra room in the mechanism. Marlin lever guns in particular are well known for not working well with overlength ammo.
What gun(s) are you using that load in??
Its been 30 years or so,but as I recall,the bullet snags the chamber mouth and won't go in.
At the same time,another round has fed from the tubular magazine to the lifters,so you have sort of a double feed.
This isn't quite correct, at least not with the guns i am familiar with. I am quite familiar with SWC slugs "hanging up" in a lever gun during chambering, and it can and does happen with regular length rounds, as well.
What sometimes happens is the round on the lifter "bounces" out of proper alignment with the chamber and the bullet catches on the edge of the chamber and doesn't slide in.
When this happens, bump the lever forward just a bit (some say "wiggle" the lever). This take the pressure jamming things off the cartridge and it will usually then drop back into proper position for smooth feeding. Trying to force the round into the chamber is the wrong approach. Back it off, just a little, and then (usually) it will go in smoothly when you close the action.
I have often done this, done right, it works.
If your rifle is in proper working order, you don't get a second round fed on to the lifter if the action is jammed open due to a SWC getting "stuck" on the chamber edge. At that point, the lifter is still "up". It doesn't drop down to reecive the next round until the bolt goes far enough forward, and that chambers the round.
With some guns the user can create the double feed jam by incorrectly working the action when a round sticks on its way into the chamber, by opening the bolt far enough to let the lifter drop but not far enough to eject the round.
A defective cartridge stop can also create a jam, if it releases a round while the lifter is still UP.
Seat your Keith style to the crimp groove and measure over all length. It ought to be 1.610" or less. Compressed powder charges are not automatically a bad thing.
Also don't fret over a tiny difference in bullet weight. A cast bullet weight can/will vary depending on the specific alloy it is made of. You will not be eaten by dragons if your bullet is a few grains heavier or lighter than the nominal weight listed in the data.