drilling 6063 aluminum, burr on breakthrough

I could not get 1/8 x 4 flat in 6061 so they sold me 6063-t6. 3/8" hole at 2037 RPM, 16.26 i/min and I am getting a huge burr on the backside of the hole. sharpened drill, then changed to new drill, no difference. What's up?
Thank You, Randy
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Mebbe a 5/16 drill, followed by a 3/8 em. You might also find that with the straight 3/8 drill, yer hole is not perfectly round, either.
The other thing you can do, if possible, is drill stacks, mebbe stacks of 8 or more. This way, only the bottom pc is an issue. And, you'll have a rounder hole with 3/8 drill, and much greater efficiency.
I think your speeds and feeds could be ramped up, as well. Mebbe to 2038 rpm and 16.27 ipm. :) :) Seriously, I think you could easily double both.
Some alum is just crappy and gummy.

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Speed and feeds per ME Consultant program. and I am pilot drilling with a 15/64 so web thinning will not do anything. The 15/64 is used to pilot a slot which is then finished with a 3/16 mill. I seem to recall now that alum tubing drills like this too, all my al tubing is 6063.
Thank You, Randy
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centre cutting em won't work ?

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Thin the web to center.

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us underpacker.........my new word for the day.........a bottom plate