The secret to any of the spray and bakes is PREP.  One, you have to degrease well.  Then SAND BLAST - you need the 'tooth' that sand blasting raises - BEAD BLASTING will give poor results.  You do have to be aware that different metals require different amounts of pressure when blasting so you dont screw up dimensions - doesnt really matter on and AR exterior.

The other secret is parkerizing first for steel.  Parking is a PITA, so I use K-phos.

This stuff will chip on sharp edges so you gotta round them a bit - same places that where from holster carry on pistols.  The spray and bakes arent perfect but they far exceed everything else and are on par with the mix hardener and spray systems.

So my process - and this has worked on AK's, AR's, bolt guns, beltfeds (and it survived me throwing my mg 42 off Jason's deck when if would run) is:

Brake sharp edges with a file/sand paper to promote adhesion
Degrease
Heat (check for more grease oil running out - degrease again as needed and repeat until nothing runs out - AK's take 2-3 cycles).
Sand blast 60-80 psi, fine media
hig pressure air blast to get sand and dust off - you may need to whip the part(s) down with MEK or acetone to get them perfectly clean.
K-phos - keeps parts from flash rusting while your doing other parts also gives a good substrate for paint to bond to.
Heat
spray
bake
reassemble
abuse

One option Ive used to sandblasting (especially on those really tiny parts) is to rough them up with some 400 grit sand paper before spraying - it works well.

Looks good - just get ready to do more of your stuff once you see how well it holds up.