before giving them the Perma-silk treatment? I have access to a sandblaster, and wanted to know if this would provide an even better finish than just washing them with soap and water. Thanks.

I would think that sandblasting could end up doing more harm than good if you weren't very, very careful.  I washed mine with an SOS pad and warm water it stripped off the old finish completely.  It only took a minute or two per mag and they came out great.  

IMHO using an SOS pad will give you the same result as sandblasting but without the risk.

Sandblasting mags is an ultimately stupid idea.

You'll lose the anodizing if you do that, and you'll be left with magazines that have very little scratch and wear resistance.  

Just clean 'em.  Don't use anything abrasive on them, and then apply permaslik or whatever.

CJ

At MOST, I would use a very low pressure walnut hull blast.  AT MOST. You WANT the anodizing, or if they're really old, the alodyne coating.

Heed the advice from the others. Don't do it.

Meplat-

Do not blast the mags.  As others have said, it will remove the anodizing (electrochemical conversion of the surface of the aluminum to aluminum oxide, provides corrosion protection).

The hot water and Dawn wash followed by a wipedown out in the open with acetone or methyl ethyl ketone is the most that you would need.  The solvent wipe will remove any loosely-bonded remaining Permaslik, and if you wipe enough it will remove most of it.

Noah

Ok, just a thought. Not a good one, but a thought non-the-less. I try not to do it much, it hurts my brain.