...... but aluminum your only working with 5-10lbs pressure to avoid blasting of anodization right?......
Depending on the type of anodizing, it runs from less than .001" thick up to about .003" thick for hardcoat anodizing. I would expect aluminum-alloy firearm parts to be quite thin. Grit blasting WILL remove the anodized surface, thereby removing the corrosion protection.
For a quick explanation of different types of anodizing, do a search for "Pioneer Metal Finishing".... before I retired, we had them treat a lot of our aluminum products for corrosion protection, abrasion resistance, lubricity, etc. Their website has (or had, anyhow) some good information. Wikipedia is another good source.
You could, after grit blasting, have the part re-anodized; it is a surprisingly inexpensive process.