Soda Blasting

[Caster]

So, I needed to strip my upper (AR) receiver but I didn't want to use chemicals or embed media like sand or glass where the bolt rides, so I thought I would give baking soda a run. Never tried it, but less than $2 for a large box what the hey. IT WORKS AWESOME!!!!! Looks like it just come out of the machine tool that made it! Baking soda dissolves in water so a quick rinse and there's no worries about particulates coming out later and galling anywhere. I used less than half a box, so it cost me a buck to strip the upper CLEAN.

Bad news. The upper I picked up second hand has a crack I would have never known about. Had I sandblasted it, it would have likely not shown because the aluminum being so soft, it would have likely peened and hid it. I've seen that happen before. The crack would likely never manifest into an issue, but me being the paranoiac that I am....It's dead to me. It's at the rear where the head of the charging handle rests. I can see in a vision of my own demise; The entire top coming off during a catastrophic failure.

Would that ever happen to anyone? No not likely. Would that ever happen to Caster? Undoubtedly. Added a Yankee Hill upper to my wish list at Midway USA.

Two lessons learned today. One - Baking soda ROCKS for stripping finishes. Two - Always buy new parts when building a rifle you intend to stake your life upon during the impending zombie invasion.

...add to that my stomach ulcer is acting up and I can't drink, it's raining and I can't go outside and play. Sunday Sept 4 SUCKS!

I dunno if you can see it, but I circled the crack with a marker:

[Westwindmike]

My dentist uses a baking soda blaster on my teeth. Works good there too!

[Dolomite_supafly]

Use it for a dedicated rimfire upper to train with.

It almost looks like it has endured a kaboom at some point in its life. I can think of no other reason why there would be cracks in that area. Or perhaps a round was stuck in the chamber and they used a rubber mallet on the charging handle to get it out.

Do you know what upper that is supposed to be? It is an odd mark that I have never seen before. Actually it looks like it was from the Cardinal forge.

Dolomite

[Caster]

No I don't know anything about it's origins. I know it's been around a while. It's been in a box of parts in an older gentleman I trade around with; Out in his shop for longer than I have been into AR's.

The little symbol there is it's only marking. The dedicated .22 upper makes sense. I guess I'll hang on to it for now.

[Caster]

Here's a better look at it.

[Trekbike]

This maybe a dumb question but couldn't it be welded up and remachined? I'm not an AR person but it doesn't look like that part of the upper doesn't see gas pressure but I may be wrong.

[Caster]

Oh anything CAN be fixed, but I can get a new Yankee Hill for under a hundred. It just ain't worth it.