So I actually need a 357XP piston, and thought I'd see about the LilRedBarn popup jobbie. I also hedged my bets and bought a Meteor. I took a bunch of crappy cell phone pics in case it helps anyone. My mics are at work so I can't measure tolerances. I'm too lazy to pull out my digital scale and weigh them right now. The OEM piston is out in the garage still on the crank so no comparison to that right now either. The LilRedBarn is more expensive than Meteor, but I really think it should be the other way around.
First pic is the LilRedBarn (top) and the Meteor (bottom) side by side. The machining on the LilRedBarn piston top is more pronounced. If you run your fingernail over the surface grooves the LilRedBarn is louder than the meteor. That comes from running a tool at faster feeds and speeds. It produces more of a roughing cut than a finish cut. The finish is finer, and in my opinion nicer, on the Meteor. However, this probably will make zero difference in how it runs.
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Next up is the side profile of the LilRedBarn. The finish continues down the side of the piston skirt. It might actually be an advantage to hold oil better, I don't know. On the sides of the piston below the piston pin bore, the bottom edge of the piston skirt looks like it was hand-finished with a grinder, as evidenced by what looks like chatter; it doesn't look like a uniform CNC machining job. The inside surfaces of the piston pin bore boss (toward the center of the piston) are non machined. The unmachined cast area on the outside of the piston around the piston pin bore has micro-chips at the edges where it meets the machined wall indicative of dull tooling being used.
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The next picture is the Meteor. The smooth finish continues down the side walls of the piston skirt. The un-machined casting around the pin bore looks better to me than the LilRedBarn. The inside surface of the piston pin bore boss is machined. The bottom edge of the piston on the sides is not finished by hand or machine, but the machining of the piston skirt left no noticeable burr that necessitates chamfering that edge.
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Here is the bottom of the LilRedBarn. The entire bottom edge of the piston is un-machined raw casting. There is casting flash on the pin bore boss (bottom side boss in the photo) because it is an unmachined surface. The casting has a dull finish.
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And here is the bottom of the Meteor. The bottom of the front and back skirt is machined. As mentioned before, the inside bosses of the pin bore are machined. In general the cast aluminum has more of a gloss finish to it.
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