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We need pics of said dual spring buffer system and pics of operating rod
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Upper and riser rail are clearanced for the spring and charging handle. Gas key slips into the charging handle block and a latch drops in to engage the key, locking it into the charging handle.
The latch can only be opened when the upper is tipped off the lower and the bolt is retracted past it's normal limit, because a notch in the spring guide rods allows the latch to come up out of the gas key.
I'll be limiting the normal bolt stroke to 2.9-3" to allow for some more compact springs. The springs are from a AR180B and are readily available. I originally planned on using a system more similar to my other bufferless uppers but the short gas system complicates things.
Gas tube/guide rod is part of the gas block. Will probably make it one piece (welded), but I could sleeve it with a replaceable gas tube insert if I felt the need.